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Synlett 2010(11): 1679-1681  
DOI: 10.1055/s-0029-1219957
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis and Structures of 1,10-Phenanthroline-Based Extended Triptycene Derivatives

Yi Jianga,b, Chuan-Feng Chen*a
a Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. of China
Fax: +86(10)62554449; e-Mail: cchen@iccas.ac.cn;
b Graduate School, Chinese Academy of Sciences, Beijing 100049, P. R. of China

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Publication History

Received 7 April 2010
Publication Date:
04 June 2010 (online)

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Abstract

A series of novel 1,10-phenanthroline-based extended triptycene derivatives were conveniently synthesized in good yields, and their structures were determined by ¹H NMR, ¹³C NMR, MALDI-TOF MS spectra, and elemental analysis.

Key words

triptycene - 1,10-phenanthroline - synthesis

Triptycene [¹] and its derivatives are a class of interesting compounds with unique three-dimensional rigid frameworks. They have been found wide potential applications in synthetic molecular machines, [²] materials science, [³] and supramolecular chemistry. [4] Triptycene skeleton could be extended by increasing the size of its arene blades, which provided chances for the synthesis of higher iptycenes. [5] [6] Recently, King [7] reported a triphenylene-based triptycene, which was extended both parallel and perpendicular to its highest symmetry axis to result in large internal molecular free volumes (IMFV). [8] Although the triptycenes with large IMFV might play an important role in their practical applications, relevant examples are still rare.

In recent years, we became interested in developing new supramolecular systems based on the triptycene-derived synthetic receptors. [9] Consequently, some of new triptycene derivatives with specific structures and properties are needed. As a part of our continuing work, we herein report the facile synthesis of a series of extended triptycene derivatives by the condensation of 1,10-phenanthroline-5,6-quinones with 2,3-diaminotriptycene or 2,3,6,7,14,15-hexaaminotriptycene. These extended triptycene derivatives containing phenanthroline moiety [¹0] show large IMFV, and can subsequently find wide potential applications in the development of new supramolecular systems and construction of functional materials.

According to a modified literature procedure, [¹¹] we first prepared the 1,10-phenanthroline-5,6-quinone derivatives 3a-c in good yields by the oxidation of phenanthroline derivatives 6a-c [¹²] (Scheme  [¹] ). Similarly, we also obtained compound 3d in 65% yield by the oxidation of 6d at room temperature. [¹³] It was found that the temperature was important to the oxidation reaction. As a result, it was found that no product could be obtained when the reaction temperature of 6d was above 60 ˚C.

Scheme 1 Synthesis of 1,10-phenanthroline-5,6-quinones 3

Scheme 2 Synthesis of extended triptycene derivatives 2a-d

With the phenanthroline derivatives 3a-d in hand, we then performed the condensation of 3a-d and 2,3-diaminotriptycene 4 [¹4] in refluxed methanol. The reaction took place smoothly to give the extended triptycene derivatives 2a-d in good yields (Scheme  [²] ). [¹5] It was found that compounds 2a-d have good solubility in chloroform and dichloromethane. In the ¹H NMR spectra of 2a-d, one singlet signal for the bridgehead proton and another singlet signal for the aromatic proton Ha were observed. Meanwhile, their ¹³C NMR spectra all showed one signal for the bridgehead carbon and 12 signals for the aromatic carbons. These observations were consistent with their C 2 symmetry. Moreover, the structures of 2a-d were also confirmed by their MALDI-TOF MS spectra and elemental analysis.

When compound 3a or 3b was reacted with 2,3,6,7,14, 15-hexaaminotriptycene 5, [¹4] we obtained yellow solids with low solubilities. MALDI-TOF MS spectra suggested the structures of targeted molecules 1a and 1b, but it was difficult to further confirm them by ¹H NMR and ¹³C NMR spectra because of their poor solubilities. However, when 3c was reacted with 5, we found that the extended triptycene derivative 1c could be synthesized in 28% yield (Scheme  [³] ). [¹6] Similarly, 1d was obtained in 32% yield from the reaction of 3d with 5. Compounds 3c and 3d were all purified by silica gel column chromatography, and confirmed by ¹H NMR, ¹³C NMR, MALDI-TOF MS spectra, and elemental analysis. Moreover, it was found that both of 1c and 1d have good solubilities in common solvents including chloroform, THF, DMF, and dichloromethane.

Scheme 3 Synthesis of extended triptycene derivatives 1c and 1d

Figure 1 Partial ¹H NMR spectra (300Hz, CDCl3) of (1) 1c and (2) 1d; resonance protons are labeled in Scheme 3

The partial ¹H NMR spectra of both 1c and 1d were shown in Figure  [¹] . One singlet (Hd) for the bridgehead proton and three signals (Hb-Hd) for the aromatic protons were found. Moreover, the ¹³C NMR spectra of both 1c and 1d only showed one signal for the bridgehead carbon and nine signals for the aromatic carbons. These results suggested they all have high D 3 v symmetry. Compared with 1c, the signals of protons Hb-Hd of 1d shifted obviously upfield while Ha shifted downfield, which was probably due to the stronger electron-donating ability of tert-butyl of 1d. Moreover, we also calculated the structures of 1c and 1d by AM1 method, and the IMFV of 1c and 1d were found to be about 1150 ų, which is significantly larger than that reported by King. [7]

In summary, we have shown a facile approach to synthesize a series of 1,10-phenanthroline-based extended triptycene derivatives via the condensation of 2,3-diamino-triptycene or 2,3,6,7,14,15-hexaaminotriptycene with 1,10-phenanthroline-5,6-quinone derivatives. The useful 1,10-phenanthroline blocks were induced to triptycene skeleton to form new rigid scaffold geometry and generate large IMFV, which might be found potential applications in molecular assemblies and material chemistry.

Supporting Information for this article is available online at http://www.thieme-connect.com.accesdistant.sorbonne-universite.fr/ejournals/toc/synlett.

Acknowledgment

We thank the National Natural Science Foundation of China (20625206, 20772126), the National Basic Research Program (2009ZX09501-018) and the Chinese Academy of Sciences for financial support.

13

Preparation and Spectroscopic Data of 3d An ice-cold mixture of concentrated H2SO4 (10 mL) and HNO3 (5 mL) was added to 6d (438 mg, 1.5 mmol) and of KBr (1 g, 8.4 mmol). The mixture was reacted at r.t. for 8 h. The yellow solution was poured to over 500 mL of ice, neutralized carefully with NaOH until neutral to slightly acidic pH, and extracted with CHCl3 followed by drying with Na2SO4 and removal of solvent. The crude product was purified by silica gel column chromatography (eluant: PE-CH2Cl2 = 2:3) to afford 3d in 65% yield as white solid; mp 144-146 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 8.37 (d, J = 8.3 Hz, 2 H), 7.58 (d, J = 8.3 Hz, 2 H), 1.52 (s, 18 H). ¹³C NMR (75 MHz, CDCl3): δ = 179.3, 177.1, 152.3, 137.1, 125.8, 121.0, 39.1, 29.8. MS (EI): m/z = 322 [M+]. Anal. Calcd for C20H22N2O2: C, 74.51; H, 6.88; N, 8.69. Found: C, 74.34; H, 6.69; N, 8.57.

15

Experimental Procedure and Characterizations for Representative Compound 2a
To a solution of compound 4 (284 mg, 1 mmol) in MeOH (50 mL) was added 3a (273 mg, 1.3 mmol). The solution was stirred under N2 overnight to give a yellow solution. The solvent was removed by rotary evaporation, and the red-orange residue was purified by silica gel column chromatog-raphy (eluant: MeOH-CH2Cl2 = 1:100) to give the product 2a in 67% yield as yellow solid; mp >300 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 9.45 (dd, J = 1.8, 6.3 Hz, 2 H), 9.17 (dd, J = 1.8, 2.7 Hz, 2 H), 8.19 (s, 2 H), 7.63-7.59 (m, 2 H), 7.55-7.51 (m, 4 H), 7.15-7.11 (m, 4 H), 5.74 (s, 2 H). ¹³C NMR (75 MHz, CDCl3): δ = 152.0, 147.7, 147.0, 143.6, 141.6, 140.0, 133.2, 127.3, 126.2, 124.2, 123.8, 122.8, 53.8. MS (MALDI-TOF): m/z = 459.2 [M + H]+, 481.1 [M + Na]+, 497.1 [M + K]+. Anal. Calcd for C32H18N4: C, 83.82; H, 3.96; N, 12.22. Found: C, 83.71; H, 4.13; N, 12.14.

16

Experimental Procedure and Characterizations for Representative Compound 1c To a solution of compound 5 (344 mg, 1 mmol) in MeOH (50 mL) was added 3c (1.38 g, 4.3 mmol). The solution was stirred under N2 overnight to give a yellow solution. The solvent was removed by rotary evaporation, and the red-orange residue was purified by silica gel column chromatog-raphy (eluant: MeOH-CH2Cl2 = 1:50) to give the product 1c in 28% yield as yellow solid; mp >300 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 9.55 (d, J = 8.3 Hz, 6 H), 8.54 (s, 6 H), 7.69 (d, J = 8.3 Hz, 6 H), 6.36 (s, 2 H), 3.35-3.29 (m, 12 H), 1.90-1.89 (m, 12 H), 1.57-1.50 (m, 12 H), 1.02 (t, J = 7.3 Hz, 18 H). ¹³C NMR (75 MHz, CDCl3): δ = 165.9, 147.5, 143.5, 141.4, 140.8, 133.4, 124.9, 124.2, 123.0, 53.3, 39.0, 31.8, 22.9 14.1. MS (MALDI-TOF): m/z = 1203.6 [M + H]+. Anal. Calcd for C78H74N12 ˙H2O: C, 78.23; H, 6.40; N, 14.04. Found: C, 78.34; H, 6.23; N, 13.91.

13

Preparation and Spectroscopic Data of 3d An ice-cold mixture of concentrated H2SO4 (10 mL) and HNO3 (5 mL) was added to 6d (438 mg, 1.5 mmol) and of KBr (1 g, 8.4 mmol). The mixture was reacted at r.t. for 8 h. The yellow solution was poured to over 500 mL of ice, neutralized carefully with NaOH until neutral to slightly acidic pH, and extracted with CHCl3 followed by drying with Na2SO4 and removal of solvent. The crude product was purified by silica gel column chromatography (eluant: PE-CH2Cl2 = 2:3) to afford 3d in 65% yield as white solid; mp 144-146 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 8.37 (d, J = 8.3 Hz, 2 H), 7.58 (d, J = 8.3 Hz, 2 H), 1.52 (s, 18 H). ¹³C NMR (75 MHz, CDCl3): δ = 179.3, 177.1, 152.3, 137.1, 125.8, 121.0, 39.1, 29.8. MS (EI): m/z = 322 [M+]. Anal. Calcd for C20H22N2O2: C, 74.51; H, 6.88; N, 8.69. Found: C, 74.34; H, 6.69; N, 8.57.

15

Experimental Procedure and Characterizations for Representative Compound 2a
To a solution of compound 4 (284 mg, 1 mmol) in MeOH (50 mL) was added 3a (273 mg, 1.3 mmol). The solution was stirred under N2 overnight to give a yellow solution. The solvent was removed by rotary evaporation, and the red-orange residue was purified by silica gel column chromatog-raphy (eluant: MeOH-CH2Cl2 = 1:100) to give the product 2a in 67% yield as yellow solid; mp >300 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 9.45 (dd, J = 1.8, 6.3 Hz, 2 H), 9.17 (dd, J = 1.8, 2.7 Hz, 2 H), 8.19 (s, 2 H), 7.63-7.59 (m, 2 H), 7.55-7.51 (m, 4 H), 7.15-7.11 (m, 4 H), 5.74 (s, 2 H). ¹³C NMR (75 MHz, CDCl3): δ = 152.0, 147.7, 147.0, 143.6, 141.6, 140.0, 133.2, 127.3, 126.2, 124.2, 123.8, 122.8, 53.8. MS (MALDI-TOF): m/z = 459.2 [M + H]+, 481.1 [M + Na]+, 497.1 [M + K]+. Anal. Calcd for C32H18N4: C, 83.82; H, 3.96; N, 12.22. Found: C, 83.71; H, 4.13; N, 12.14.

16

Experimental Procedure and Characterizations for Representative Compound 1c To a solution of compound 5 (344 mg, 1 mmol) in MeOH (50 mL) was added 3c (1.38 g, 4.3 mmol). The solution was stirred under N2 overnight to give a yellow solution. The solvent was removed by rotary evaporation, and the red-orange residue was purified by silica gel column chromatog-raphy (eluant: MeOH-CH2Cl2 = 1:50) to give the product 1c in 28% yield as yellow solid; mp >300 ˚C. ¹H NMR (300 MHz, CDCl3): δ = 9.55 (d, J = 8.3 Hz, 6 H), 8.54 (s, 6 H), 7.69 (d, J = 8.3 Hz, 6 H), 6.36 (s, 2 H), 3.35-3.29 (m, 12 H), 1.90-1.89 (m, 12 H), 1.57-1.50 (m, 12 H), 1.02 (t, J = 7.3 Hz, 18 H). ¹³C NMR (75 MHz, CDCl3): δ = 165.9, 147.5, 143.5, 141.4, 140.8, 133.4, 124.9, 124.2, 123.0, 53.3, 39.0, 31.8, 22.9 14.1. MS (MALDI-TOF): m/z = 1203.6 [M + H]+. Anal. Calcd for C78H74N12 ˙H2O: C, 78.23; H, 6.40; N, 14.04. Found: C, 78.34; H, 6.23; N, 13.91.

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Scheme 1 Synthesis of 1,10-phenanthroline-5,6-quinones 3

Scheme 2 Synthesis of extended triptycene derivatives 2a-d

Scheme 3 Synthesis of extended triptycene derivatives 1c and 1d

Figure 1 Partial ¹H NMR spectra (300Hz, CDCl3) of (1) 1c and (2) 1d; resonance protons are labeled in Scheme 3