Download PDF
Synthesis 2020; 52(08): 1287-1300
DOI: 10.1055/s-0039-1690050
paper
© Georg Thieme Verlag Stuttgart · New York

Oligoether-Substituted Derivatives of Carbon-Rich 1,4,7,10,13,16-Hexaethynyltribenzo[a,e,i]cyclododeca-5,11,17-triyne (C36H12) and 1,4,9,12-Tetrakis(ethynyl)dibenzo[a,g]cyclododeca-5,7,13,15-tetrayne (C28H8): Potential Precursors to the Circular [6]Phenylene (‘Antikekulene’) Frame

Uwe Dahlmann
,
K. Peter C. Vollhardt  ∗
Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, USA   Email: kpcv@berkeley.edu
› Author Affiliations

This work was enabled by the NSF (CHE 0907800).
Further Information

Publication History

Received: 14 December 2019

Accepted: 07 January 2020

Publication Date:
28 January 2020 (online)

 
 PDF Download Permissions and Reprints All articles of this category


Abstract

The title compounds, in which the terminal alkyne functions are adorned with -CH2OCH2CH2OCH2CH2OCH2CH3 or -p-C6H4OCH2CH2 OCH2CH2OCH3 substituents, were synthesized. The strategies for their preparation relied on prior art and involved the use of Sonogashira alkynylations of appropriate haloarenes, Stephens–Castro cyclizations of 1,2,4-trialkynyl-3-iodobenzenes, and Hay oxidative couplings of 1,2,3,4-tetralkynylbenzenes. The targets form yellow materials, exhibiting yellow-green fluorescence, and they are very soluble in polar solvents, but only sparingly so in nonpolar media. Attempts to convert them into the antikekulene frame through CpCo(CO)2-catalyzed (co)-cyclizations failed.


#

Key words

alkynes - carbon-rich compounds - cyclotrimerizations - dehydroannulenes - phenylenes

Dehydrobenzannulenes (‘benzocyclynes’) have garnered significant attention, historically because of their ring current properties, but more recently because of their potential applications in material science, such as in optical electronic devices, nanomaterials, supramolecular constructs, 2D carbon nets, liquid crystals, as monomers in topochemical and other polymerizations, and more.[1] We have reported on the recognition that some such arrays, when suitably adorned by additional ethynyl substituents, for example 2, could be related retrosynthetically to the first member of the circular phenylenes, circular [6]phenylene (‘antikekulene’) ([N] = number of benzene rings) 1, by CpCo(CO)2-catalyzed­ alkyne cyclotrimerization (Figure [1]).[2] [3] The phenylenes constitute a unique class of strained cyclohexa­trienoid hydrocarbons in which benzene rings are fused to cyclobutadienes in an alternating manner.[4] In this series, the elusive circular members are special, because the bond fixation exerted by the antiaromatic four-membered rings enforces superdelocalization of the inside and outside 4n π electronic circuits.[2] [3] [5] Unfortunately, our attempts to effect the conversion of the sensitive oligoalkyne 2a into the corresponding targets led only to decomposition. Introduction of stabilizing and solubilizing alkyl groups (as in 2b,c) was helpful in as much as single and, more slowly, double cyclization could be accomplished. However, further progress was arrested, even under high temperature conditions, eventually leading only to disintegration of materials.[2a] [3] In the present report, we describe our attempts to complete the circular frame of 1 by testing the oligoether bearing substrates 2d,e in this strategy. During the course of these investigations, compounds that allowed the construction of 4a,b became available, in turn permitting the examination of an as yet untested alternative approach to the target derivatives 3a,b by cocyclization of the former with 5a,b (Figure [1]). Oligoether substituents of the type shown have been used advantageously in synthetic and materials applications of related systems.[1`] [d] [e] [f] [g] [h] , [6] [7] In our case, we hoped that they would address specifically our concerns of robustness and solubility of the final targets as well as their precursors, as well as possibly facilitate metal-catalyzed transformations by ligation. In a more general synthetic vein, these efforts would make available an array of new synthetic building blocks of potential utility to practitioners in the field.

Zoom Image
Figure 1 Retrosynthetic disconnection of the circular [6]phenylene frames 1 and 3 to the ethynylated benzocyclynes 2 and 4, respectively

The synthesis of 2d,e relied on the respective strategies executed previously,[2a] [3] but employing the oligoether alkynes 6a [8] or 6b [9] (see experimental section and SI) as the peripheral alkyne substituent synthons. The route to 2d,e entailed in the first step the Pd-catalyzed 1,4-dialkynylation of 1,2,3,4-tetrabromobenzene[10] to 7d,e (Scheme [1]).[11]

Zoom Image
Scheme 1 Alkynylation of 1,2,3,4-tetrabromobenzene with 6a and 6b, respectively, to assemble 7d,e–9d,e; tetraalkynyl derivative 10d is generated during the alkynylation of 8d with 6a, in addition to 7d and 9d

The desired products could be obtained in moderate yields, comparable to those acquired in the construction of 2b,c,[2a] in addition to the under- and overalkynylated systems 8d,e and 9d,e, respectively. Reexposure of the former to the reaction conditions allowed for a significant improvement of the overall yield of 7 (8d → 7d, 65%; 8e → 7e, 59%; see experimental section). In the case of 8d, this process also generated small amounts of the tetrayne 10d.

Zoom Image
Scheme 2 Various monoalkynylations of 7d,e

The next task was the introduction of a single (initially protected) ethynyl group to 7, completing the composition of the basic building block that assembles 2 on cyclotrimerization (Scheme [2]). Unfortunately, this step proved to be cumbersome. For example, treatment of 7d,e with (trimethylsilyl)acetylene (1.1 equiv) at 100 °C generated the desired 11d,e in only ~20% yield, in addition to the tetralkynyl systems 12d,e and significant amounts of unreacted starting dibromide ~70%; see experimental section). The second alkynylation could not be suppressed under various reaction conditions, moreover 12 was difficult to separate from 11, and attempts to push conversion of 7d,e with excess (trimethylsilyl)acetylene and at temperatures >100 °C only increased the amounts of 12 formed. Similar problems were encountered in the assembly of 13e and 15d, respectively (Scheme [2]). Thus, while switching to (triisopropylsilyl)acetylene (performed for only 7e) served to reduce the amount of tetralkynyl product formed, conversion of dibromide remained poor (60% recovery). Turning to 2-methylbut-3-yn-2-ol (performed for only 7d) improved the yield of monoalkynylation (to 15d), but also that of 16d, with 36% of 7d remaining. Interest in alkyne 15d stemmed from the hope that it might function as a direct precursor to 2d by in situ deprotection and Pd-catalyzed cyclization, as reported for a preparation of the parent tribenzo[a,e,i]-cyclododeca­-5,11,17-triyne.[12]

Unsatisfied by this state of affairs, it was thought that a more selective monoalkynylation might be attained by exchanging one of the bromines in 7d,e with iodine. Indeed, low-temperature lithiation with BuLi, followed by exposure to I2 resulted in fairly good yields of 17d,e (Scheme [3]).[13] However, again, further Pd-catalyzed coupling with (trimethylsilyl)acetylene, while proceeding more efficiently than that of 7d,e (Scheme [2]), still gave significant amounts of doubly coupled derivatives 12d,e (Scheme [3]), detracting from the synthetic utility of the sequence.

Zoom Image
Scheme 3 Bromine–iodine exchange of 7d,e to give 17d,e and subsequent (trimethylsilyl)ethynylation to 11d,e and 12d,e

Nevertheless, with sufficient quantities of materials in hand, the next step was to convert the bromine substituent in 11d,e (and 13e) into iodine, necessary because the bromides appear to be unsuitable for the eventual cyclization to 2d,e.[14] The hope that alcohol 15d would prove to be an exception (vide supra) evaporated, when its treatment with aqueous NaOH and Pd-Cu catalysts under phase-transfer conditions[12] led to only decomposition. Therefore, as shown in Scheme [4,] 11d,e were subjected to the same sequence used for the conversion of 7d,e into 17d,e (Scheme [3]), providing the iodoarenes 18d,e, which were then deprotected to 20d,e. Similarly, 13e from Scheme [2] could be engaged to augment the supply of 20e via bromine–iodine exchange to 19e (78%), the TIPS analogue of 18e (see experimental section), and its protodesilylation employing TBAF (97%). Finally, 20d,e transformed to air stable 2d,e by Stephens–Castro coupling[2a] [15] in moderate yields (Scheme [4]). Their D 3h symmetry is evident in their relatively simple NMR spectra. Like their relatives 2a–c, they are yellow materials (2d: oil; 3e: solid), exhibiting intense yellow-green fluorescence (for the fluorescence data, see experimental section).[16] As expected, these macrocycles (as well as all of the precursors in their synthesis) are very soluble in polar solvents and only sparingly so in nonpolar media. One notes that this and prior steps do not seem the benefit from the presence of the potentially chelating oligoether appendages when compared to those featured in the routes to 2a–c.[2a]

Zoom Image
Scheme 4 Preparation of targets 2d,e through bromine–iodine exchange of 11d,e to give 18d,e, subsequent deprotection, and cyclization

The availability of the tetraalkynylarenes 12d,e and 14e (albeit as side products of the synthesis of 11d,e and 13e, respectively; Scheme [2]) suggested a ready test of the viability of the retrosynthetic analysis 3 ⇒ 4 (Figure [1]), as their deprotected versions should lead to the required benzo­cyclyne 4 by oxidative dimerization.[14b] Consequently, improved­ preparations of these materials were developed (Scheme [5]), applying excess silylalkyne for the couplings with dibromides 7d,e and furnishing good quantities of 12d (82%), 12e (78%), and 14e (57%; see experimental section). Desilylation of all proceeded nearly quantitatively on treatment with basic MeOH (Scheme [5]) or TBAF (for 14e, see experimental section) to supply 21d,e. The latter were then transformed into tetraynes 4a,b under Hay conditions,[16k] [l] [17] generating minor amounts of the only partly characterized cyclic trimers 22d,e.[2c] Compounds 4a,b exist as sensitive, shiny yellow, fluorescent crystalline materials, very soluble in polar solvents and decomposing on melting.

Zoom Image
Scheme 5 Synthesis of benzocyclynes 4a,b and 22d,e starting from dibromides 7d,e

Having accessed the benzocyclynes in Figure [1], our attention turned to their CpCo-catalyzed (co)cyclizations. We chose 2e as a first substrate, in which the phenylether substituents were expected to impart crystallinity. Disappointingly, the outcome of its exposure to excess CpCo(CO)2 mimicked those observed previously with 2b and c.[2a] Thus (Scheme [6]), the first cycloisomerization took place quite well in boiling m-xylene (bp 139 °C) to provide the angular [3]phenylene frame of 23 in 60% yield. The second step to 24 needed the much higher temperature of boiling tetraglyme (bp 275 °C) to proceed, but attempted further conversion into 1e reached an impasse from which the only escape was gradual decomposition on prolonged heating. The spectral data of 23 and 24 compare well with those of their propyl and cyclohexylmethyl analogues,[2a] in turn resting on the presence of highly diagnostic NMR and UV/Vis absorptions for the phenylene substructures.[4] [18] These findings cement the original structural rationale for the failure to effect the conversion of 2 into 1: The introduction of phenylene units causes the remaining triple bonds to be increasingly distant, posing an insurmountable barrier for the final cyclization.

Zoom Image
Scheme 6 Attempted CpCo-catalyzed cycloisomerization of 2e to 1e via 23 and 24

In view of this fiasco, further efforts along this strategy involving 2d were abandoned, and our attention turned to the potential of the 4 + 5 → 3 approach (Figure [1]), focusing first on the reaction of 4a with 5a (10 equivalents) in the presence of CpCo(CO)2 (5 equivalents) in boiling m-xylene. Lamentably, this treatment led to extensive decomposition, without the generation of any identifiable material. To test the basic reactivity of 4a in cocyclizations, the reaction was repeated with bis(trimethylsilyl)acetylene (BTMSA) in m-xylene (1:1). A complex mixture of CpCo complexes ensued, parceled into various fractions by repeated column chromatography and containing in part the known products derived from the reaction of BTMSA with CpCo(CO)2 (1H NMR), most prominently CpCo[1,2,3,4-tetrakis(trimethyl­silyl)cyclobutadiene] (18% based on CpCo(CO)2).[19] In addition, one fraction indicated the formation of a mixture of (mainly two) cyclobutadiene complexes derived from 4a and BTMSA, as evidenced by sets of four doublets (J ≈ 8 Hz) for the desymmetrized benzocyclyne frame and the corresponding CpCo and TMS singlets. Most telling was the absence of any relatively shielded 1H NMR absorptions that would be have been expected for the angular [3]phenylene substructure. Consequently, this line of enquiry was terminated.

In conclusion, we have made available new alkyne synthetic building blocks containing oligoether substituents of potential use to researchers engaged in the exploration of supramolecular assemblies. In our efforts, these were elaborated to the benzocyclynes 2d, 2e, 4a, and 4b, with the aim to test their suitability as precursors to the antikekulenes 1d, 1e, 3a, and 3b. The substituents delivered on their promise to impart excellent solubility on these compounds, but did not do so with respect to improving the efficiency of the various Pd-, Cu-, and Co-mediated transformations. In particular, the specific aim to exploit them for the assembly of the antikekulene nucleus failed.

All reactions were carried out in degassed solvents under N2 in flame-dried glassware. Unless otherwise noted, starting materials were obtained commercially and the solvents purified and dried applying common methods.[20] Et3N, TMEDA, and pyridine were freshly distilled from KOH. Et2O, DME, THF, and m-xylene were distilled from sodium benzophenone ketyl just prior to use. Chlorobenzene was dried by boiling over CaH2. Silica gel (60–200 mesh) for column chromatography was purchased from ICN-Biomedicals. TLC was performed on Merck silica gel 60 F254 (aluminum foil). Mps were determined in open Pyrex capillaries on a Thomas Hoover melting point apparatus and are uncorrected. GC was carried out on a Hewlett Packard HP 5890 Series II instrument. UV-Visible spectra were recorded with CH3CN solutions on a Hewlett Packard HP 8453 UV-Vis ChemStation. Fluorescence spectra were measured with MeCN solutions on an ISA/SPEX Fluorolog 3.22 spectrometer equipped with a 450-W Xe lamp. The samples were excited at the described wavelength, slit widths were set to 2 nm bandpass (excitation) and 3 nm bandpass (emission). IR spectra were obtained on films (NaCl) or KBr pellets with a Perkin-Elmer PE 2000 FT-IR spectral photometer. 1H NMR and 13C{H} spectra were recorded on Bruker DRX-500, AMX-400, AM-400, and AMX-300 spectrometers. When so specified, the extent of substitution on carbon was determined by APT (attached proton test) spectra. Mass data were provided by the UC Berkeley Mass Laboratory or were measured as GC-MS spectra on a Hewlett Packard HP 5970A mass detector instrument at 70 eV combined with the GC apparatus described above.


#

3-[2-(2-Ethoxyethoxy)ethoxy]prop-1-yne (6a)[8]

To a suspension of pure NaH (2.40 g, 100 mmol) in anhyd DME (100 mL) was slowly added 2-(2-ethoxyethoxy)ethanol (13.42 g, 100 mmol) at r.t. After stirring for 30 min, the now clear solution was treated with 3-bromoprop-1-yne (11.9 g, 100 mmol) in PhMe (2 mL) over a period of 15 min (violent reaction) with vigorous stirring. The resulting blend was heated to reflux for 4 h, allowed to cool to r.t., and filtered. Addition of H2O (300 mL) was followed by extraction with CH2Cl2 (3 × 100 mL), and the organic layers were combined, washed with H2O (3 × 100 mL), and dried (MgSO4). Evaporation of the solvents under reduced pressure and vacuum distillation of the residual liquid gave 6a as a colorless liquid; yield: 12.9 g (75%); bp 47–48 °C/0.1 Torr. Employment of prop-2-yn-1-yl 4-methylbenzenesulfonate in DME instead of 3-bromoprop-1-yne generated 6a in only 40% yield.

IR (film): 3251, 2975, 2868, 2114, 1444, 1349, 1289, 1246, 1107, 1033, 948, 920, 844, 671 cm–1.

1H NMR (300 MHz, CDCl3): δ = 4.19 (d, J = 2.4 Hz, 2 H), 3.68 (AA′BB′m, 4 H), 3.64 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.51 (q, J = 7.0 Hz, 2 H), 2.40 (t, J = 2.4 Hz, 1 H), 1.19 (t, J = 7.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 79.3 (CH), 74.3 (Cquat), 70.4 (CH2), 70.1 (CH2), 69.5 (CH2), 68.8 (CH2), 66.3 (CH2), 58.0 (CH2), 14.8 (CH3).

MS (EI, 70 eV): m/z (%) = 173 ([MH+], 55), 127 (10), 117 (10), 103 (20), 83 (40), 73 (100), 59 (70).

HRMS (EI, 70 eV): m/z [MH+] calcd for C9H17O3: 173.1178; found: 173.1173.


#

1-Ethynyl-4-[2-(2-methoxyethoxy)ethoxy]benzene (6b)[9]

To a suspension of pure NaH (1.20 g, 50 mmol) in anhyd DME (100 mL) was added slowly a solution of 4-iodophenol (11.0 g, 50 mmol) in anhyd DME (50 mL) at r.t. to give a clear solution after stirring for 30 min. This mixture was treated with 1-bromo-2-(2-methoxyethoxy)ethane (6.80 mL, 9.25 g, 50 mmol) in one portion with vigorous stirring, followed by boiling for 3 h, cooling to r.t., filtration, solvent evaporation under reduced pressure, and vacuum distillation to render 1-iodo-4-[2-(2-methoxyethoxy)ethoxy]benzene as a light-sensitive, colorless, glass-like solid; yield: 12.8 g (79%); mp 35–45 °C; bp 133–135 °C/0.25 Torr. The product can also be purified by column chromatography (silica gel, EtOAc/hexane 1:1).

IR (film): 2924, 2877, 2824, 1587, 1486, 1454, 1401, 1355, 1331, 1283, 1246, 1200, 1176, 1111, 1058, 1030, 1000, 940, 924, 822, 695, 636, 585 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.53 (d, J = 9.0 Hz, 2 H), 6.69 (d, J = 9.0 Hz, 2 H), 4.09 (AA′m, 2 H), 3.84 (BB′m, 2 H), 3.70 (AA′m, 2 H), 3.57 (BB′m, 2 H), 3.38 (s, 3 H).

13C NMR (125 MHz, CDCl3): δ = 158.6 (Cquat), 138.1 (CH), 117.0 (CH), 82.9 (Cquat), 71.9 (CH2), 70.7 (CH2), 69.6 (CH2), 67.5 (CH2), 59.1 (CH3).

MS (EI, 70 eV): m/z (%) = 322 ([M+], 100), 246 (10), 220 (20), 203 (55), 150 (5), 120 (15), 103 (40), 76 (15), 59 (85).

At r.t., a solution of (trimethylsilyl)acetylene (6.40 mL, 4.42 g, 45 mmol,) in Et3N (20 mL) was injected into a Fisher–Porter vessel containing 1-iodo-4-[2-(2-methoxyethoxy)ethoxy]benzene (11.9 g, 37 mmol), Cl2Pd(PPh3)2 (702 mg, 1.00 mmol), and CuI (190 mg, 1.00 mmol) in Et3N (130 mL). The bottle was sealed and the mixture stirred for 24 h at r.t., followed by 2 h at 50 °C. During this time, the solution turned bright yellow rapidly, then yellow-brown, and finally dark brown with the formation of a precipitate. After filtration, the solvent was evaporated in vacuo and the resulting residue purified by column chromatography (silica gel, hexane/EtOAc 2:1) to furnish 1-[2-(2-methoxyethoxy)ethoxy]-4-[(trimethylsilyl)ethynyl]benzene as a colorless oil; yield: 10.44 g (96%).

IR (film): 3043, 2958, 2927, 2879, 2822, 2156, 1605, 1570, 1507, 1455, 1411, 1356, 1331, 1288, 1250, 1200, 1173, 1111, 1062, 925, 866, 842, 761, 699, 638, 542 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.39 (d, J = 8.8 Hz, 2 H), 6.83 (d, J = 8.8 Hz, 2 H), 4.14 (AA′m, 2 H), 3.86 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.40 (s, 3 H), 0.23 (s, 9 H).

13C NMR (100 MHz, CDCl3): δ = 158.6 (Cquat), 133.0 (CH), 115.0 (Cquat), 114.1 (CH), 104.9 (Cquat), 92.0 (Cquat), 71.5 (CH2), 70.3 (CH2), 69.2 (CH2), 67.0 (CH2), 58.6 (CH3), –0.27 (CH3).

MS (EI, 70 eV): m/z (%) = 292 ([M+], 100), 233 (5), 175 (40), 103 (30), 89 (10), 73 (5), 59 (55).

To a solution of 1-[2-(2-methoxyethoxy)ethoxy]-4-[(trimethylsilyl)ethynyl]benzene (10.2 g, 35 mmol) in MeOH (200 mL) was added sat. aq K2CO3 (5 mL, 40 mmol) at r.t. The resulting cloudy solution was stirred until clear (approx. 1 h, TLC monitoring), diluted with CH2Cl2 (200 mL), washed with H2O (3 × 100 mL), dried (MgSO4), and the volatiles were removed under reduced pressure. The crude material was purified by column chromatography (silica gel, hexane/EtOAc 2:1) to supply 6b as a colorless oil; yield: 7.15 g (93%).

IR (film): 3285, 3072, 3042, 2926, 2879, 2824, 2106, 1606, 1571, 1505, 1455, 1355, 1289, 1249, 1200, 1172, 1110, 1061, 1030, 925, 835, 702, 659, 642 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.41 (d, J = 8.8 Hz, 2 H), 6.85 (d, J = 8.8 Hz, 2 H), 4.14 (AA′m, 2 H), 3.86 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.57 (BB′m, 2 H), 3.39 (s, 3 H), 2.99 (s, 1 H).

13C NMR (100 MHz, CDCl3): δ = 158.8 (Cquat), 133.1 (CH), 114.2 (CH), 113.9 (Cquat), 83.3 (Cquat), 75.8 (CH), 71.5 (CH2), 70.3 (CH2), 69.2 (CH2), 67.0 (CH2), 58.6 (CH3).

MS (FAB, 70 eV): m/z (%) = 221 ([MH+]).

HRMS (FAB, 70 eV): m/z [M+] calcd for C13H16O3: 221.1099; found: 221.1103.


#

2,3-Dibromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (7d)

Alkyne 6a (4.30 g, 25 mmol) in Et3N (50 mL) was injected into a Fisher­–Porter vessel containing a mixture of 1,2,3,4-tetrabromobenzene[10] (3.94 g, 10 mmol), Cl2Pd(PPh3)2 (176 mg, 0.25 mmol), and CuI (48 mg, 0.25 mmol) in Et3N (100 mL) at r.t. The mixture was stirred for 12 h at 70 °C, during which it turned rapidly bright yellow, then yellow-brown, and finally dark brown with the formation of a precipitate. The suspension was cooled to r.t., filtered, and the volatiles removed in vacuo. The resulting residue was purified by column chromatography (silica gel, Et2O) to separate first the monoalkynylated constituent 1,2,3-tribromo-4-{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (8d) as a light yellow oil; yield: 600 mg (12%).

IR (film): 3073, 2973, 2867, 2224, 1563, 1485, 1456, 1430, 1374, 1340, 1287, 1271, 1242, 1103, 1054, 1031, 976, 946, 817, 787, 722 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.50 (d, J = 8.3 Hz, 1 H), 7.24 (d, J = 8.3 Hz, 1 H), 4.45 (s, 2 H), 3.79 (AA′M, 2 H), 3.70 (BB′m, 2 H), 3.64 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.51 (q, J = 7.0 Hz, 2 H), 1.19 (t, J = 7.0 Hz, 3 H).

13C NMR (100 MHz, CDCl3): δ = 132.1, 131.7, 129.1, 128.2, 125.9, 125.8, 91.3, 84.5, 70.6, 70.3, 69.7, 69.2, 66.5, 58.9, 15.1.

MS (EI, 70 eV): m/z (%) = 486 ([M+], 2), 484 ([M+], 2), 456 (2), 454 (2), 440 (2), 438 (2), 427 (10), 425 (10), 413 (2), 411 (2), 353 (57), 351 (57), 274 (18), 272 (18), 193 (20), 191 (20), 116 (17), 73 (64), 72 (100), 59 (40).

HRMS (EI, 70 eV): m/z [M+] calcd for C15H17 79Br3O3: 481.8728; found: 481.8728.

UV/VIS (MeCN): λmax (log ε) = 224 (4.55), 257 (4.28), 269 nm (4.24).

A second fraction furnished dialkynylated product 7d as a light yellow oil; yield: 3.50 g (61%).

IR (film): 2974, 2868, 2220, 1577, 1485, 1449, 1375, 1351, 1289, 1245, 1107, 1032, 971, 945, 841, 733, 666 cm–1.

1H NMR (300 MHz, CDCl3): δ = 7.33 (s, 2 H), 4.48 (s, 4 H), 3.79 (AA′ m, 4 H), 3.71 (BB′m, 4 H), 3.66 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.51 (q, J = 7.0 Hz, 4 H), 1.20 (t, J = 7.0 Hz, 6 H).

13C NMR (100 MHz, CDCl3): δ = 131.2, 128.4, 126.5, 92.0, 84.8, 70.5, 70.3, 69.6, 69.1, 66.4, 58.9, 15.0.

MS (EI, 70 eV): m/z (%) = 576 ([M+], 2), 503 (10), 442 (19), 327 (15), 311 (26), 217 (20), 150 (28), 117 (50), 103 (75), 89 (58), 73 (100), 59 (40).

HRMS (EI, 70 eV): m/z [M+] calcd for C24H32 79Br2O6: 574.0566; found: 574.0567.

UV/VIS (MeCN): λmax (log ε) = 222 (4.34), 229 (4.35), 277 (4.39), 289 nm (4.51).

The last fraction gave rise to trialkynylated ingredient 2-bromo-1,3,4-tris{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (9d) as a yellow oil; yield: 1.20 g (18%).

IR (film): 2974, 2868, 2228, 1578, 1486, 1458, 1385, 1349, 1292, 1267, 1246, 1209, 1099, 1056, 1030, 977, 947, 843, 763, 669 cm–1.

1H NMR (300 MHz, CDCl3): δ = 7.31 (s, 2 H), 4.50 (s, 2 H), 4.47 (s, 2 H), 4.45 (s, 2 H), 3.85–3.75 (m, 6 H), 3.72–3.69 (m, 6 H), 3.67–3.63 (m, 6 H), 3.61–3.56 (m, 6 H), 3.52 (q, J = 7.0 Hz, 2 H), 3.51 (q, J = 7.0 Hz, 4 H), 1.19 (t, J = 7.0 Hz, 9 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 131.8, 130.2, 128.3, 127.6, 126.4, 125.3, 94.3, 91.6, 91.4, 84.3, 84.0, 83.5, 70.5 (3 C), 70.2 (3 C), 69.6 (3 C), 69.1, 69.0, 68.9, 66.4 (3 C), 58.8 (br, 3 C), 14.9 (3 C).

MS (EI, 70 eV): m/z (%) = 534 ([M+], 4), 532 ([M+], 4), 461 (1), 459 (1), 117 (20), 73 (55), 59 (100).

MS (FAB, 70 eV): m/z (%) = 669 ([MH+]), 667 ([MH+]).

HRMS (FAB, 70 eV): m/z [MH+] calcd for C33H48 81BrO9: 669.2461); found: 669.2457.

UV/VIS (MeCN): λmax (log ε) = 247 (4.60), 254 (4.67), 277 (4.33), 283 (4.36), 294 nm (4.49).


#

2,3-Dibromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (7d) by Alkynylation of 8d

Monoalkynylated 8d (4.85 g, 10 mmol) was exposed to 6a (3.80 g, 22 mmol) as in the preceding preparation of 7d, except that the reaction temperature was kept at 100 °C, to engender, in order of elution on chromatography, 7d; yield: 4.37 g (65%); 9d; yield: 1.27 g (19%); and the tetraalkynylated product 1,2,3,4-tetrakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}benzene (10d) as a yellow oil; yield: 610 mg (8%).

IR (film): 2974, 2868, 2227, 1486, 1462, 1408, 1349, 1297, 1245, 1106, 1049, 1029, 947, 845 cm–1.

1H NMR (300 MHz, CDCl3): δ = 7.30 (s, 2 H), 4.48 (s, 4 H), 4.44 (s, 4 H), 3.81–3.75 (m, 8 H), 3.69–3.62 (m, 16 H), 3.61–3.57 (m, 8 H), 3.51 (q, J = 7.1 Hz, 4 H), 3.50 (q, J = 7.1 Hz, 4 H), 1.191 (t, J = 7.1 Hz, 6 H), 1.187 (t, J = 7.1 Hz, 6 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 131.1, 127.7, 125.3, 93.5, 90.9, 84.1, 83.2, 70.54, 70.53, 70.3 (2 C), 69.6 (2 C), 69.0, 68.8, 66.4 (2 C), 58.92, 58.89, 15.0 (2 C).

MS (EI, 70 eV): m/z (%) = 758 ([M+], 0.2), 624 (3), 552 (25), 117 (45), 103 (20), 73 (75), 59 (100).

UV/VIS (MeCN): λmax (log ε) = 254 (sh, 4.60), 256 (sh, 4.65), 263 (4.77), 277 (4.47), 285 (4.28), 296 nm (4.47).


#

2,3-Dibromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (7e)

Following the procedure employed for the preparation of 7d, treatment of 1,2,3,4-tetrabromobenzene[10] (3.94 g, 10 mmol) with alkyne 6b (4.88 g, 22 mmol) and column chromatography (silica gel, EtOAc) produced a first fraction containing 1,2,3-tribromo-4-({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (8e) as colorless crystals; yield: 1.35 g (25%); mp 84 °C (EtOH).

IR (KBr): 2985, 2951, 2925, 2889, 2856, 2816, 2224, 1605, 1561, 1509, 1456, 1429, 1384, 1363, 1340, 1283, 1250, 1167, 1140, 1114, 1085, 1058, 1021, 936, 916, 848, 823, 724, 562, 532 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.54 (d, J = 8.4 Hz, 1 H), 7.49 (d, J = 8.8 Hz, 2 H), 7.32 (d, J = 8.4 Hz, 1 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.17 (AA′m, 2 H), 3.87 (BB′m, 2 H), 3.72 (AA′m, 2 H), 3.58 (BB′m, 2 H), 3.40 (s, 3 H).

13C NMR (100 MHz, CDCl3): δ = 159.4, 133.2, 131.8, 131.6, 128.9, 128.2, 126.9, 125.1, 114.7, 114.5, 95.5, 86.9, 71.9, 70.7, 69.6, 67.4, 59.0.

MS (EI, 70 eV): m/z (%) = 534 ([M+], 65), 532 ([M+], 65), 432 (16), 430 (16), 243 (6), 241 (6), 174 (8), 103 (30), 59 (100).

HRMS (EI, 70 eV): m/z [M+] calcd for C19H17 81Br3O3: 535.8667; found: 535.8667.

UV/VIS (MeCN): λmax (log ε) = 218 (4.32), 244 (4.00), 254 (3.93), 272 (3.89), 309 (4.37), 324 nm (4.38).

The second fraction consisted of 7e as colorless flakes; yield: 3.86 g (57%); mp 96–97 °C (EtOH).

IR (KBr): 3070, 3041, 2988, 2875, 2824, 2226, 2212, 1602, 1571, 1542, 1516, 1473, 1458, 1383, 1351, 1332, 1303, 1286, 1251, 1197, 1167, 1145, 1123, 1101, 1062, 1030, 955, 925, 911, 885, 855, 844, 828, 811, 789, 708, 644, 627, 537 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.50 (d, J = 8.9 Hz, 4 H), 7.42 (s, 2 H), 6.91 (d, J = 8.9 Hz, 4 H), 4.17 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.58 (BB′m, 4 H), 3.40 (s, 6 H).

13C NMR (100 MHz, CDCl3): δ = 159.2, 133.1, 130.6, 128.1, 126.7, 114.6, 114.5, 96.0, 87.4, 71.7, 70.6, 69.4, 67.3, 58.9.

MS (EI, 70 eV): m/z (%) = 672 ([M+], 100), 569 (5), 103 (15), 59 (60).

HRMS (EI, 70 eV): m/z [M+] calcd for C32H32 79Br81BrO6: 672.0545; found: 672.0543.

UV/VIS (MeCN): λmax (log ε) = 215 (sh, 4.61), 239 (4.50), 248 (4.49), 345 (4.82), 361 nm (sh, 4.76).

A third fraction was comprised of 3-bromo-1,2,4-tris({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (9e) as light yellow waxy crystals; yield: 820 mg (10%); mp 40–50 °C (EtOH).

IR (KBr): 2928, 2877, 2824, 2215, 1604, 1571, 1514, 1456, 1357, 1287, 1250, 1200, 1166, 1111, 1059, 924, 829, 647, 612, 535 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.54 (d, J = 9.2 Hz, 2 H), 7.51 (d, J = 9.2 Hz, 2 H), 7.47 (d, J = 9.2 Hz, 2 H), 7.42 (ABq, J = 8.2 Hz, 2 H), 6.905 (d, J = 8.8 Hz, 2 H), 6.897 (d, J = 8.8 Hz, 2 H), 6.885 (d, J = 9.2 Hz, 2 H), 4.16 (m, 6 H), 3.87 (m, 6 H), 3.73 (m, 6 H), 3.58 (m, 6 H), 3.395 (s, 3 H), 3.393 (s, 6 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.22, 159.19, 159.15, 133.13, 133.12, 133.08, 130.9, 129.7, 128.3, 127.8, 126.4, 125.6, 115.1, 115.0, 114.8, 114.63, 114.61 (2 C), 98.4, 95.8, 95.6, 87.2, 86.9, 86.5, 71.8 (3 C), 70.6 (3 C), 69.5 (3 C), 67.4 (3 C), 59.0 (3 C).

MS (EI, 70 eV): m/z (%) = 812 ([M+], 10), 810 ([M+], 10), 594 (30), 592 (30), 277 (50), 107 (30), 95 (75), 59 (100).

UV/VIS (MeCN): λmax (log ε) = 228 (4.51), 234 (sh, 4.50), 286 (sh, 4.48), 322 (4.79), 343 (sh, 4.66), 361 nm (sh, 4.61).

Compound 7e could also be made by alkynylation of 8e following the protocol used for the conversion of 8d to give 7d, 9d, and 10d (vide supra) to afford 7e (59%) and 9e (21%), but no 10e.


#

2-Bromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-[(trimethylsilyl)ethynyl]benzene (11d)

(Trimethylsilyl)acetylene (0.75 mL, 520 mg, 5.30 mmol) in Et3N (10 mL) was injected into a Fisher–Porter vessel containing 7d (2.88 g, 5.00 mmol), Cl2Pd(PPh3)2 (176 mg, 0.25 mmol), and CuI (48 mg, 0.25 mmol) in Et3N (100 mL) at r.t. The vessel was sealed and the mixture heated at 100 °C for 12 h. Column chromatography (silica gel, Et2O), supplied a first fraction containing 1,4-bis{3-[2-(2-ethoxy­ethoxy)ethoxy]prop-1-yn-1-yl}-2,3-bis[(trimethylsilyl)ethynyl]benzene (12d) as a yellow oil; yield: 300 mg (10%).

IR (film): 2960, 2868, 2157, 1486, 1460, 1394, 1376, 1349, 1287, 1250, 1178, 1101, 1034, 885, 842, 761, 713, 699, 626 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.28 (s, 2 H), 4.46 (s, 4 H), 3.78 (AA′m, 4 H), 3.70 (BB′m, 4 H), 3.65 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.51 (q, J = 7.0 Hz, 4 H), 1.19 (t, 3 J = 7.0 Hz, 6 H), 0.25 (s, 18 H).

13C NMR (100 MHz, CDCl3): δ = 131.0, 128.4, 125.5, 103.6, 101.2, 90.8, 84.2, 70.6, 70.4, 69.7, 69.1, 66.5, 59.0, 15.1, –0.14.

MS (EI, 70 eV): m/z (%) = 610 ([M+], 5), 537 (10), 493 (20), 476 (40), 147 (8), 117 (40), 103 (8), 73 (100), 59 (15).

HRMS (EI, 70 eV): m/z [M+] calcd for C34H50O6Si2: 610.3146; found: 610.3160.

UV/VIS (MeCN): λmax (log ε) = 257 (sh, 4.48), 262 (sh, 4.73), 269 (4.90), 282 (4.64), 287 (sh, 4.55), 298 nm (4.46).

The second fraction delivered 11d as a yellow oil; yield: 560 mg (19%).

IR (film): 2973, 2867, 2223, 2158, 1577, 1486, 1456, 1377, 1349, 1290, 1250, 1192, 1109, 1035, 977, 945, 883, 847, 760, 701, 684, 663, 624 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.30 (ABq, 2 H), 4.45 (s, 4 H), 3.77 (m, 4 H), 3.71 (m, 4 H), 3.65 (m, 4 H), 3.59 (m, 4 H), 3.53 (q, J = 7.0 Hz, 2 H), 3.51 (q, J = 7.0 Hz, 2 H), 1.195 (t, J = 7.0 Hz, 3 H), 1.191 (t, J = 7.0 Hz, 3 H), 0.26 (s, 9 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 31.9, 130.3, 128.6, 128.2, 126.7, 125.4, 104.7, 101.4, 91.6, 91.5, 84.6, 84.1, 70.65, 70.62, 70.4 (2 C), 69.7 (2 C), 69.2 (2 C), 66.6 (2 C), 59.01, 58.98, 15.1, –0.26.

MS (EI, 70 eV): m/z (%) = 594 ([M+], 2), 592 ([M+], 2), 535 (2), 533 (2), 521 (5), 519 (5), 491 (2), 489 (2), 477 (15), 475 (15), 460 (20), 458 (20), 117 (60), 73 (100), 59 (25).

HRMS (EI, 70 eV): m/z [M+] calcd for C29H41 79BrO6Si: 592.1856; found: 592.1851.

UV/VIS (MeCN): λmax (log ε) = 241 (sh, 4.42), 246 (sh, 4.56), 250 (4.59), 258 (4.77), 279 (4.32), 286 (4.35), 296 nm (4.44).

A third fraction returned starting material 7d; yield: 1.50 g (66%).


#

3-Bromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2-[(trimethylsilyl)ethynyl]benzene (11e)

The procedure for the preparation of 11d was replicated, but starting with 7e (3.36 g, 5 mmol). Column chromatography (silica gel, Et2O) furnished a first fraction containing 1,4-bis({4-[2-(2-methoxy­ethoxy)ethoxy]phenyl}ethynyl)-2,3-bis[(trimethylsilyl)ethynyl]benzene (12e) as light yellow needles; yield: 100 mg (3%); mp 100–101 °C dec (MeOH).

IR (KBr): 2959, 2874, 2826, 2210, 1602, 1510, 1458, 1392, 1355, 1283, 1250, 1198, 1166, 1144, 1123, 1110, 1059, 1030, 1013, 954, 940, 922, 846, 811, 762, 677, 618, 541 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.47 (d, J = 8.8 Hz, 4 H), 7.37 (s, 2 H), 6.89 (d, J = 8.8 Hz, 4 H), 4.16 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.72 (AA′m, 4 H), 3.58 (BB′m, 4 H), 3.39 (s, 6 H), 0.29 (s, 18 H).

13C NMR (100 MHz, CDCl3): δ = 159.1, 133.2, 130.6, 128.1, 125.9, 115.3, 114.6, 103.9, 101.6, 95.2, 86.8, 71.9, 70.8, 69.6, 67.5, 59.1, 0.06.

MS (EI, 70 eV): m/z (%) = 706 ([M+], 100), 603 (10), 59 (15).

HRMS (EI, 70 eV): m/z [M+] calcd for C42H50O6Si2: 706.3146; found: 706.3160.

UV/VIS (MeCN): λmax (log ε) = 263 (sh, 4.56), 273 (4.62), 287 (4.66), 348 (4.70), 361 nm (sh, 4.66).

The second fraction revealed 11e as colorless needles; yield: 710 mg (21%); mp 66–67 °C (MeOH).

IR (KBr): 3073, 2929, 2874, 2825, 2217, 1603, 1522, 1509, 1457, 1380, 1354, 1289, 1251, 1166, 1145, 1125, 1111, 1060, 1030, 974, 955, 923, 845, 761, 671, 619, 536 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.50 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8 Hz, 2 H), 7.39 (br s, 2 H), 6.91 (AA′m, 2 H), 6.89 (BB′m, 2 H), 4.17 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.58 (BB′m, 4 H), 3.40 (br s, 6 H), 0.30 (s, 9 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.23, 159.18, 133.2 (2 C), 131.5, 129.2, 128.4, 127.7, 127.0, 125.6, 115.0, 114.8, 114.64, 114.59, 104.3, 101.8, 95.8, 95.6, 87.1, 86.7, 71.8 (2 C), 70.7 (2 C), 69.6 (2 C), 67.4 (2 C), 59.0 (2 C), –0.17.

MS (EI, 70 eV): m/z (%) = 690 ([M+], 50), 688 ([M+], 50), 587 (20), 585 (20), 103 (30), 59 (100).

HRMS (EI, 70 eV): m/z [M+] calcd for C37H41 81BrO6Si: 690.1850; found: 690.1855.

UV/VIS (MeCN): λmax (log ε) = 251 (4.58), 275 (4.60), 343 (4.75), 353 nm (sh, 4.73).

The third fraction led to recovered starting material 7e; yield: 2.46 g (73%).


#

3-Bromo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2-[(triisopropylsilyl)ethynyl]benzene (13e)

(Triisopropylsilyl)acetylene (1.23 mL, 1.00 g, 5.48 mmol) was reacted with 7e (3.36 g, 5.00 mmol) following the experimental procedure for the preparation of 7d. Column chromatography (silica gel, EtOAc) led first to 1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2,3-bis[(triisopropylsilyl)ethynyl]benzene (14e) as light yellow needles; yield: 48 mg (1%); mp 65–66 °C (EtOH).

IR (KBr): 2942, 2889, 2865, 2214, 2134, 1604, 1510, 1457, 1392, 1353, 1286, 1248, 1200, 1169, 1142, 1127, 1110, 1061, 999, 951, 936, 923, 883, 836, 754, 679, 612, 592, 541 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.43 (d, J = 8.8 Hz, 4 H), 7.40 (s, 2 H), 6.87 (d, J = 8.8 Hz, 4 H), 4.17 (AA′m, 4 H), 3.88 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.40 (s, 6 H), 1.10 (m, 42 H).

13C NMR (100 MHz, CDCl3): δ = 159.0, 133.1, 131.5, 127.6, 127.0, 115.4, 114.4, 103.3, 100.3, 94.8, 86.9, 71.9, 70.7, 69.6, 67.4, 59.0, 18.7, 11.4.

MS (FAB, 70 eV): m/z (%) = 875 ([MH+]).

UV/VIS (MeCN): λmax (log ε) = 266 (sh, 4.60), 275 (4.68), 290 (4.71), 345 nm (4.59).

Next to be eluted was 13e, forming colorless crystals; yield: 1.07 g (28%); mp 108 °C dec (EtOH).

IR (KBr): 3061, 2941, 2865, 2220, 1602, 1510, 1455, 1378, 1357, 1287, 1246, 1233, 1203, 1170, 1140, 1111, 1060, 1018, 970, 950, 922, 882, 842, 830, 811, 680, 648, 604, 538, 509 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.50 (d, J = 8.8 Hz, 2 H), 7.44 (d, J = 8.8 Hz, 2 H), 7.40 (ABq, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 6.88 (d, J = 8.8 Hz, 2 H), 4.17 (AA′m, 4 H), 3.88 (BB′m, 4 H), 3.73 (AA′m, 4 H), 3.59 (BB′m, 4 H), 3.40 (s, 6 H), 1.15 (m, 21 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.3, 159.1, 133.20, 133.14, 131.2, 130.3, 129.0, 127.9, 127.0, 125.7, 115.1, 114.9, 114.7, 114.5, 103.5, 101.3, 95.6, 95.5, 87.2, 86.7, 71.9 (2 C), 70.7 (2 C), 69.59, 69.57, 67.4 (2 C), 59.0 (2 C), 18.7, 11.3.

MS (EI, 70 eV): m/z (%) = 774 ([M+], 60), 772 ([M+], 60), 262 (100), 183 (46), 59 (50).

UV/VIS (MeCN): λmax (log ε) = 252 (4.53), 277 (4.54), 343 (4.68), 359 nm (sh, 4.61).

A last fraction contained recovered 7e; yield: 2.02 g (60%).


#

4-(2-Bromo-3,6-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}phenyl)-2-methylbut-3-yn-2-ol (15d)

2-Methylbut-3-yn-2-ol (750 μL, 650 mg, 7.70 mmol) was reacted with 7d (1.73 g, 3.00 mmol), following the experimental procedure for the preparation of 7d. Column chromatography (silica gel, Et2O) separated first starting material 7d; yield: 674 mg (39%); followed by 15d as a yellow oil; yield: 633 mg (36%).

IR (film): 3427, 2977, 2924, 2869, 2228, 1579, 1485, 1456, 1372, 1349, 1291, 1268, 1243, 1154, 1105, 1029, 963, 917, 840, 789, 748, 708, 666 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.30 (ABq, 2 H), 4.48 (br s, 4 H), 3.81 (AA′m, 4 H), 3.72 (BB′m, 4 H), 3.67 (AA′m, 4 H), 3.60 (BB′m, 4 H), 3.531 (q, J = 7.0 Hz, 2 H), 3.524 (q, J = 7.0 Hz, 2 H), 1.64 (s, 6 H), 1.208 (t, J = 7.0 Hz, 3 H), 1.202 (t, J = 7.0 Hz, 3 H).

13C NMR (125 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 131.6 (CH), 129.7 (CH), 128.1 (Cquat), 128.0 (Cquat), 126.3 (Cquat), 125.2 (Cquat), 103.5 (Cquat), 91.5 (Cquat), 91.3 (Cquat), 84.4 (Cquat), 84.2 (Cquat), 79.4 (Cquat), 70.5 (CH2, 2 C), 70.2 (CH2, 2 C), 69.57 (CH2), 69.49 (CH2), 69.12 (CH2), 69.04 (CH2), 66.4 (CH2, 2 C), 65.1 (Cquat), 58.99 (CH2), 58.85 (CH2), 31.1 (CH3), 14.97 (CH3), 14.94 (CH3).

MS (EI, 70 eV): m/z (%) = 580 ([M+], 0.2), 578 ([M+], 0.2), 562 (30), 560 (30), 489 (10), 487 (10), 428 (20), 426 (20), 189 (44), 117 (70), 73 (100), 59 (60).

UV/VIS (MeCN): λmax (log ε) = 248 (4.61), 255 (4.69), 277 (4.34), 284 (4.37), 294 nm (4.49).

Eluting the column with EtOAc gave 4,4′-(3,6-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-1,2-phenylene)bis(2-methylbut-3-yn-2-ol) (16d) as a yellow oil; yield: 160 mg (9%).

IR (film): 3416, 2978, 2930, 2868, 2227, 1461, 1407, 1350, 1294, 1252, 1224, 1170, 1104, 1036, 963, 919, 841, 769, 741, 673 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.27 (s, 2 H), 4.47 (s, 4 H), 3.81 (AA′m, 4 H), 3.72 (BB′m, 4 H), 3.66 (AA′m, 4 H), 3.60 (BB′m, 4 H), 3.52 (q, J = 7.0 Hz, 4 H), 2.51 (v br s, 2 H), 1.63 (s, 12 H), 1.20 (t, J = 7.0 Hz, 6 H).

13C NMR (125 MHz, CDCl3): δ = 130.4 (CH), 128.1 (Cquat), 124.9 (Cquat), 102.8 (Cquat), 90.6 (Cquat), 84.4 (Cquat), 79.1 (Cquat), 70.6 (CH2), 70.3 (CH2), 69.6 (CH2), 69.1 (CH2), 66.5 (CH2), 65.3 (Cquat), 59.1 (CH2), 31.3 (CH3), 15.0 (CH3).

MS (EI, 70 eV): m/z (%) = 564 ([M+ – H2O], 40), 491 (10), 297 (22), 283 (18), 281 (17), 269 (18), 253 (28), 239 (48), 226 (34), 215 (24), 213 (18), 202 (18), 189 (14), 117 (40), 103 (10), 73 (70), 59 (100).

UV/VIS (MeCN): λmax (log ε) = 253 (sh, 4.58), 256 (sh, 4.63), 263 (4.79), 277 (4.47), 285 (4.27), 296 nm (4.45).


#

2-Bromo-1,4-bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-iodobenzene (17d)

To 7d (1.44 g, 2.50 mmol) in anhyd Et2O (100 mL) was added 1.6 M BuLi in hexane (1.9 mL, 3.0 mmol) at –110 °C. After stirring for 1 h, I2 (950 mg, 3.74 mmol) in anhyd Et2O (50 mL) was dripped in via cannula. The mixture was stirred for an additional 30 min at –110 °C and then allowed to warm to r.t. The resulting solution was washed first with sat. aq Na2S2O3, then H2O, and dried (MgSO4). The volatiles were removed in vacuo and the residue subjected to column chromatography (silica gel, Et2O) to render 17d as a light yellow oil; yield: 1.00 g (64%).

IR (film): 2973, 2868, 2218, 1573, 1485, 1442, 1375, 1347, 1288, 1263, 1246, 1104, 1031, 967, 947, 840, 801, 723, 658 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.36 (d, J = 8.0 Hz, 1 H), 7.28 (d, J = 8.0 Hz, 1 H), 4.49 (s, 2 H), 4.48 (s, 2 H), 3.84–3.77 (m, 4 H), 3.75–3.69 (m, 4 H), 3.69–3.63 (m, 4 H), 3.63–3.57 (m, 4 H), 3.52 (q, J = 7.0 Hz, 4 H), 1.20 (t, J = 7.0 Hz, 6 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 133.2, 132.2, 131.6, 130.4, 125.3, 108.6, 91.6, 91.1, 88.8, 85.4, 70.6 (2 C), 70.3 (2 C), 69.7 (2 C), 69.3, 69.2, 66.5 (2 C), 58.9 (2 C), 15.1 (2 C).

MS (EI, 70 eV): m/z (%) = 624 ([M+], 5), 622 ([M+], 5), 551 (5), 549 (5), 490 (20), 488 (20), 117 (60), 73 (100), 59 (35).

HRMS (EI, 70 eV): m/z [M+] calcd for C24H32 79BrIO6: 622.0444; found: 622.0440.

UV/VIS (MeCN): λmax (log ε) = 224 (4.32), 237 (4.31), 272 (sh, 4.33), 278 (sh, 4.36), 281 (4.42), 292 nm (4.40).


#

2-Bromo-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (17e)

Dibromide 7e (1.68 g, 2.50 mmol) was subjected to the protocol for the synthesis of 17d. Column chromatography (silica gel, EtOAc) begot 17e as colorless crystals; yield: 1.52 g (85%); mp 102–103 °C (EtOH).

IR (KBr): 3068, 2986, 2875, 2823, 2221, 1602, 1570, 1516, 1491, 1471, 1457, 1450, 1382, 1364, 1353, 1342, 1331, 1303, 1280, 1250, 1196, 1166, 1145, 1123, 1101, 1061, 1028, 1006, 955, 936, 924, 903, 887, 855, 842, 827, 812, 787, 706, 644, 626, 536 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.51 (d, J = 8.8 Hz, 2 H), 7.48 (d, J = 8.8 Hz, 2 H), 7.45 (d, J = 8.0 Hz, 1 H), 7.37 (d, J = 8.0 Hz, 1 H), 6.91 (d, J = 8.8 Hz, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.16 (m, 4 H), 3.87 (m, 4 H), 3.72 (m, 4 H), 3.58 (m, 4 H), 3.39 (s, 6 H).

1H NMR (400 MHz, C6D6): δ = 7.53 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8 Hz, 2 H), 7.09 (d, J = 8.0 Hz, 1 H), 7.02 (d, J = 8.0 Hz, 1 H), 6.72 (d, J = 8.8 Hz, 2 H), 6.68 (d, J = 8.8 Hz, 2 H), 3.68 (m, 4 H), 3.51 (m, 4 H), 3.45 (m, 4 H), 3.33 (m, 4 H), 3.12 (s, 6 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.34, 159.31, 133.15, 133.04, 132.9, 131.7, 131.6, 129.7, 125.5, 114.67 (2 C), 114.65 (2 C), 108.7, 95.7, 95.1, 91.8, 88.1, 71.8 (2 C), 70.7 (2 C), 69.5 (2 C), 67.4 (2 C), 59.0 (2 C).

MS (EI, 70 eV): m/z (%) = 720 ([M+], 80), 718 ([M+], 80), 640 (5), 594 (20), 592 (20), 128 (10), 103 (20), 59 (100).

UV/VIS (MeCN): λmax (log ε) = 222 (4.63), 241 (4.60), 346 (4.86), 363 nm (sh, 4.80).


#

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-2-iodo-3-[(trimethylsilyl)ethynyl]benzene (18d)

To 11d (1.48 g, 2.50 mmol) in anhyd THF (100 mL) at –110 °C was added 1.6 M BuLi in hexane (1.9 mL, 3.0 mmol). After stirring for 1 h, I2 (950 mg, 3.74 mmol) in anhyd THF (50 mL) was added dropwise via cannula. The mixture was stirred for an additional 30 min at –110 °C and then allowed to warm to r.t. The resulting solution was washed first with sat. aq Na2S2O3, then H2O, and dried (MgSO4). The volatiles were removed in vacuo and the residue subjected to column chromatography (silica gel, Et2O) to give 18d as a light yellow oil; yield: 760 mg (47%).

IR (film): 2972, 2868, 2156, 1572, 1519, 1485, 1447, 1349, 1289, 1250, 1116, 1033, 971, 945, 882, 845, 761, 701, 681, 661, 623 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.33 (d, J = 8.0 Hz, 1 H), 7.24 (d, J = 8.0 Hz, 1 H), 4.48 (s, 2 H), 4.47 (s, 2 H), 3.83 (m, 2 H), 3.77 (m, 2 H), 3.74–3.68 (m, 4 H), 3.68–3.63 (m, 4 H), 3.62–3.57 (m, 4 H), 3.518 (q, J = 7.0 Hz, 2 H), 3.513 (q, J = 7.0 Hz, 2 H), 1.199 (t, J = 7.0 Hz, 3 H), 1.194 (t, J = 7.0 Hz, 3 H), 0.27 (s, 9 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 132.7, 131.18, 131.14, 130.2, 125.6, 107.4, 105.3, 103.8, 91.3, 90.8, 88.3, 84.4, 70.65 (2 C), 70.63, 70.4, 69.74, 69.73, 69.29, 69.15, 66.6 (2 C), 59.01, 58.98, 15.11, 15.09, –0.30.

MS (EI, 70 eV): m/z (%) = 640 ([M+], 30), 567 (10), 523 (10), 506 (25), 389 (10), 375 (117 (40), 103 (10), 73 (100), 59 (30).

HRMS (EI, 70 eV): m/z [M+] calcd for C29H41IO6Si: 640.1717; found: 640.1725.

UV/VIS (MeCN): λmax (log ε) = 243 (sh, 4.41), 256 (sh, 4.57), 262 (4.63), 279 (4.32), 287 (4.29), 298 nm (4.35).


#

3-Iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2-[(trimethylsilyl)ethynyl]benzene (18e)

Compound 11e (1.73 g, 2.50 mmol) was reacted according to the procedure described for the synthesis of 18d from 11d. Column chromatography (silica gel, EtOAc) furnished 18e as colorless needles; yield: 1.48 g (80%); mp 74–76 °C (MeOH).

IR (KBr): 2927, 2873, 2823, 2214, 2155, 1602, 1568, 1522, 1507, 1467, 1456, 1414, 1370, 1353, 1302, 1287, 1250, 1201, 1165, 1144, 1125, 1110, 1059, 1029, 968, 954, 936, 923, 843, 812, 761, 703, 671, 646, 618, 536 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.52 (d, J = 8.8 Hz, 2 H), 7.47 (d, J = 8.8 Hz, 2 H), 7.41 (d, J = 8.0 Hz, 1 H), 7.34 (d, J = 8.0 Hz, 1 H), 6.91 (d, J = 8.8 Hz, 2 H), 6.90 (d, J = 8.8 Hz, 2 H), 4.17 (m, 4 H), 3.88 (m, 4 H), 3.73 (m, 4 H), 3.58 (m, 4 H), 3.40 (s, 6 H), 0.31 (s, 9 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.26, 159.19, 133.15, 133.05, 132.3, 130.59, 130.54, 130.4, 125.9, 115.1, 114.9, 114.69, 114.62, 107.5, 105.8, 103.4, 95.7, 94.7, 91.2, 87.0, 71.9 (2 C), 70.7 (2 C), 69.6 (2 C), 67.4 (2 C), 59.0 (2 C), –0.21.

MS (EI, 70 eV): m/z (%) = 736 ([M+], 90), 610 (100), 633 (5), 103 (10), 59 (60+).

UV/VIS (MeCN): λmax (log ε) = 236 (sh, 4.38), 258 (4.49), 273 (sh, 4.47), 345 (4.74), 361 nm (sh, 4.69).


#

3-Iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)-2-[(triisopropylsilyl)ethynyl]benzene (19e)

Bromoarene 13e (1.945 g, 2.50 mmol) was transformed following the procedure described for the synthesis of 18d from 11d. Column chromatography (silica gel, EtOAc) produced 19e as light yellow needles; yield: 1.595 g (78%); mp 103–104 °C (EtOH).

IR (KBr): 2941, 2925, 2885, 2864, 2217, 2146, 1602, 1567, 1519, 1509, 1453, 1358, 1308, 1286, 1246, 1202, 1168, 1138, 1111, 1060, 1018, 996, 966, 950, 921, 883, 842, 831, 810, 770, 680, 647, 604, 537, 508 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.52 (d, J = 8.8 Hz, 2 H), 7.44 (d, J = 8.0 Hz, 1 H), 7.43 (d, J = 8.8 Hz, 2 H), 7.34 (d, J = 8.0 Hz, 1 H), 6.91 (d, J = 8.8 Hz, 2 H), 6.88 (d, J = 8.8 Hz, 2 H), 4.17 (m, 4 H), 3.87 (m, 4 H), 3.73 (m, 4 H), 3.59 (m, 4 H), 3.40 (s, 6 H), 1.15 (m, 21 H).

13C NMR (100 MHz, CDCl3, number of accidentally isochronous peaks based on relative peak heights or widths): δ = 159.2, 159.1, 133.2, 133.0, 132.2, 131.3, 131.0, 130.3, 126.1, 115.1, 115.0, 114.7, 114.4, 107.9, 107.1, 100.4, 95.3, 94.7, 91.2, 86.9, 71.9 (2 C), 70.7 (2 C), 69.58, 69.55, 67.4 (2 C), 59.0 (2 C), 18.7, 11.3.

MS (EI, 70 eV): m/z (%) = 820 ([M+], 100), 694 (40), 103 (5), 59 (30).

HRMS (EI, 70 eV): m/z [M+] calcd for C43H53IO6Si: 820.2656; found: 820.2671.

UV/VIS (MeCN): λmax (log ε) = 258 (4.63), 280 (4.61), 344 (4.76), 360 nm (sh, 4.68).


#

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-3-ethynyl-2-iodobenzene (20d)

To 18d (1.28 g, 2.00 mmol) in MeOH (100 mL) was added sat. aq K2CO3­ (1 mL, 8 mmol) at r.t. The resulting cloudy solution was stirred at r.t. until clear (30 min), diluted with CH2Cl2 (200 mL), washed with H2O (3 × 100 mL), dried (MgSO4), and the volatiles were removed under reduced pressure. Column chromatography (silica gel, Et2O) resulted in 20d as a heat- and light-sensitive, light yellow oil; yield: 1.12 g (99%).

IR (film): 3235, 2973, 2868, 2104, 1573, 1519, 1485, 1448, 1349, 1287, 1266, 1247, 1115, 1033, 971, 946, 839, 763, 748, 693, 670, 623 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.29 (d, J = 8.1 Hz, 1 H), 7.23 (d, J = 8.1 Hz, 1 H), 4.42 (s, 2 H), 4.41 (s, 2 H), 3.75 (m, 4 H), 3.69 (s, 1 H), 3.65 (m, 4 H), 3.60 (m, 4 H), 3.53 (m, 4 H), 3.45 (q, J = 7.0 Hz, 4 H), 1.139 (t, J = 7.0 Hz, 3 H), 1.135 (t, J = 7.0 Hz, 3 H).

13C NMR (125 MHz, CDCl3): δ = 131.7, 131.4, 131.0, 130.2, 126.1, 106.9, 91.5, 90.9, 88.1, 85.7, 84.12, 84.08, 70.49, 70.48, 70.24, 70.20, 69.60, 69.59, 69.2, 68.9, 66.41, 66.40, 58.84, 58.82, 14.98, 14.96.

MS (EI, 70 eV): m/z (%) = 568 ([M+], 2), 495 (1), 434 (3), 377 (1), 277 (100), 262 (10), 209 (7), 201 (15), 199 (15), 183 (16), 149 (16), 117 (17), 103 (10), 73 (55), 59 (50).

HRMS (EI, 70 eV): m/z [M+] calcd for C26H33IO6: 568.1322; found: 568.1332.

UV/VIS (MeCN): λmax (log ε) = 254 (4.50), 277 (4.30), 283 (4.31), 294 nm (4.43).


#

2-Ethynyl-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (20e) from 18e

Compound 18e (1.47 g, 2.00 mmol) was converted according to the procedure described for the synthesis of 20d from 18d. Column chromatography (silica gel, EtOAc) presented 20e as light yellow needles; yield: 1.27 g (96%); mp 88–90 °C (EtOH).

IR (KBr): 3246, 2940, 2927, 2878, 2828, 2809, 2216, 1602, 1569, 1519, 1508, 1490, 1471, 1456, 1356, 1333, 1303, 1287, 1249, 1195, 1168, 1139, 1121, 1098, 1062, 1030, 951, 937, 923, 852, 840, 827, 811, 792, 650, 614, 544, 534 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.51 (d, J = 8.8 Hz, 2 H), 7.46 (d, J = 8.8 Hz, 2 H), 7.43 (d, J = 8.0 Hz, 1 H), 7.37 (d, J = 8.0 Hz, 1 H), 6.89 (ABq, 4 H), 4.15 (m, 4 H), 3.86 (m, 4 H), 3.71 (m, 4 H), 3.72 (s, 1 H), 3.60 (m, 4 H), 3.38 (s, 6 H).

13C NMR (125 MHz, CDCl3): δ = 159.34, 159.31, 133.26, 133.1, 132.3, 131.0, 130.70, 130.5, 126.6, 114.94, 114.85, 114.73, 114.69, 107.2, 95.9, 95.0, 91.1, 86.8, 85.2, 84.7, 71.9 (2 C), 70.7 (2 C), 69.6 (2 C), 67.5 (2 C), 59.0 (2 C).

MS (EI, 70 eV): m/z (%) = 664 ([M+], 75), 561 (3), 538 (9), 514 (6), 254 (10), 155 (20), 142 (70), 127 (50), 103 (10), 59 (100).

HRMS (EI, 70 eV): m/z [M+] calcd for C34H33IO6: 664.1322; found: 664.1332.

UV/VIS (MeCN): λmax (log ε) = 257 (4.63), 344 (4.77), 354 (sh, 4.75), 362 nm (sh, 4.74).


#

2-Ethynyl-3-iodo-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (20e) from 19e

Compound 19e (1.64 g, 2.00 mmol) in THF (75 mL) was subjected to 1 M TBAF in THF (2.20 mL, 2.20 mmol) at r.t. The solution, which turned yellow immediately, was stirred for 30 min (TLC monitoring), then diluted with CH2Cl2 (200 mL), washed with H2O (3 × 100 mL), and dried (MgSO4). After removal of the volatiles under reduced pressure, column chromatography (silica gel, EtOAc) afforded 20e; yield: 1.29 g (97%).


#

1,4,7,10,13,16-Hexakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-ynyl}tribenzo[a,e,i]cyclododeca-5,11,17-triyne (2d)

To CuCl (99 mg, 1.00 mmol) in aq NH3 (60 mL) was added dropwise 20d (568 mg, 1.00 mmol) in EtOH (60 mL). After stirring for 1 h at r.t., the resulting yellowish orange precipitate was collected by filtration, washed with H2O, and dried under high vacuum overnight. The cuprate was dissolved in pyridine (75 mL) and the solution heated to reflux over a period of 6 h. After cooling to r.t., the volatiles were removed under reduced pressure, and the resulting dark brown residue was subjected to column chromatography (silica gel, Et2O/THF 2:1) to supply 2d as a yellow oil; yield: 104 mg (24%).

IR (film): 2971, 2917, 2868, 2223, 1467, 1375, 1348, 1287, 1247, 1104, 1032, 946, 840, 767, 734, 688, 633 cm–1.

1H NMR (300 MHz, CDCl3): δ = 7.27 (s, 6 H, CH), 4.45 (s, 12 H), 3.74 (AA′m, 12 H), 3.65 (BB′m, 12 H), 3.61 (AA′m, 12 H), 3.55 (BB′m, 12 H), 3.49 (q, J = 7.0 Hz, 12 H), 1.18 (t, J = 7.0 Hz, 18 H).

13C NMR (100 MHz, CDCl3): δ = 132.5, 128.9, 125.6, 95.8, 91.8, 84.1, 70.5, 70.2, 69.6, 69.1, 66.5, 59.1, 15.0.

MS (FAB, 70 eV): m/z (%) = 1321.6 ([MH+]).

UV/VIS (MeCN): λmax (log ε) = 200 (4.55), 232 (sh, 4.41), 247 (4.60), 273 (4.70), 297 (4.68), 311 (4.64), 319 (4.59), 334 (4.81), 400 nm (2.96).


#

1,4,7,10,13,16-Hexakis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)tribenzo[a,e,i]cyclododeca-5,11,17-triyne (2e)

The recipe for the preparation of 2d from 20d was followed, except the solvent for 20e (664 mg, 1.00 mmol) was EtOH/DMSO (1:2, 60 mL). Column chromatography (silica gel, EtOAc/acetone 4:1) sequestered 2e as yellow crystals; yield: 122 mg (23%); mp 118–119 °C (EtOAc­/hexane).

IR (KBr): 3069, 3042, 2923, 2876, 2823, 2198, 1604, 1567, 1511, 1462, 1417, 1356, 1288, 1250, 1199, 1169, 1139, 1127, 1109, 1059, 1028, 923, 830, 764, 627, 608, 535 cm–1.

1H NMR (500 MHz, CDCl3): δ = 7.39 (s, 6 H), 7.16 (d, J = 8.8 Hz, 12 H), 6.60 (d, J = 8.8 Hz, 12 H), 4.08 (AA′m, 12 H), 3.84 (BB′m, 12 H), 3.72 (AA′m, 12 H), 3.58 (BB′m, 12 H), 3.40 (s, 18 H).

13C NMR (125 MHz, CDCl3): δ = 158.6, 133.5, 131.8, 128.6, 126.1, 115.3, 113.9, 96.5, 96.5, 86.9, 71.9, 70.8, 69.7, 67.4, 59.1.

MS (FAB, 70 eV): m/z (%) = 1609.6 ([MH+]).

HRMS (FAB): m/z [M+] calcd for C102H96O18: 1608.6597; found: 1608.6542.

UV/VIS (MeCN): λmax (log ε) = 235 (sh, 4.51), 256 (4.80), 303 (sh, 4.75), 350 (5.20), 378 (sh, 4.99), 439 nm (3.69).

Fluorescence (MeCN, λexc = 350 nm): λem = 499 nm.


#

High Yield Preparation of 12d,e and 14e from 7d,e

(Trimethylsilyl)acetylene (1.14 mL, 786 mg, 8 mmol) or (triisopropylsilyl)acetylene (1.80 mL, 1.46 g, 8 mmol) in a Fisher–Porter bottle was injected in one portion into a mixture of the respective alkynylated 2,3-dibromobenzenes 7d,e (2 mmol), Cl2Pd(PPh3)2 (70 mg, 0.10 mmol), and CuI (19 mg, 0.10 mmol) in Et3N (100 mL) at r.t. The vessel was sealed and the mixture stirred at 100 °C for 6 h. During this time the solution rapidly turned bright yellow, then yellow brown, and finally dark brown with the formation of a precipitate. After cooling to r.t., an additional portion of the silylalkyne (4 mmol) was added, the mixture stirred again at 100 °C for 6 h, allowed to cool to r.t., and filtered. The solvent was evaporated and the resulting residue purified by column chromatography (silica gel, Et2O) to present, respectively, 12d as a yellow oil; yield: 1.00 g (82%); 12e as a yellow oil; yield: 1.10 g (78%); and 14e as yellow crystals; yield: 1.00 g (57%).


#

1,4-Bis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}-2,3-diethynylbenzene (21d)

To 12d (1.22 g, 2.00 mmol) in MeOH (100 mL) was added sat. aq K2CO3­ (1 mL, 8 mmol) at r.t. The resulting cloudy solution was stirred until clear (30 min), diluted with CH2Cl2 (200 mL), washed with H2O (3 × 100 mL), dried (MgSO4), and the volatiles were removed under reduced pressure. Column chromatography (silica gel, Et2O) resulted in 21d as a heat- and light-sensitive, light yellow oil, stored at 0 °C; yield: 910 mg (98%).

IR (film): 3280, 3236, 2974, 2868, 2227, 2105, 1573, 1485, 1461, 1394, 1376, 1349, 1282, 1246, 1101, 1033, 946, 839, 642 cm–1.

1H NMR (300 MHz, CDCl3): δ = 7.34 (s, 2 H), 4.47 (s, 4 H), 3.81 (AA′m, 4 H), 3.70 (BB′′m, 4 H), 3.65 (AA′m, 4 H), 3.61 (s, 2 H), 3.58 (BB′m, 4 H), 3.51 (q, J = 7.0 Hz, 4 H), 1.19 (t, J = 7.0 Hz, 6 H).

13C NMR (100 MHz, CDCl3): δ = 131.3, 127.6, 125.8, 91.3, 85.9, 83.9, 79.8, 70.5, 70.2, 69.6, 68.9, 66.4, 58.8, 15.0.

MS (FAB, 70 eV): m/z (%) = 467 ([MH+]).

UV/VIS (MeCN): λmax (log ε) = 247 (sh, 4.53), 253 (4.61), 257 (4.64), 277 (4.30), 283 (4.34), 294 nm (4.50).


#

2,3-Diethynyl-1,4-bis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}ethynyl)benzene (21e)

From 12e: Compound 12e (1.41 g, 2.00 mmol) was subjected to the reaction conditions used for the synthesis of 21d from 12d. Column chromatography (silica gel, EtOAc) gave 21e as heat- and light-sensitive, light brown needles; yield: 1.04 g (92%); mp >50 °C dec (EtOH).

From 14e: Compound 14e (1.75 g, 2.00 mmol) in THF (75 mL) was exposed to 1 M TBAF in THF (2.2 mL, 2.2 mmol) at r.t. The solution turned yellow immediately and was stirred for 30 min. It was then diluted with CH2Cl2 (200 mL), washed with H2O (3 × 100 mL), dried (MgSO4), and the volatiles removed under reduced pressure. Work up of the residue as described above supplied 21e; yield: 1.11 g (99%).

IR (KBr): 3261, 3073, 2927, 2882, 2829, 2208, 2109, 1602, 1512, 1467, 1450, 1356, 1290, 1252, 1203, 1174, 1163, 1138, 1110, 1057, 982, 949, 939, 923, 845, 828, 809, 769, 714, 664, 615, 533 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.48 (d, J = 8.8 Hz, 4 H), 7.44 (s, 2 H), 6.90 (d, J = 8.8 Hz, 4 H), 4.16 (AA′m, 4 H), 3.87 (BB′m, 4 H), 3.72 (AA′m, 4 H), 3.64 (s, 2 H), 3.58 (BB′m, 4 H), 3.39 (s, 6 H).

13C NMR (100 MHz, CDCl3): δ = 159.3, 133.3, 131.1, 127.4, 126.4, 115.0, 114.7, 95.7, 86.5, 85.4, 80.5, 71.9, 70.8, 69.6, 67.5, 59.0.

MS (FAB, 70 eV): m/z (%) = 562 ([M+]).

UV/VIS (MeCN): λmax (log ε) = 255 (4.52), 266 (sh, 4.46), 346 (4.67), 362 nm (sh, 4.62).


#

1,4,9,12-Tetrakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}dibenzo[a,g]cyclododeca-5,7,13,15-tetrayne (4a) and 1,4,9,12,17,20-Hexakis{3-[2-(2-ethoxyethoxy)ethoxy]prop-1-yn-1-yl}tribenzo[a,g,m]cyclooctadeca-5,7,13,15,21,23-hexayne (22d)

Through a solution of 21d (933 mg, 2.00 mmol) and CuCl (238 mg, 2.40 mmol) in chlorobenzene (125 mL) was passed a continuous stream of dry O2 for 15 min to ensure saturation. TMEDA (10 mL) was then added dropwise under vigorous stirring at r.t. The mixture immediately turned yellow, then green, and finally cloudy dark green with the formation of a precipitate upon completion of the addition. After stirring for an additional 1 h under O2, the reaction was quenched with 1 M aq HCl (100 mL), CH2Cl2 (100 mL) added, the mixture shaken, the organic layer collected, and the aqueous layer further extracted with CH2Cl2 (5 × 100 mL). The combined organic phases were washed with sat. aq NaHCO3 and then H2O. The volatiles were removed under reduced pressure and the resulting solid yellow brown residue was subjected to column chromatography (silica gel, Et2O/THF 5:1), leading to a first fraction containing air-sensitive 4a forming golden plates; yield: 360 mg (39%); mp 104–105 °C dec (CH2Cl2­/hexane).

IR (KBr): 2973, 2911, 2869, 2222, 2121, 1480, 1456, 1443, 1375, 1346, 1289, 1261, 1245, 1118, 1099, 1088, 1029, 951, 852, 835, 664, 626 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.06 (s, 4 H), 4.42 (s, 8 H), 3.73 (AA′m, 8 H), 3.69 (BB′m, 8 H), 3.65 (AA′m, 8 H), 3.60 (BB′m, 8 H), 3.52 (q, J = 7.0 Hz, 8 H), 1.20 (t, J = 7.0 Hz, 12 H).

13C NMR (100 MHz, CDCl3): δ = 133.3, 132.3, 122.8, 91.9, 91.6, 87.3, 83.2, 70.6, 70.3, 69.7, 69.2, 66.5, 58.9, 15.1.

MS (FAB, 70 eV): m/z (%) = 929.5 ([MH+]).

HRMS (FAB, 70 eV): m/z [MH+] calcd for C56H65O12: 929.4476; found: 929.4480.

UV/VIS (MeCN): λmax (log ε) = 212 (4.68), 245 (sh, 4.70), 250 (4.77), 275 (sh, 4.64), 280 (sh, 4.70), 286 (4.81), 295 (sh, 4.63), 302 (sh, 4.51), 317 (4.77), 324 (4.57), 327 (sh, 4.54), 339 (5.06), 420 nm (3.94).

Fluorescence (MeCN, λexc = 340 nm): λem = 501, 539, 548 nm.

On switching the chromatography solvent to Et2O/THF (2:1), a second fraction emerged containing 22d as a yellow oil; yield: 36 mg (4%).

1H NMR (500 MHz, CDCl3): δ = 7.46 (s, 6 H), 4.55 (s, 12 H), 3.85 (AA′m, 12 H), 3.73 (BB′m, 12 H), 3.64 (AA′m, 12 H), 3.58 (BB′m, 12 H), 3.49 (q, J = 7.0 Hz, 12 H), 1.18 (t, J = 7.0 Hz, 18 H).

13C NMR (100 MHz, CDCl3): δ = 132.1, 127.5, 126.6, 92.6, 83.8, 82.0, 80.3, 70.6, 70.4, 69.8, 69.2, 66.6, 59.1, 15.1.


#

1,4,9,12-Tetrakis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}-ethynyl)dibenzo[a,g]cyclododeca-5,7,13,15-tetrayne (4b) and 1,4,9,12,17,20-Hexakis({4-[2-(2-methoxyethoxy)ethoxy]phenyl}-ethynyl)tribenzo[a,g,m]cyclooctadeca-5,7,13,15,21,23-hexayne (22e)

Following the procedure executed for the synthesis of 4a and 22d, oxidative coupling of 21e (1.12 g, 2.00 mmol), followed by column chromatography (silica gel, EtOAc/acetone 4:1), afforded first 4b as air-sensitive yellow crystals; yield: 270 mg (24%); mp 30–40 °C dec (toluene).

IR (KBr): 3070, 3044, 2925, 2876, 2823, 2211, 1604, 1570, 1514, 1474, 1453, 1355, 1285, 1250, 1199, 1167, 1130, 1110, 1059, 923, 827, 649, 605, 535, 487 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.47 (d, J = 8.8 Hz, 8 H), 7.13 (s, 4 H), 6.89 (d, J = 8.8 Hz, 8 H), 4.17 (AA′m, 8 H), 3.88 (BB′m, 8 H), 3.73 (AA′m, 8 H), 3.58 (BB′m, 8 H), 3.39 (s, 12 H).

13C NMR (100 MHz, CDCl3): δ = 159.4, 133.5, 132.9, 132.1, 123.3, 114.73, 114.67, 96.0, 92.1, 87.5, 85.9, 72.0, 70.8, 69.7, 67.5, 59.1.

MS (FAB, 70 eV): m/z (%) = 1120.6 ([M+]).

HRMS (FAB, 70 eV): m/z [M+] calcd for C72H64O12: 1120.4398; found: 1120.4408.

UV/VIS (MeCN): λmax (log ε) = 248 (sh, 4.77), 255 (4.84), 346 (5.05), 367 (5.02), 457 nm (3.94).

Fluorescence (MeCN, λexc = 365 nm): λem = 502, 545, 555 nm.

A second fraction contained waxy, impure 22e, characterized solely by a 1H NMR spectrum; (maximum) yield: 16 mg (1.4%).

1H NMR (300 MHz, CDCl3): δ = 7.53 (s, 6 H), 7.35 (d, J = 8.8 Hz, 12 H), 6.56 (d, J = 8.8 Hz, 12 H), 3.98 (m, 12 H), 3.82 (m, 12 H), 3.72 (m, 12 H), 3.59 (m, 12 H), 3.41 (s, 18 H).


#

Cobalt-Catalyzed Cycloisomerization of 2e to 23

To boiling m-xylene (120 mL) was added 2e (120 mg, 0.075 mmol) and CpCo(CO)2 (33 μL, 45 mg, 0.25 mmol) in m-xylene (30 mL) in one portion. The mixture was maintained at reflux for 25 min, while being irradiated with a 300 W slide projector lamp at 60 V. During this time, the solution turned deep red exhibiting a yellow fluorescence. After removal of the solvent under vacuum, the residue was subjected to column chromatography (silica gel, EtOAc/acetone 3:1) to give 23 as a red solid; yield: 72 mg (60%).

IR (KBr): 2923, 2875, 2824, 2197, 1605, 1511, 1453, 1355, 1287, 1250, 1171, 1128, 1110, 1061, 934, 925, 830, 534 cm–1.

1H NMR (500 MHz, CD2Cl2): δ = 7.36 (s, 2 H), 7.20 (d, J = 8.6 Hz, 4 H), 7.15 (d, J = 8.6 Hz, 4 H), 7.10 (d, J = 7.4 Hz, 2 H), 7.06 (d, J = 8.6 Hz, 4 H), 6.80 (d, J = 8.6 Hz, 4 H), 6.62 (d, J = 7.4 Hz, 2 H), 6.60 (ABq, 8 H), 4.08 (m, 4 H), 4.04 (m, 8 H), 3.80 (m, 12 H), 3.66 (m, 12 H), 3.54 (m, 12 H), 3.36 (s, 12 H), 3.35 (s, 6 H).

13C NMR (125 MHz, CD2Cl2): δ = 159.4, 159.2, 158.8, 151.9, 149.8, 147.1, 134.7, 134.2, 133.9, 132.5, 130.7, 130.6, 129.2, 128.9, 126.6, 125.9, 118.4 (2 C), 116.7, 116.0, 115.7, 114.6, 114.5, 114.4, 97.4, 95.5, 94.9, 94.1, 88.2, 87.4, 72.5 (3 C), 71.24 (2 C), 71.20, 70.20, 70.12, 70.11, 68.10, 68.08, 68.04, 59.3 (3 C).

MS (FAB, 70 eV): m/z (%) = 1609.9 ([MH+]).

HRMS (FAB, 70 eV): m/z [M+] calcd for C102H96O18: 1608.6597; found: 1608.6622.

UV/VIS (MeCN): λmax (log ε) = 261 (5.16), 309 (5.18), 344 (5.32), 422 (4.64), 441 (sh, 4.59), 465 (sh, 4.40), 538 nm (3.78).

Fluorescence (MeCN, λexc = 350 nm): λem = 568 nm.


#

Cobalt-Catalyzed Cycloisomerization of 23 to 24

Angular [3]phenylene derivative 23 (56 mg, 0.035 mmol) and CpCo­(CO)2 (33 μL, 45 mg, 0.25 mmol) in tetraglyme (30 mL) were added in one portion to boiling tetraglyme (120 mL). The mixture was maintained at reflux for 25 min, while being irradiated with a 300 W projector lamp at 60 V. During this time, the solution turned deep red possessing an orange fluorescence. After removal of the solvent under vacuum, the residue was subjected to column chromatography (silica gel, EtOAc/acetone 3:1) to give 24 as a deep red solid; yield: 12 mg (21%).

IR (KBr): 2924, 2855, 2203, 1606, 1511, 1455, 1384, 1355, 1286, 1250, 1199, 1178, 1109, 1063, 927, 825 cm–1.

1H NMR (500 MHz, CD2Cl2): δ = 7.12 (d, J = 8.8 Hz, 4 H), 6.94 (d, J = 8.8 Hz, 4 H), 6.93 (d, J = 8.8 Hz, 4 H), 6.90 (d, J = 7.3 Hz, 2 H), 6.73 (d, J = 8.8 Hz, 4 H), 6.69 (d, J = 8.8 Hz, 4 H), 6.52 (d, J = 8.8 Hz, 4 H), 6.40 (d, J = 7.3 Hz, 2 H), 6.18 (s, 2 H), 4.08 (m, 8 H), 4.00 (m, 4 H), 3.80 (m, 12 H), 3.66 (m, 12 H), 3.54 (m, 12 H), 3.357 (s, 6 H), 3.354 (s, 6 H), 3.349 (s, 6 H).

MS (FAB, 70 eV): m/z (%) = 1609.8 ([MH+]).

HRMS (FAB, 70 eV): m/z [M+] calcd for C102H96O18: 1608.6597; found: 1608.6598.

UV/VIS (MeCN): λmax (A) = 282 (0.44), 296 (sh, 0.40), 347 (0.31), 396 (sh, 0.15), 487 (0.02), 525 (sh, 0.01), 583 nm (0.01).

Fluorescence (MeCN, λexc = 350 nm): λem = 594 nm.


#

3,6,9,16,19,22-Hexaoxatetracosa-11,13-diyne (5a)

Through a solution of 6a (1.72 g, 10 mmol) and CuCl (119 mg, 1.20 mmol) in acetone (75 mL) was passed a continuous stream of dry O2 for 15 min to ensure saturation. TMEDA (1 mL) was then added in one portion under vigorous stirring at r.t. The mixture immediately turned green and then dark green with the formation of a precipitate. After stirring for an additional 4 h under O2, the reaction was quenched with 1 M aq HCl (75 mL), CH2Cl2 (100 mL) added, the mixture shaken, the organic layer collected, and the aqueous layer further extracted with CH2Cl2 (5 × 100 mL). The combined organic phases were washed with sat. aq NaHCO3, then H2O, and finally dried (MgSO4­). The volatiles were removed under reduced pressure, and the resulting solid yellow brown residue was subjected to column chromatography (silica gel, Et2O) to provide 5a as a light-sensitive, light yellow oil; yield: 1.41 g (82%).

IR (film): 2974, 2869, 2253, 2177, 2120, 1486, 1457, 1443, 1376, 1348, 1290, 1246, 1093, 1030, 999, 945, 921, 844 cm–1.

1H NMR (300 MHz, CDCl3): δ = 4.27 (s, 4 H), 3.68 (m, 8 H), 3.65 (AA′m, 4 H), 3.60 (BB′m, 4 H), 3.52 (q, J = 7.0 Hz, 4 H), 1.21 (t, J = 7.0 Hz, 6 H).

13C NMR (100 MHz, C6D6): δ = 76.8, 71.4, 71.2, 71.1, 70.7, 70.1, 67.0, 59.1, 15.8.

MS (FAB, 70 eV): m/z (%) = 343.2 ([MH+]).

HRMS (FAB, 70 eV): m/z [MH+] calcd for C18H31O6: 343.2121; found: 343.2119.


#

1,4-Bis{4-[2-(2-methoxyethoxy)ethoxy]phenyl}buta-1,3-diyne (5b)

In a replication of the manner in which 5a was assembled, 6b (2.20 g, 10 mmol) was subjected to oxidative coupling and purified by column chromatography (silica gel, EtOAc) to create 5b as colorless crystals; yield: 1.98 g (90%); mp 84–85 °C (EtOH).

IR (KBr): 3074, 3045, 2971, 2943, 2913, 2878, 2140, 1639, 1599, 1504, 1466, 1451, 1399, 1380, 1357, 1307, 1285, 1248, 1201, 1171, 1141, 1120, 1079, 1058, 1032, 960, 953, 942, 923, 851, 829, 721, 640, 574, 537, 456 cm–1.

1H NMR (400 MHz, CDCl3): δ = 7.44 (d, J = 6.0 Hz, 4 H), 6.86 (d, J = 6.0 Hz, 4 H), 4.15 (AA′m, 4 H), 3.86 (BB′m, 4 H), 3.71 (AA′m, 4 H), 3.57 (BB′m, 4 H), 3.39 (s, 6 H).

13C NMR (100 MHz, CDCl3): δ = 159.3, 133.9, 114.7, 113.9, 81.1, 72.9, 71.8, 70.6, 69.5, 67.4, 58.9.

MS (FAB, 70 eV): m/z (%) = 438 ([M+]).

UV/VIS (MeCN): λmax (log ε) = 203 (4.74), 242 (sh, 4.28), 260 (sh, 4.41), 268 (4.47), 281 (4.50), 299 (4.56), 319 (4.65), 340 nm (3.54).


#
#

Acknowledgment

U.D. thanks the Alexander von Humboldt Foundation for a Feodor Lynen­ Research Fellowship.

Supporting Information

    Supporting information for this article is available online at https://doi-org.accesdistant.sorbonne-universite.fr/10.1055/s-0039-1690050.
  • Supporting Information


   Permissions and Reprints All articles of this category
Zoom Image
Figure 1 Retrosynthetic disconnection of the circular [6]phenylene frames 1 and 3 to the ethynylated benzocyclynes 2 and 4, respectively
Zoom Image
Scheme 1 Alkynylation of 1,2,3,4-tetrabromobenzene with 6a and 6b, respectively, to assemble 7d,e–9d,e; tetraalkynyl derivative 10d is generated during the alkynylation of 8d with 6a, in addition to 7d and 9d
Zoom Image
Scheme 2 Various monoalkynylations of 7d,e
Zoom Image
Scheme 3 Bromine–iodine exchange of 7d,e to give 17d,e and subsequent (trimethylsilyl)ethynylation to 11d,e and 12d,e
Zoom Image
Scheme 4 Preparation of targets 2d,e through bromine–iodine exchange of 11d,e to give 18d,e, subsequent deprotection, and cyclization
Zoom Image
Scheme 5 Synthesis of benzocyclynes 4a,b and 22d,e starting from dibromides 7d,e
Zoom Image
Scheme 6 Attempted CpCo-catalyzed cycloisomerization of 2e to 1e via 23 and 24