Modular Approach to the Synthesis of Polydentate NHC-Ligand Precursors (Benzimidazolium Salts) Containing Axial Chiral 1,1′-Binaphthyl via Pd-Catalyzed N-Arylation of 1,2-Diaminobenzene

Abstract

A convenient and efficient modular approach to the synthesis of polydentate NHC ligand precursors (benzimidazolium salts) containing axial chiral 1,1′-binaphthyl from 1,2-diaminobenzene and BINOL has been developed. The benzimidazolium salts could be regarded as the potential bidentate, tridentate, and tetradentate NHC ligand precursors.

In the past two decades, N-heterocyclic carbene (NHC) has emerged as an important class of ligand with various applications in organometallic chemistry due to its strong σ-donating capability and low level of π-acidity.[1] [2] Among all the properties of NHC ligand, one of the most attractive features probably is the variability of the substituents on the nitrogen atoms, which allows for a wide range of steric, electronic, and asymmetric tuning. Additionally, it is also possible to change these nitrogen substituents to make the NHC ligands capable of chelation. Such variability has led to the synthesis of NHC analogues of many traditional ligands.[3] Salicylaldimines is one type of the most successful polydentate chelating ligands in organometallic chemistry.[4] The salicylaldimines could be bidentate, tridentate, or tetradentate, which could meet the demands of metals with different coordinating geometry. The salicylaldimine metal complexes have been found applications in a variety of organic transformations.[1] [2] Inspired by the unique salicylaldimines (sal) framework, and also as one of our ongoing goals to design and synthesize new chiral polydentate ligands, herein we would like to report a modular approach to polydentate NHC ligand precursors (benzimidazolium salts). These potential NHC ligands are analogues to those polydentate sal or salen ligands in terms of both the structures and chelating modes (Figure [1]).

Previously, we reported a modular approach to the vicinal diamines containing axial chiral 1,1′-binaphthyl from 1,2-diaminoethane by Pd-catalyzed N-arylation reactions.[5] The resulting diamines were then converted into the corresponding chiral imidazolinium salts, which could be used as the NHC ligand precursors. As mentioned above, we are very much interested in the C ₂-symmetric imidazolinium salt A, which is a potential precursor of the tridentate NHC ligand. However, the efforts to produce the corresponding free NHC or synthesize M-NHC complex eventually proved unsuccessful (Scheme [1]). For example, transmetalation from Ag-NHC complex to other metal complexes has been employed in many catalytic systems. The formation of Ag-NHC from imidazolinium salt and Ag₂O is one of the most reliable and convenient procedures in literature.[6] However, when the imidazolinium salt A (R = H) was subjected to Ag₂O, an interesting ring-opening spirocyclic product B, which was confirmed by X-ray diffraction analysis, rather than the Ag-NHC complex, was formed. A variety of different methods and metals (Cu, Ag, Au, Pd) were also tried in order to synthesize the M-NHC complex. Unfortunately, only the ring-opening products C or D were obtained. Further investigation showed that the imidazolinium A is unstable in both acidic and basic conditions. Even in the solid state, A (R = Me) could slowly decompose into C as well.

The instability of imidazolinium A (1st generation) could be presumably attributed to the single bond (Scheme [2], marked by arrow a in molecule A) in the imidazolinium ring and the electron-rich carbon center on the axial head (Scheme [2], marked by arrow b in molecule A). We envisioned that this problem could be solved by simply moving one carbon away from the chiral axial and changing the C–C bond to C=C bond (Scheme [2]). We believed the imidazolium salt would become more stable by such modification. Furthermore, the 2nd generation imidazolium salts would serve as the precursors of polydentate (bidentate, tridentate, and tetradentate) NHC ligands as well.

With this in mind, the retrosynthetic analysis was then made (Scheme [3]). According to the retrosynthetic analysis, the benzimidazolium salt was chosen to replace the original dihydroimidazolium salt in order to introduce the C=C bond. The benzimidazolium salt IM could be synthesized easily from 1,2-diaminobenezene and halide F through a Pd-catalyzed N-arylation process. And the halide F could be synthesized readily from simple BINOL.

Synthesis of Bidentate Imidazolium Salts

In order to synthesize the target benzimidazolium salt IM, the corresponding halides 3 have to be prepared. Starting from the triflate 1, the halides 3 could be easily prepared in two steps in good yields (Scheme [4]). Initially, MOMO-protected binaphthyl 2 was obtained from the reaction of triflate 1 and the corresponding Grignard reagents in excellent yields, which is a Ni-catalyzed cross-coupling process. Treatment of 2 with BuLi, followed by addition of I₂ gave the desired products 3 in almost quantitative yields.

With the iodides 3 in hand, we then set out to synthesize the corresponding polydentate benzimidazolium salts. Initial efforts were made to investigate various catalytic conditions for N-arylation reactions of iodides 3 with 1,2-diaminobenzene. When excess 1,2-diaminobenzene (1.5 equiv) was employed for the N-arylation reaction with Pd(OAc)₂ as catalyst and BINAP as ligand, 4a and 4b could be prepared in 91% and 94% yield, respectively. Under the similar reaction conditions (DPE-phos as ligand, and toluene as solvent), the mono-substituted diaminobenzene derivatives 4 could be smoothly cross-coupled with a second molecule of ArBr or ArOTf. It gave the desired disubstituted diaminobenzenes 5 in 59–89% yields (Scheme [5]).

With these versatile vicinal diamines 5 containing axial chiral 1,1′-binaphthyl in hand, we then worked on their potential applications for the synthesis of benzimidazolium salts. By simply following the literature procedure[5] with small modification, eight different benzimidazolium salts 6a–h were synthesized in good yields (61–79%) (Scheme [6]).

In the presence of a catalytic amount of TsOH, the reaction of mono-substituted diaminobenzenes 4 and HC(OEt)₃ gave the ring-closure product benzimidazoles 7a and 7b in 91% and 97% yield, respectively. The benzimidazoles 7 then nucleophilically attacked the alkyl halide affording another type of bidentate imidazolium salts 6i–l (Scheme [7]).

Synthesis of Tridentate and Tetradentate Imidazolium Salts

Polydentate ligands with transition-metal complexes are frequently encountered in catalytic process. Most such complexes are typically bench-stable due to the chelating effects. Bidentate NHC ligands have been already successfully applied in a variety of transformation. However, the synthesis and application of tridentate or tetradentate NHC-metal complexes are rarely seen in the literature. We are particularly interested in the synthesis and application of the chiral polydentate NHC-metal complexes. After successfully preparing the bidentate benzimidazolium 6a–l, the synthesis of different tridentate and tetradentate NHC precursors was carried out. As shown in Scheme [8], we initially tried to selectively prepare C₂-symmetric disubstituted amine 8 by controlling the ratios of the starting materials. C₂-Symmetric disubstituted amine 8 could be selectively formed in good yields when simply changing the ratio of halide 3 to 1,2-diaminobenzene from 1.0:1.5 to 3.0:1.0. Following similar procedure, three different C₂-symmetric imidazole salts 9a–c could be synthesized in good yields (59–72%) (Scheme [8]). Among them, imidazolium salts 9a and 9b have two hydroxyl groups and one potential carbene carbon.

Tetradentate Imidazolium Salts

In the past decades, tetradentate salen ligand derived from salicylaldehyde was one of the most successful ligands in organic synthesis. However, the salen complexes are normally applied in basic reaction conditions, as the imine C=N bond are sensitive to the acidic conditions, which severely limited their applications and scope. The NHC ligand, with its strong electron-donating properties, can form M-NHC tightly. Most M-NHC complexes have good stabilities to water, oxidizing reagents, and acid, which enable NHC being a more useful ligand in harsh reaction conditions, such as strong acidic[7] or oxidizing conditions.[8] For these reasons, the tetradentate M-NHC complexes would hold special attraction to organic chemists. As the benzimidazoles 7 were successfully synthesized as shown in Scheme [7], their further transformations with dihalides were then investigated. The resulting imidazoliums possess two potential carbene carbons and two hydroxyl groups, which could be regarded as tetradentate NHC ligand precursors. In this transformation, 1,4-dioxane was chosen as the solvent and different alkyl dihalides were tested (Scheme [9]). The results showed that the reactions were highly sensitive to the steric hindrance of the substrates 7 and dihalides. For example, only trace product could be detected when phenyl-substituted benzimidazole 7a was used as the substrate (10a, 10c, 10e, 10g), while benzimidazole 7b with a smaller substituent (methyl group) could furnish the desired products. However, this reaction also has high restrictions on the structure of the dihalide (X–A–X). CH₂X₂ (X = Br or I) and BrCH₂CH₂CH₂Br, which were used most commonly for the preparation of diimidazolium salts, could not react with 7 affording the desired benzimidazolium salts. However, the m- and p-xylylene dibromide could react with methyl-substituted imidazole 7b leading to the corresponding imidazolium salts 10b and 10d in satisfactory yields.

As pointed out above, imidazoliniums A are bench-unstable (Scheme [1]). After obtaining the imidazoliums 6, 9, and 10, their stability was investigated. Six benzimidazolium salts 6a, 6b, 6k, 9a, 10b, and 10d were representatively selected to study their stability under high temperature (110 °C) for 24 hours. As expected, all the benzimidazolium salts were recovered almost in quantitative yields (Scheme [10]).

In conclusion, we have developed a convenient and efficient modular approach to the synthesis of polydentate NHC ligand precursors (benzimidazolium salts) containing axial chiral 1,1′-binaphthyl from 1,2-diaminobenzene by Pd-catalyzed N-arylation reactions. These benzimidazolium salts could be bidentate, tridentate, and tetradentate. We believe these structure-interesting benzimidazolium salts, particularly the C ₂-symmetric one, will find broad applications in the asymmetric catalytic processes. Further applications of these benzimidazolium salts in catalytic process are undertaken in our laboratory.

¹H and ¹³C NMR spectra were recorded on Bruker DRX-400 spectrometer using CDCl₃ or DMSO-d ₆ as solvent and TMS as an internal standard. Data are reported as follows: chemical shift, integration, multiplicity (standard abbreviations), coupling constants (Hz). ¹³C NMR spectra are recorded on a Bruker DRX-400 (100 MHz) with complete proton decoupling. IR spectra are recorded on a Nicolet 210 spectrophotometer.

Unless otherwise noted, the following materials were purified by distillation over Na under positive pressure of dry N₂: 1,4-dioxane, toluene, HC(OEt)₃, THF, and Et₂O. The following materials were purchased from commercial sources and used as received: (R)-(+)-BINOL, bromobenzene, 2-bromo-1,3,5-trimethylbenzene, 1-bromo-3,5-di-tert-butylbenzene, 2-bromo-1,3-diisopropylbenzene, 1-bromonaphthalene, TsOH, I₂, PhMgBr, MeMgBr, benzene-1,2-diamine, MeI, PhCH₂Br, 1,3-bis(bromomethyl)benzene, 1,2-bis(bromomethyl)benzene, and 1,4-bis(bromomethyl)benzene.

2-Methoxymethoxy-2′-trifluoromethanesulfoxy-1,1′-binaphthyl (1)[9]

To a solution of (R)-(+)-BINOL (5.73 g, 20 mmol) and i-Pr₂NEt (3.48 mL, 20 mmol) in CH₂Cl₂ (100 mL) was added Tf₂O (3.36 mL, 20 mmol) at 0 °C under N₂. The reaction mixture was stirred for 30 min and quenched with sat. aq NaHCO₃ (50 mL). Extractive workup was performed with CH₂Cl₂ (3 × 50 mL) and the combined extracts were washed with brine (100 mL) and dried (Na₂SO₄). After evaporation of solvents and drying under vacuum, the crude product was dissolved in THF (80 mL) under N₂. To this solution was added NaH (0.96 g, 60% dispersion in mineral oil, 24 mmol) at 0 °C by portions, and the reaction mixture was maintained at the same temperature for 15 min with stirring. Chloromethyl methyl ether (1.82 mL, 24 mmol) was added dropwise to the solution at 0 °C, and stirring was continued for 3 h at r.t. The reaction was quenched with H₂O (30 mL) and extractive workup was conducted with EtOAc (3 × 50 mL). The combined organic extracts were washed with brine (80 mL) and dried (Na₂SO₄). Removal of solvents and purification of the residual oil by column chromatography on silica gel (EtOAc–hexanes, 1:10) afforded 1 as a white powder; yield: 8.9 g (19.4 mmol, 97%); mp 73–74 °C.

¹H NMR (400 MHz, CDCl₃): δ = 3.22 (3 H, s), 5.03 (1 H, d, J = 7.2 Hz), 5.19 (1 H, d, J = 7.2 Hz), 7.04 (1 H, d, J = 9.6 Hz), 7.39 (3 H, m), 7.55–7.57 (2 H, m), 7.62–7.64 (1 H, m), 7.87–7.89 (1 H, m), 7.96–8.05 (3 H, m).

¹³C NMR (100 MHz, CDCl₃): δ = 55.9, 94.9, 115.9, 116.4, 119.6, 124.2, 125.1, 126.8, 126.9, 126.9, 127.3, 127.4, 128.1, 128.2, 129.5, 130.3, 131.1, 132.6, 133.5, 133.7, 145.5, 153.2.

(R)-3-Iodo-2-(methoxymethoxy)-1-(2-phenylnaphthalen-1-yl)naphthalene (3a)

(R)-2-(Methoxymethoxy)-1-(2-phenylnaphthalen-1-yl)naphthalene (2a):[5] To a solution of 1 (16.0 g, 35.0 mmol) and NiCl₂(dppe) (1.3 g, 2.5 mmol) in Et₂O (300 mL) was added PhMgBr (70 mL, 70 mmol) at 0 °C under N₂. The reaction mixture was stirred for 24 h and the quenched with sat. aq NaHCO₃ (100 mL). The organic layer was washed with brine (80 mL) and dried (Na₂SO₄). After removal of solvents and purification of the residual oil by column chromatography on silica gel (EtOAc–hexanes, 1:30), 2a (11.1 g) was obtained as a white powder: yield: 11.1 g (81%); mp 114–115 °C.

¹H NMR (400 MHz, CDCl₃): δ = 3.09 (3 H, s), 4.76 (1 H, d, J = 8 Hz), 4.89 (1 H, d, J = 8 Hz), 7.01–7.02 (3 H, m), 7.11–7.14 (3 H, m), 7.19–7.29 (5 H, m), 7.41–7.44 (2 H, m), 7.66 (1 H, d, J = 8 Hz), 7.77–7.82 (2 H, m), 7.93 (1 H, d, J = 8 Hz), 8.00 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 55.7, 95.0, 116.3, 125.8, 126.41, 126.44, 126.8, 127.3, 127.94, 127.99, 128.8, 129.5, 152.8.

Iodination of 2a to 3a : To a solution of 2a (2.0 g, 5.0 mmol) in Et₂O (100 mL) was added BuLi (4.2 mL, 10.0 mmol, N = 2.4 M) at 0 °C under N₂. The reaction mixture was stirred for 4 h, and then treated with a solution of I₂ (2.5 g, 10.0 mmol) in THF (20 mL) at 0 °C under N₂. The mixture was stirred for 4 h and then quenched with sat. aq Na₂SO₃ (50 mL). Extractive workup was performed with EtOAc (3 × 50 mL), and the combined extracts were washed with brine (50 mL) and dried (Na₂SO₄). Removal of solvents and purification of the residual oil by column chromatography on silica gel (EtOAc–hexanes, 1:30) furnished 3a as a white powder; yield: 2.5 g (95%); mp 90–91 °C; [α]_D ²⁰ +41.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3473.3, 2955.7, 2923.7, 2852.7, 1623.3, 1495.4, 1462.8, 1261.8, 1154.3, 982.9, 952.5, 750.1, 700.9 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.65 (3 H, s), 4.44 (1 H, d, J = 4 Hz), 4.75 (1 H, d, J = 4 Hz), 7.03–7.09 (5 H, m), 7.19–7.36 (5 H, m), 7.46–7.50 (1 H, m), 7.65 (1 H, d, J = 8 Hz), 7.69 (1 H, d, J = 8 Hz), 7.93 (1 H, d, J = 8 Hz), 8.01 (1 H, d, J = 8 Hz), 8.36 (1 H, s).

¹³CNMR (100 MHz, CDCl₃): δ = 56.6, 92.6, 98.7, 125.5, 125.8, 126.6, 126.64, 126.9, 126.91, 127.0, 127.5, 127.9, 128.4, 128.5, 128.6, 128.9, 131.0, 131.9, 132.6, 133.3, 134.4, 139.9, 140.8, 141.5, 151.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₂₈H₂₁IO₂ + H: 517.0659; found: 517.0661.

(S)-1-[2-(Methoxymethoxy)naphthalen-1-yl]-2-methylnaphthalene (2b)

This compound was prepared from 1 and MeMgBr by the same procedure as described for the synthesis of 2a. After purification on silica gel (EtOAc–hexanes, 1:30), 2b was obtained as a white powder; yield: 10.9 g (95%); mp 107–108 °C.

¹H NMR (400 MHz, CDCl₃): δ = 2.10 (3 H, s), 3.06 (3 H, s), 4.96 (2 H, s), 7.02 (1 H, d, J = 8 Hz), 7.12–7.16 (3 H, m), 7.29–7.33 (2 H, m), 7.46 (1 H, d, J = 8 Hz), 7.53 (1 H, d, J = 8 Hz), 7.82 (3 H, d, J = 8 Hz), 7.89 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.5, 55.92, 95.0, 117.1, 124.3, 125.4, 126.0, 126.1, 126.7, 128.0, 128.1, 128.8, 129.5, 152.3.

(S)-1-[3-Iodo-2-(methoxymethoxy)naphthalen-1-yl]-2-methylnaphthalene (3b)

This compound was prepared from 2b (5.0 mmol) by the same procedure as described for the synthesis of 3a from 2a. After purification on silica gel (EtOAc–hexanes, 1:30), 3b was obtained as a white powder; yield: 2.2 g (97%); mp 87–88 °C; [α]_D ²⁰ +61.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3341.7, 3060.3, 2923.8, 1645.0, 1509.5, 1502.7, 1436.0, 1211.6, 1093.3, 918.4, 701.9 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.17 (3 H, s), 2.69 (3 H, s), 4.62 (1 H, d, J = 8 Hz), 4.75 (1 H, d, J = 8 Hz), 7.10 (1 H, m), 7.19 (1 H, m), 7.2–7.28 (4 H, m), 7.41–7.45 (2 H, m), 7.53 (1 H, d, J = 8 Hz), 7.81 (1 H, d, J = 8 Hz), 8.56 (1 H, s).

¹³C NMR (100 MHz, CDCl₃): δ = 20.56, 56.7, 98.9, 124.9, 125.7, 125.9, 126.0, 126.3, 126.9, 127.0, 127.9, 128.2, 128.6, 129.0, 131.6, 131.9, 132.5, 133.3, 133.5, 135.8, 139.5, 150.9.

HRMS (ESI): m/z [M + H]⁺ calcd for C₂₃H₂₀IO₂ + H: 455.0503; found: 455.0502.

(R)-3-Iodo-2-methoxy-1-(2-phenylnaphthalen-1-yl)naphthalene (3c)

Compound 3a (517 mg, 1 mmol) was dissolved in a solution of ­EtOAc–MeOH–concd HCl (6 mL:6 mL:1 mL) and the solution was refluxed for 4 h. After evaporation of solvents and drying under vacuum, the crude product was dissolved in acetone (8 mL) under N₂. To the solution was added MeI (282 mg, 2 mmol) and K₂CO₃ (276 mg, 2 mmol) at r.t., and the mixture was heated at 40 °C for 12 h with stirring. After cooling to r.t., and removal of solvents, the residual oil was purified by column chromatography on silica gel (EtOAc–hexanes, 1:10) to give 3c as a white powder; yield: 476 mg (98%); mp 76–78 °C.

¹H NMR (400 MHz, CDCl₃): δ = 3.17 (3 H, s), 6.95–6.97 (3 H, m), 7.01–7.04 (2 H, m), 7.07–7.09 (1 H, m), 7.13–7.17 (2 H, m), 7.18–7.20 (1 H, m), 7.25–7.29 (1 H, m), 7.37–7.41 (1 H, m), 7.57–7.62 (2 H, m), 7.87 (1 H, d, J = 8 Hz), 7.95 (1 H, d, J = 8 Hz), 8.27 (1 H, s).

¹³C NMR (100 MHz, CDCl₃): δ = 60.6, 92.3, 125.4, 125.8, 126.3, 126.6, 126.64, 126.7, 126.9, 126.92, 127.5, 128.1, 128.3, 128.51, 128.54, 128.7, 130.98, 131.8, 132.6, 133.2, 135.7, 139.2, 140.5, 141.5, 154.1.

Bidentate Imidazolium Salts

(R)-N ¹-[3-(Methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (4a); Typical Procedure

To a mixture of Pd(OAc)₂ (22.5 mg, 0.1 mmol), BINAP (124.5 g, 0.2 mmol), and Cs₂CO₃ (652 mg, 2.0 mmol) was added a solution of 3a (516 mg, 1.0 mmol) and benzene-1,2-diamine (160 mg, 1.5 mmol) in 1,4-dioxane (15 mL) under N₂, and the reaction mixture was heated at 100 °C for 14 h with stirring. After cooling to r.t., and removal of solvents, the mixture was extracted with CH₂Cl₂ (3 × 20 mL). The combined organic extracts were washed with brine (20 mL) and dried (Na₂SO₄). Purification of the residual oil by column chromatography on silica gel (hexanes–EtOAc, 10:1) afforded 4a as a brown powder; yield: 451 mg (91%); mp 112 °C; [α]_D ²⁰ +141.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3468.2, 3054.7, 2955.8, 2853.8, 1733.4, 1616.1, 1592.7, 1502.6, 1452.8, 1425.0, 1244.9, 1069.9, 970.8, 747.1, 700.7 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 3.01 (3 H, s), 3.63 (2 H, s), 4.28 (1 H, d, J = 4 Hz), 4.51 (1 H, d, J = 4 Hz), 6.07 (1 H, s), 6.76–6.79 (2 H, m), 6.89 (1 H, s), 6.99–7.08 (5 H, m), 7.10–7.14 (4 H, m), 7.20 (1 H, s), 7.22–7.26 (1 H, m), 7.28–7.32 (1 H, m), 7.39–7.41 (1 H, d, J = 8 Hz), 7.44–7.48 (1 H, m), 7.51 (1 H, d, J = 8 Hz), 7.69 (1 H, d, J = 12 Hz), 7.93 (1 H, d, J = 8 Hz), 8.00 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 57.1, 98.9, 107.9, 116.2, 118.9, 123.1, 125.3, 125.9, 126.25, 126.3, 126.6, 126.63, 127.2, 127.4, 127.5, 128.07, 128.10, 128.4, 128.5, 129.9, 129.91, 161.5, 131.5, 131.8, 132.7, 133.5, 138.3, 140.4, 141.9, 142.5, 144.5.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₄H₂₉N₂O₂ + H: 497.2224; found: 497.2229.

(S)-N ¹-[3-(Methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (4b)

This compound was prepared from 3b (1.0 mmol, 454 mg) by the same procedure as described for the synthesis of 4a. After purification on silica gel (EtOAc–hexanes, 1:10), 4b was obtained as a white solid; yield: 407 mg (94%); mp 97 °C; [α]_D ²⁰ +81.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3411.3, 2941.1, 2243.2, 1669.4, 1039.8, 825.8, 762.4, 629.1 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.25 (3 H, s), 3.12 (3 H, s), 3.95 (2 H, s), 4.53–4.61 (2 H, m), 6.37 (1 H, s), 6.88–7.04 (4 H, m), 7.09 (1 H, s), 7.13–7.17 (1 H, m), 7.28–7.32 (2 H, m), 7.39 (1 H, d, J = 8 Hz), 7.43–7.45 (1 H, m), 7.56 (1 H, d, J = 8 Hz), 7.63 (1 H, d, J = 8 Hz), 7.91 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.7, 57.2, 99.1, 107.6, 116.3, 119.1, 122.9, 124.9, 125.5, 125.6, 125.9, 126.1, 126.2, 127.3, 127.5, 127.9, 128.2, 128.7, 131.9, 132.0, 132.3, 133.3, 135.5, 138.4, 142.5, 144.3.

HRMS (ESI): m/z [M + H]⁺ calcd for C₂₉H₂₇N₂O₂ + H: 435.2067; found: 435.2071.

(R)-N ¹-Mesityl-N ²-[3-(methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (5a); Typical Procedure

To a mixture of Pd(OAc)₂ (23 mg, 0.1 mmol), DPE-Phos (125 mg, 0.2 mmol), and Cs₂CO₃ (652 mg, 2.0 mmol) was added a solution of 4a (496 mg, 1.0 mmol) and 2-bromo-1,3,5-trimethylbenzene (300 mg, 1.5 mmol) in 1,4-dioxane (15 mL) under N₂, and the reaction mixture was heated at 110 °C for 17 h with stirring. After cooling to r.t., and removal of solvents, the mixture was extracted with CH₂Cl₂ (3 × 20 mL), and the combined organic extracts were washed with brine (20 mL) and dried (Na₂SO₄). Purification of the residual oil by column chromatography on silica gel (hexanes–­EtOAc, 10:1) afforded 5a as a brown powder; yield: 534 mg (87%); mp 137 °C; [α]_D ²⁰ +160.1 (c = 0.1, CH₂Cl₂).

IR (KBr): 3468.2, 3054.7, 2955.8, 2853.8, 1733.4, 1616.1, 1592.7, 1502.6, 1452.8, 1425.0, 1244.9, 1069.9, 970,8, 747.1, 700.7 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.06 (6 H, s), 2.29 (3 H, s), 3.04 (3 H, s), 4.30 (1 H, d, J = 8 Hz), 4.53 (1 H, d, J = 8 Hz), 4.74 (1 H, d, J = 8 Hz), 6.75–6.83 (2 H, m), 6.91–7.07 (9 H, m), 7.13 (1 H, d, J = 8 Hz), 7.18–7.29 (3 H, m), 7.33–7.35 (1 H, m), 7.44–7.54 (3 H, m), 7.66 (1 H, d, J = 8 Hz), 7.94 (1 H, d, J = 8 Hz), 8.01 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 18.3, 21.0, 57.1, 98.93, 112.1, 117.7, 123.1, 125.3, 125.8, 126.2, 126.3, 126.5, 126.6, 126.7, 127.2, 127.3, 128.0, 128.1, 128.4, 128.8, 129.0, 129.2, 131.7, 132.7, 135.4, 135.5, 136.0, 138.2, 141.8, 142.3, 144.4.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₃H₃₉N₂O₂ + H: 615.7814; found: 615.7814.

(S)-N ¹-Mesityl-N ²-[3-(methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (5b)

This compound was prepared from 4b (434 mg, 1.0 mmol) and 2-bromo-1,3,5-trimethylbenzene (300 mg, 1.5 mmol) by the procedure as described for the synthesis of 5a. After purification on silica gel (EtOAc–hexanes, 1:10), 5b was obtained as a white solid; yield: 425 mg (77%); mp 125 °C; [α]_D ²⁰ +134.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3409.1, 3011.9, 2938.8, 1755.3, 1560.0, 1534.2, 1473.1, 1446.9, 1371.2, 1250.4, 1061.4, 972.0, 749.1 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.09 (9 H, s), 2.13–2.20 (3 H, m), 2.99 (3 H, s), 4.43–4.50 (2 H, m), 5.52 (1 H, s), 6.24–6.26 (1 H, m), 6.42 (1 H, s), 6.73–6.74 (1 H, m), 6.84–6.89 (4 H, m), 6.92–6.96 (1 H, m), 7.10 (2 H, s), 7.18–7.32 (6 H, m), 7.40 (1 H, d, J = 8 Hz), 7.50 (1 H, d, J = 8 Hz), 7.77 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 18.4, 20.7, 21.0, 57.3, 99.2, 108.4, 112.4, 118.0, 125.5, 125.7, 126.17, 126.22, 126.3, 126.4, 128.0, 128.8, 129.3, 132.1, 132.4, 133.3, 135.4, 135.5, 135.6, 135.8, 138.4, 142.2, 144.5.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₈H₃₇N₂O₂ + H: 553.2850; found: 553.2841.

(R)-N ¹-(2,6-Diisopropylphenyl)-N ²-[3-(methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (5c)

This compound was prepared from 4a (1.0 mmol, 496 mg) and 2-bromo-1,3-diisopropylbenzene (361 mg, 1.5 mmol) by the procedure as described for the synthesis of 5a. After being purification on silica gel (EtOAc–hexanes, 1:10), 5c was obtained as a white solid; yield: 571 mg (87%); mp 131 °C; [α]_D ²⁰ +114.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3369.1, 2999.7, 2976.7, 1631.3, 1596.7, 1546.2, 1460.1, 1371.8, 1221.6, 751.6, 677.4 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 0.83 (3 H, d, J = 8 Hz), 1.02 (3 H, d, J = 8 Hz), 1.10–1.13 (6 H, m), 3.07 (3 H, s), 4.31 (1 H, d, J = 8 Hz), 4.53 (1 H, d, J = 8 Hz), 5.40 (1 H, s), 6.20 (1 H, s), 6.24 (1 H, d, J = 8 Hz), 6.73–6.77 (1 H, m), 6.89–6.98 (4 H, m), 7.00–7.06 (2 H, m), 7.09–7.13 (3 H, m), 7.17–7.21 (3 H, m), 7.26–7.33 (8 H, m), 7.38–7.40 (1 H, m), 7.46–7.50 (1 H, t, J = 8 Hz), 7.54 (1 H, d, J = 8 Hz), 7.67 (1 H, d, J = 8 Hz), 7.95 (1 H, d, J = 8 Hz), 8.02 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 23.1, 24.5, 28.2, 57.0, 98.9, 107.8, 112.2, 117.5, 123.0, 123.7, 125.2, 125.8, 126.2, 126.5, 126.6, 126.9, 127.0, 127.1, 127.3, 128.0, 128.4, 128.8, 131.8, 132.7, 133.4, 135.3, 140.3, 141.7, 147.4.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₆H₄₅N₂O₂ + H: 657.3476; found: 657.3476.

(S)-N ¹-(2,6-Diisopropylphenyl)-N ²-(3-(methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl)benzene-1,2-diamine (5d)

This compound was prepared from diamine 4b (1.0 mmol, 434 mg) and 2-bromo-1,3-diisopropylbenzene (361 mg, 1.5 mmol) by the same procedure as described for the synthesis of 5a. After purification on silica gel (EtOAc–hexanes, 1:10), 5d was obtained as a brown solid; yield: 487 mg (82%); mp 139 °C; [α]_D ²⁰ +172.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3379.9, 3035.4, 3001.1, 2926.7, 1561.9, 1523.3, 1455.6, 1421.1, 1251.1, 1194.1, 969.9, 815.6, 757.1, 696.0 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 0.96–1.01 (6 H, m), 1.14–1.16 (6 H, m), 2.21 (3 H, s), 3.10 (3 H, s), 4.51 (1 H, d, J = 8 Hz), 4.56 (1 H, d, J = 8 Hz), 6.33 (1 H, d, J = 8 Hz), 6.42 (1 H, s), 6.82 (1 H, t, J = 8 Hz), 6.95 (1 H, m), 6.98–7.00 (1 H, m), 7.05–7.10 (4 H, m), 7.19–7.20 (2 H, m), 7.24–7.29 (4 H, m), 7.38–7.40 (2 H, m), 7.50 (1 H, d, J = 8 Hz), 7.60 (1 H, d, J = 8 Hz), 7.87 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.6, 22.8, 23.1, 24.5, 57.1, 99.2, 107.9, 112.5, 117.7, 123.5, 123.8, 125.0, 125.5, 126.0, 126.2, 126.3, 127.1, 128.0, 128.7, 132.0, 132.4, 133.3, 135.4, 135.5, 139.0, 144.3, 144.4, 147.3, 150.0.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₁H₄₃N₂O₂ + H: 595.3319; found: 595.3319.

(R)-N ¹-(3-(Methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl)-N ²-phenylbenzene-1,2-diamine (5e)

This compound was prepared from diamine 4a (1.0 mmol, 496 mg) bromobenzene (234 mg, 1.5 mmol) by the same procedure as described for the synthesis of 5a. After being purification on silica gel (EtOAc–hexanes, 1:10), 5e was obtained as a white solid; yield: 434 mg (76%); mp 127 °C; [α]_D ²⁰ +124.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3379.7, 2998.9, 2956.7, 1731.3, 1541.2, 1470.1, 1368.9, 1226.7, 750.6, 698.4 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.93 (3 H, s), 4.24 (1 H, m), 4.44 (1 H, m), 5.70 (1 H, s), 6.29 (1 H, s), 6.89–6.91 (1 H, m), 6.95–6.99 (3 H, m), 7.04–7.14 (9 H, m), 7.20–7.36 (1 H, m), 7.46–7.50 (1 H, m), 7.55 (1 H, d, J = 8 Hz), 7.69 (1 H, d, J = 8 Hz), 7.94 (1 H, d, J = 8 Hz), 8.01 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 57.0, 98.9, 109.2, 117.9, 118.4, 120.9, 121.8, 123.1, 123.4, 124.3, 125.3, 125.8, 126.2, 126.4, 126.6, 127.0, 127.5, 128.0, 128.3, 128.4, 128.5, 128.9, 129.3, 131.3, 131.5, 132.1, 132.6, 133.4, 137.0, 137.3, 140.3, 141.8, 143.4, 145.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₀H₃₃N₂O₂ + H: 573.2537; found: 573.2541.

(S)-N ¹-[3-(Methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl]-N ²-phenylbenzene-1,2-diamine (5f)

This compound was prepared from diamine 4b (1.0 mmol, 434 mg) and bromobenzene (234 mg, 1.5 mmol) by the procedure described as for the synthesis of 5a. After purification on silica gel (EtOAc–hexanes, 1:10), 5f was obtained as a white solid; yield: 453 mg (89%); mp 109 °C; [α]_D ²⁰ +131.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3378.9, 3049.4, 2924.7, 1591.0, 1513.5, 1456.8, 1420.4, 1341.4, 1245.1, 1154.4, 970.9, 813.8, 747.3, 696.3 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.23 (3 H, s), 3.01 (3 H, s), 4.46 (1 H, d, J = 8 Hz), 4.51 (1 H, d, J = 8 Hz), 6.93–6.99 (2 H, m), 7.03–7.11 (5 H, m), 7.25–7.35 (5 H, m), 7.43–7.45 (3 H, m), 7.55 (1 H, d, J = 8 Hz), 7.63 (1 H, d, J = 8 Hz), 7.66 (1 H, d, J = 8 Hz), 7.90 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.6, 57.1, 99.3, 108.7, 117.9, 118.9, 120.9, 122.2, 122.8, 123.3, 124.4, 124.9, 125.6, 125.62, 126.1, 126.3, 126.34, 127.7, 127.9, 128.4, 128.7, 129.3, 131.8, 132.0, 132.1, 132.5, 133.2, 135.4, 137.5, 143.6, 144.9.

HRMS (ESI): m/z [M + H]⁺) calcd for C₃₅H₃₁N₂O₂ + H: 511.2380; found: 511.2385.

(S)-N ¹-(3,5-Di-tert-butylphenyl)-N ²-[3-(methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (5g)

This compound was prepared from diamine 4b (1.0 mmol, 434 mg) and 1-bromo-3,5-di-tert-butylbenzene (402 mg, 1.5 mmol) by the procedure described as for the synthesis of 5a. After purification on silica gel (EtOAc–hexanes, 1:10), 5g was obtained as a white solid; yield: 378 mg (61%); mp 113 °C; [α]_D ²⁰ +93.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3411.9, 2958.4, 1765.5, 1588.0, 1515.8, 1476.8, 1453.8, 1377.6, 1243.4, 1056.4, 970.2, 745.9 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 1.27 (18 H, s), 2.20 (3 H, s), 2.96 (3H, s), 4.43 (1 H, d, J = 8 Hz), 4.48 (1 H, d, J = 8 Hz), 5.95 (1 H, s), 6.59 (1 H, s), 6.93–6.97 (4 H, m), 7.01–7.02 (2 H, m), 7.10–7.12 (1 H, m), 7.24–7.27 (3 H, m), 7.36–7.41 (3 H, m), 7.47 (1 H, d, J = 8 Hz), 7.56–7.62 (2 H, m), 7.83 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.8, 31.6, 35.0, 57.2, 99.3, 108.7, 113.5, 115.8, 117.9, 121.3, 123.4, 123.5, 124.7, 125.1, 125.7, 125.73, 126.3, 126.4, 126.5, 127.8, 128.1, 128.5, 128.8, 131.6, 132.0, 132.1, 132.3, 133.4, 135.6, 137.9, 138.4, 142.5, 144.9, 152.0.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₃H₄₇N₂O₂ + H: 623.3632; found: 623.3632.

(S)-N ¹-[3-(Methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl]-N ²-(naphthalen-1-yl)-benzene-1,2-diamine (5h)

This compound was prepared from diamine 4b (1.0 mmol, 434 mg) and 1-bromonaphthalene (309 mg, 1.5 mmol) by the procedure described as for the synthesis of 5a. After purification on silica gel (EtOAc–hexanes, 1:10), 5h was obtained as a white solid; yield: 330 mg (59%); mp 141 °C; [α]_D ²⁰ +81.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3463.9, 3009.0, 2953.7, 2920.6, 2851.2, 2360.9, 2337.1, 1737.8, 1720.3, 1545.2, 1370.4, 1262.4, 1222.4, 750.2, 702.2 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.08 (3 H, s), 2.81 (3 H, s), 4.30 (1 H, d, J = 8 Hz), 4.37 (1 H, d, J = 8 Hz), 6.87–6.90 (1 H, m), 6.90–6.93 (2 H, m), 7.00–7.04 (2 H, m), 7.11 (1 H, s), 7.14–7.15 (2 H, m), 7.21 (1 H, s), 7.23 (1 H, s), 7.26–7.32 (3 H, m), 7.34 (1 H, d, J = 8 Hz), 7.38 (1 H, d, J = 8 Hz), 7.42 (1 H, d, J = 8 Hz), 7.46 (1 H, d, J = 8 Hz), 7.56 (1 H, d, J = 8 Hz), 7.71 (1 H, d, J = 8 Hz), 7.75 (2 H, d, J = 8 Hz), 7.81 (1 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.7, 57.1, 99.2, 108.7, 116.0, 117.9, 121.2, 121.9, 122.9, 123.4, 124.2, 125.0, 125.2, 125.7, 126.1, 126.3, 126.4, 127.8, 127.97, 128.0, 128.5, 128.6, 128.7, 130.9, 131.8, 132.0, 132.2, 133.3, 134.7, 135.5, 137.9, 138.8, 139.4, 144.7.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₉H₃₃N₂O₂ + H: 561.2537; found: 561.2536.

Benzimidazolium Salts 6; General Procedure

The diamine 5 (0.5 mmol) was dissolved in a mixture of EtOAc–MeOH–concd HCl (6 mL:6 mL:1 mL), and the solution was stirred at 70 °C overnight. Then, the solvent was removed under reduced pressure to give a yellow solid. The yellow solid was dissolved in HC(OEt)₃ (5 mL) under N₂ and the mixture was stirred at 80 °C for 6 h. After cooling to r.t., the mixture was filtered and washed with Et₂O (10 mL). The solid was dried under vacuum to afford the benzimidazolium chloride 6.

Benzimidazolium Salt 6a

Yield: 185 mg (60%); white solid; mp 217 °C; [α]_D ²⁰ +130.9 (c = 0.1, CH₂Cl₂).

IR (KBr): 3393.5, 3014.3, 1603.4, 1597.7, 1509.8, 1446.2, 1161.9, 11408, 1067.7, 814.9, 753.7 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.06–2.13 (6 H, m), 2.41 (3 H, m), 6.80 (1 H, m), 7.06 (1 H, d, J = 8 Hz), 7.22–7.29 (9 H, m), 7.42–7.43 (3 H, m), 7.49–7.51 (1 H, m), 7.54–7.58 (1 H, m), 7.69–7.71 (3 H, m), 8.03 (1 H, m), 8.13 (1 H, d, J = 8 Hz), 8.21 (1 H, d, J = 8 Hz), 8.55 (1 H, s), 10.65 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 17.7, 20.7, 113.4, 114.2, 122.3, 125.8, 126.8, 127.7, 127.9, 128.1, 128.3, 128.4, 128.6, 128.7, 129.8, 135.3, 135.4, 140.5, 140.9, 141.5, 144.2.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₂H₃₃N₂O + H: 581.2587; found: 581.2594.

Benzimidazolium Salt 6b

Yield: 205 mg (74%); white solid; mp 241–243 °C; [α]_D ²⁰ +116.6 (c = 0.1, CH₂Cl₂).

IR (KBr): 3434.9, 2996.2, 1634.0, 1554.3, 1252.1, 1126.0, 1051.9, 1026.4, 825.3, 761.1, 625.7cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.07 (9 H, s), 2.42 (3 H, s), 6.85 (1 H, s), 7.02–7.28 (2 H, m), 7.39–7.58 (6 H, m), 7.74 (2 H, s), 7.98–8.11 (3 H, m), 8.67 (1 H, s), 10.60 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 17.1, 20.0, 20.7, 58.9, 113.3, 114.4, 122.3, 124.1, 125.0, 126.2, 127.8, 127.9, 128.1, 128.5, 128.6, 128.7, 128.9, 129.5, 129.8, 131.9, 134.1, 135.3, 135.32, 135.5, 141.0.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₇H₃₁N₂O + H: 519.2431; found: 519.2430.

Benzimidazolium Salt 6c

Yield: 215 mg (65%); white solid; mp 273 °C; [α]_D ²⁰ +188.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3419.7, 3011.1, 2968.7, 2912.7, 1637.3, 1601.9, 1544.2, 1470.1, 1268.3, 1221.9, 763.6, 678.4 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 1.06–1.22 (14 H, m), 7.01 (2 H, s), 7.22–7.31 (6 H, m), 7.41 (3 H, s), 7.56–7.61 (4 H, m), 7.76 (4 H, m), 8.04–8.23 (3 H, m), 8.56 (1 H, s), 9.90 (1 H, s), 10.74 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 24.0, 24.1, 24.7, 24.9, 28.6, 113.8, 114.8, 122.4, 122.6, 125.1, 125.6, 126.3, 126.5, 127.3, 127.9, 128.2, 128.6, 128.9, 129.1, 129.5, 129.8, 132.4, 132.7, 132.9, 133.0, 133.2, 141.2, 141.9, 144.8, 146.7, 146.8.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₅H₃₉N₂O + H: 623.3057; found: 623.3051.

Benzimidazolium Salt 6d

Yield: 191 mg (64%); white solid; mp 237 °C; [α]_D ²⁰ +113.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3424.2, 2253.2, 2126.6, 1651.3, 1546.2, 1051.8, 1026.7, 1006.8, 824.3, 762.4, 627.7 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 0.83–0.86 (7 H, m), 1.06–1.10 (7 H, m), 2.19 (3 H, s), 6.90 (1 H, d, J = 8 Hz), 7.22 (1 H, d, J = 8 Hz), 7.31–7.32 (1 H, m), 7.39–7.41 (1 H, m), 7.44–7.53 (2 H, m), 7.56–7.65 (4 H, m), 7.76–7.83 (2 H, m), 7.86 (1 H, m), 8.01–8.07 (3 H, m), 8.20 (1 H, m), 8.78 (1 H, s), 10.90 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 13.8, 20.1, 21.7, 23.5, 24.3, 28.1, 33.5, 113.2, 114.6, 122.5, 123.0, 124.1, 124.7, 124.9, 125.0, 125.1, 126.3, 127.4, 127.5, 127.6, 128.1, 128.3, 128.5, 128.9, 130.0, 131.8, 132.0, 132.2, 132.5, 132.7, 133.9, 135.7, 145.0, 146.2, 146.3.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₀H₃₇N₂O + H: 561.2900; found: 561.2892.

Benzimidazolium Salt 6e

Yield: 216 mg (75%); white solid; mp 271 °C; [α]_D ²⁰ +161.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3451.7, 2960.3, 2923.8, 2855.0, 1625.0, 1505.9, 1562.7, 1430.6, 1261.1, 1096.3, 1018.4, 801.9 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 6.65 (1 H, s), 7.08 (1 H, d, J = 8 Hz), 7.24–7.28 (6 H, m), 7.40–7.43 (3 H, m), 7.55–7.58 (1 H, m), 7.66–7.81 (6 H, m), 7.89 (1 H, d, J = 8 Hz), 7.98 (3 H, m), 8.11 (1 H, d, J = 8 Hz), 8.19 (1 H, d, J = 8 Hz), 8.49 (1 H, s), 9.85 (1 H, s), 10.73 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 113.7, 113.8, 122.3, 122.4, 124.6, 124.7, 125.3, 125.8, 125.9, 126.77, 126.8, 127.3, 127.5, 127.7, 128.3, 128.5, 128.67, 12.8.71, 129.8, 130.4, 130.7, 130.9, 131.1, 132.3, 132.6, 133.0, 134.9, 140.4, 141.7, 143.7, 147.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₉H₂₇N₂O + H: 539.2118; found: 539.2117.

Benzimidazolium Salt 6f

Yield: 197 mg (77%); white solid; mp 219 °C; [α]_D ²⁰ +83.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3423.3, 2253.2, 1659.2, 1026.8, 824.8, 762.6, 627.8 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.19 (3 H, s), 6.92 (1 H, d, J = 8 Hz), 7.22 (1 H, d, J = 8 Hz), 7.33–7.50 (5 H, m), 7.62 (1 H, d, J = 8 Hz), 7.73–7.82 (6 H, m), 7.95–8.02 (5 H, m), 8.11 (1 H, d, J = 8 Hz), 8.63 (1 H, s), 9.77 (1 H, s), 10.78 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.4, 113.7, 114.3, 122.4, 122.8, 124.2, 124.8, 124.9, 125.0, 125.3, 126.3, 127.5, 127.6, 128.1, 128.2, 128.6, 128.8, 128.9, 130.5, 130.7, 131.0, 131.9, 132.2, 132.6, 133.0, 134.1, 135.2, 144.0, 146.8.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₄H₂₅N₂O + H: 477.1961: found: 477.1954.

Benzimidazolium Salt 6g

Yield: 262 mg (84%); white solid; mp 249 °C; [α]_D ²⁰ +143.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3446.9, 2964.1, 2252.9, 2126, 1654.0, 1551.1, 1051.9, 1027.5, 1005.2, 824.3, 762.6, 625.7 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 1.42 (18 H, s), 2.20 (3 H, s), 6.93 (1 H, d, J = 8 Hz), 7.23 (1 H, d, J = 8 Hz), 7.36–7.50 (4 H, m), 7.63 (1 H, d, J = 8 Hz), 7.72 (1 H, s), 7.77–7.83 (5 H, m), 7.93 (1 H, s), 8.03 (2 H, m), 8.13 (1 H, d, J = 8 Hz), 8.64 (1 H, s), 9.83 (1 H, s), 10.80 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.0, 31.0, 35.0, 113.7, 114.3, 119.6, 122.5, 122.9, 124.2, 124.8, 124.9, 125.1, 126.3, 127.5, 127.6, 128.1, 128.2, 128.5, 128.8, 128.9, 130.5, 131.1, 131.9, 132.2, 132.6, 132.8, 134.1, 135.2, 144.1, 146.9, 153.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₂H₄₁N₂O + H: 589.3213; found: 589.3210.

Benzimidazolium Salt 6h

Yield: 143 mg (51%); white solid; mp 261 °C; [α]_D ²⁰ +163.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3478.8, 3053.9, 2392.0, 2348.6, 2288.2, 1621.4, 1544.80, 1487.7, 1380.7, 1359.8, 1244.9, 806.0, 748.1, 702.0 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.16 (3H, s), 6.89 (1 H, s), 7.18–8.37 (21 H, m), 8.72 (1 H, s), 9.88 (1 H, s), 10.81 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.1, 104.2, 113.7, 114.4, 125.1, 127.9, 128.2, 128.7, 128.9, 132.5, 144.7, 145.0, 146.6.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₈H₂₇N₂O + H: 527.2118; found: 527.2117.

Benzimidazoles 7a and 7b; General Procedure

The diamine 4 (1 mmol) and TsOH (17 mg, 0.1 mmol) were dissolved in HC(OEt)₃ (5 mL) and the solution was refluxed at 100 °C for 24 h. After cooling to r.t., and removal of solvents, the residue was purified by column chromatography on silica gel (EtOAc as eluent) to afford the desired product.

1-[(2S,4R)-3-(Methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]-1H-benzoimidazole (7a)

Yield: 458 mg (91%); white solid; mp 107 °C; [α]_D ²⁰ + 78.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3448.1, 3056.2, 2957.2, 2926.4, 2855.4, 1713.3, 1649.2, 1599.0, 1495.0, 1460.8, 1375.3, 1260.7, 1243.4, 1062.3, 1034.3, 824.3, 750.7, 700.9, 659.4 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.14 (3 H, s), 3.99 (1 H, d, J = 8 Hz), 4.10 (1 H, d, J = 8 Hz), 6.49 (1 H, s), 7.13–7.15 (2 H, d, J = 8 Hz), 7.18–7.24 (3 H, m), 7.27–7.32 (2 H, m), 7.36–7.40 (1 H, m), 7.43–7.47 (2 H, d, J = 8 Hz), 7.50–7.58 (3 H, m), 7.73 (1 H, d, J = 8 Hz), 7.82 (1 H, d, J = 8 Hz), 7.90–8.01 (4 H, m), 8.08 (1 H, m).

¹³C NMR (100 MHz, CDCl₃): δ = 55.8, 98.5, 111.6, 119.9, 122.5, 123.4, 125.6, 126.1, 126.4, 126.7, 126.74, 126.9, 127.7, 127.7, 128.2, 128.4, 128.9, 129.1, 129.4, 130.1, 130.3, 130.8, 132.8, 133.1, 134.6, 141.2, 142.1, 143.1, 143.1, 147.8.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₅H₂₇N₂O₂ + H: 507.2067; found: 507.2067.

1-[(2S,4S)-3-(Methoxymethoxy)-4-(2-methylnaphthalen-1-yl)naphthalen-2-yl)-1H-benzo[d]imidazole (7b)

Yield: 429 mg (97%); white solid; mp 101 °C; [α]_D ²⁰ +125.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3444.2, 3054.1, 2956.6, 2926.0, 2856.3, 1613.4, 1596.2, 1491.5, 1435.8, 1286.7, 1268.8, 1241.2, 1157.5, 954.5, 917.9, 781.2, 744.5 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.13 (3 H, s), 2.18 (3 H, s), 4.04 (1 H, d, J = 8 Hz), 4.08 (1 H, d, J = 8 Hz), 7.10 (1 H, d, J = 8 Hz), 7.19–7.26 (5 H, m), 7.30–7.32 (1 H, m), 7.37–7.44 (3 H, m), 7.78–7.84 (4 H, m), 7.96 (1 H, s), 8.19 (1 H, s).

¹³C NMR (100 MHz, CDCl₃): δ = 20.7, 56.1, 98.7, 111.1, 120.4, 122.7, 123.7, 125.1, 125.8, 126.1, 126.37, 126.41, 126.5, 126.7, 128.1, 128.11, 128.4, 128.7, 129.4, 130.7, 130.9, 131.0, 132.1, 133.1, 113.2, 134.7, 135.6, 143.4, 143.7, 147.9.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₀H₂₅N₂O₂ + H: 445.1911; found: 445.1915.

Benzimidazolium Salts 6i–l; General Procedure

A mixture of benzimidazole 7 (0.5 mmol) and the respective halide (1 mmol) was dissolved in MeCN or 1,4-dioxane (1 mL) and the solution was refluxed in a Schlenck tube at 100 °C for 24 h. After cooling to r.t., and removal of solvents, the residue was purified by column chromatography on silica gel (CH₂Cl₂–MeOH, 10:1) to afford the desired product.

Benzimidazolium Salt 6i

Yield: 214 mg (71%); white solid; mp 167 °C; [α]_D ²⁰ +131.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3455.5, 3146.2, 3053.7, 2955.4, 2923.6, 2391.7, 2283.7, 1618.3, 1565.3, 1489.1, 1461.1, 1375.5, 1261.1, 960.9, 743.9, 702.3 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 4.18 (3 H, s), 6.28–6.30 (1 H, m), 7.08–7.10 (2 H, m), 7.13–7.17 (2 H, m), 7.2–7.27 (2 H, m), 7.32 (1 H, m), 7.36–7.41 (3 H, m), 7.44–7.46 (2 H, m), 7.52 (1 H, m), 7.59–7.61 (1 H, m), 7.64–7.68 (2 H, m), 7.94–7.96 (2 H, m), 8.05–8.08 (1 H, m), 8.44 (1 H, s), 10.27 (1 H, s).

¹³C NMR (100 MHz, CDCl₃): δ = 26.9, 112.3, 113.9, 123.8, 125.7, 126.3, 126.4, 126.5, 126.7, 127.2, 127.6, 127.9, 128.8, 131.2, 131.8, 132.6, 133.2, 135.1, 140.3, 141.9.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₄H₂₅N₂O + H: 477.1961; found: 477.1962.

Benzimidazolium Salt 6j

Yield: 176 mg (54%); white solid; mp 203 °C; [α]_D ²⁰ +137.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3445.8, 3055.3, 2959.6, 2926.1, 1795.6, 1622.5, 1556.3, 1498.6, 1448.5, 1405.9, 1376.3, 1358.1, 1124.9, 825.2, 748.5, 700.1 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 5.93 (2 H, s), 6.69–6.71 (1 H, m), 7.02–7.04 (1 H, m), 7.20–7.29 (6 H, m), 7.55–7.60 (1 H, m), 7.62–7.64 (2 H, m), 7.66–7.68 (2 H, m), 7.70–7.73 (1 H, m), 7.97 (1 H, m), 8.06 (1 H, m), 8.11 (1 H, d, J = 8 Hz), 8.21 (1 H, d, J = 8 Hz), 8.43 (1 H, s), 10.49 (1 H, s).

¹³CNMR (100 MHz, CDCl₃): δ = 50.3, 113.7, 114.1, 121.8, 122.2, 124.6, 124.7, 125.8, 126.0, 126.8, 127.2, 127.7, 128.1, 128.3, 128.5, 128.6, 128.8, 128.9, 129.5, 160.1, 132.2, 132.4, 132.7, 133.6, 134.8, 140.5, 141.5, 134.5, 146.9.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₀H₂₉N₂O + H: 553.2274; found: 553.2282.

Benzimidazolium Salt 6k

Yield: 211 mg (78%); white solid; mp 147 °C; [α]_D ²⁰ +149.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3404.7, 3142.4, 3050.7, 2954.8, 2925.6, 2856.5, 1674.1, 1617.1, 1565.1, 1489.5, 1462.9, 1437.8, 1353.9, 1259.1, 981.6, 958.4, 817.6, 745.6, 697.8 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.05 (3 H, s), 3.22 (3 H, s), 4.18 (1 H, s), 6.76–6.81 (2 H, m), 6.98–7.01 (1 H, m), 7.09–7.16 (2 H, m), 7.29 (2 H, s), 7.45–7.51 (4 H, m), 7.58 (1 H, d, J = 8 Hz), 7.69 (1 H, d, J = 8 Hz), 7.74 (1 H, m), 7.79–7.81 (2 H, m), 9.76 (1 H, s).

¹³C NMR (100 MHz CDCl₃): δ = 20.3, 32.3, 112.2, 113.8, 123.4, 124.4, 125.6, 126.0, 126.1, 126.4, 126.5, 126.6, 126.8, 127.4, 128.1, 129.1, 131.3, 131.6, 131.9, 133.5, 135.1, 135.7.

HRMS (ESI): m/z [M + H]⁺ calcd for C₂₉H₂₃N₂O + H: 415.1805; found: 415.1804.

Benzimidazolium Salt 6l

Yield: 202 mg (64%); white solid; mp 155 °C; [α]_D ²⁰ +133.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3424.1, 3121.4, 3000.7, 2959.6, 2927.6, 1671.1, 1617.9, 1562.1, 1479.6, 1463.0, 1352.8, 986.4, 958.8, 813.0, 745.1 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.14 (3 H, s), 5.76 (2 H, s), 7.06–7.08 (2 H, m), 7.25–7.52 (15 H, m), 7.89–7.97 (3 H, m), 8.17 (1 H, s), 10.34 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.5, 51.6, 113.9, 114.0, 122.8, 123.6, 124.9, 124.92, 125.3, 125.5, 126.7, 126.9, 127.1, 127.4, 127.7, 128.2, 128.4, 128.6, 128.7, 128.8, 129.1, 129.2, 130.8, 132.2, 132.4, 132.7, 132.8, 134.4, 136.6, 143.4.

HRMS (ESI): m/z [M + H]⁺ calcd for C₃₅H₂₇N₂O + H: 491.2118; found: 491.2109.

Tridentate Imidazolium Salts; General Procedure

Diamines 8a–c were synthesized by the similar procedure as for the synthesis of 4; the only change was the 3:1 ratio of halide 3 to 1,2-diaminobenzene (0.5 mmol). Benzimidazolium salts 9a–c were synthesized as above following the procedure for 6a–h (0.25 mmol scale).

N ¹-[(R)-3-(Methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]-N ²-[3-(methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (8a)

Eluent: hexanes–EtOAc (10:1); yield: 348 mg (79%); white solid; mp 109–112 °C; [α]_D ²⁰ +136.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3420, 3055, 1653, 1636, 1559, 1541, 1521, 1507, 1489, 1473,1271, 1261, 764, 754 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.71 (6 H, s), 4.17 (2 H, d, J = 8 Hz), 4.36 (2 H, d, J = 8 Hz), 6.47 (2 H, s), 6.93–6.96 (6 H, m), 7.02–7.06 (4 H, m), 7.09–7.13 (6 H, m), 7.19–7.21 (3 H, m), 7.23–7.27 (5 H, m), 7.34 (2 H, s), 7.40–7.44 (2 H, m), 7.52–7.54 (2 H, d, J = 8 Hz), 7.64 (2 H, d, J = 8 Hz), 7.90 (2 H, d, J = 8 Hz), 7.98 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 56.7, 98.6, 110.8, 121.2, 123.3, 123.7, 125.3, 125.8, 126.3, 126.4, 126.5, 126.6, 127.1, 127.5, 128.0, 128.3, 128.5, 128.6, 128.9, 129.6, 131.5, 132.7, 133.4, 134.8, 136.9, 140.2, 141.8, 145.5.

HRMS (ESI): m/z [M + H]⁺ calcd for C₆₂H₄₉N₂O₄ + H: 885.3687; found: 885.3688.

N ¹-[(R)-3-(Methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]-N ²-[3-(methoxymethoxy)-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (8b)

Eluent: hexanes–EtOAc (10:1); yield: 307 mg (81%); white solid; mp 142 °C; [α]_D ²⁰ +171.0 (c =0.1, CH₂Cl₂).

IR (KBr): 3415.8, 3055.5, 2841.5, 1611.8, 1570.2, 1450.5, 1147.7, 1080.8, 961.2, 802.2, 741.4 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.15 (6 H, s), 2.93 (6 H, s), 4.47 (2 H, d, J = 4 Hz), 4.53 (2 H, d, J = 4 Hz), 6.96 (2 H, s), 7.02–7.10 (4 H, m), 7.16–7.20 (2 H, m), 7.26–7.35 (8 H, m), 7.41–7.45 (2 H, m), 7.53 (2 H, d, J = 8 Hz), 7.67 (2 H, m), 7.80 (2 H, s), 7.92 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 20.5, 56.9, 98.8, 108.9, 122.6, 123.5, 124.1, 124.9, 125.6, 126.2, 126.23, 126.4, 127.9, 127.95, 128.6, 128.7, 132.0, 132.03, 132.12, 133.4, 134.9, 135.5, 137.3, 144.7.

HRMS (ESI): m/z [M + H]⁺ calcd for C₅₂H₄₅N₂O₄ + H: 761.3374; found: 761.3378.

N ¹-[(R)-3-Methoxy-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]-N ²-[3-methoxy-4-(2-phenylnaphthalen-1-yl)naphthalen-2-yl]benzene-1,2-diamine (8c)

Eluent: hexanes–EtOAc (10:1); yield: 343 mg (83%); white solid; mp 122 °C; [α]_D ²⁰ +142.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3456.5, 3054.9, 2932.4, 2361.0, 2337.7, 1737.1, 1713.9, 1622.5, 1563.2, 1494.3, 1453.4, 1390.2, 1352.7, 1231.8, 1017.7, 825.1, 753.4, 701.1 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.85 (6 H, s), 6.22 (2 H, s), 6.75–6.77 (6 H, m), 6.94–7.02 (5 H, m), 7.05–7.08 (4 H, m), 7.12 (2 H, m), 7.15 (3 H, m), 7.20 (2 H, m), 7.33–7.35 (4 H, m), 7.41 (1 H, s), 7.43 (1 H, s), 7.56 (1 H, s), 7.58 (1 H, s), 7.84 (2 H, d, J = 8 Hz), 7.93 (2 H, d, J = 8 Hz).

¹³C NMR (100 MHz, CDCl₃): δ = 59.9, 108.8, 122.1, 123.4, 123.8, 125.1, 125.7, 126.0, 126.3, 126.4, 126.5, 126.7, 127.4, 127.5, 127.9, 128.3, 128.6, 128.7, 129.4, 131.2, 132.6, 133.4, 134.5, 136.5, 140.1, 141.9, 147.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₆₀H₄₅N₂O₂ + H: 825.3476; found: 825.3482.

Benzimidazolium Salt 9a

Eluent: CH₂Cl₂–MeOH (10:1); yield: 133 mg (63%); white solid; mp 321 °C; [α]_D ²⁰ +191.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3473.3, 2955.7, 2923.7, 2852.7, 1623.3, 1495.4, 1462.8, 1261.8, 1154.3, 982.9, 952.5, 750.1, 700.9 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 6.73 (2 H, s), 7.06 (2 H, d, J = 4 Hz), 7.24–7.33 (14 H, m), 7.44 (8 H, s), 7.57–7.60 (2 H, m), 7.67–7.73 (2 H, m), 7.99 (2 H, m), 8.13 (2 H, d, J = 8 Hz), 8.21 (2 H, d, J = 8 Hz), 8.44 (2 H, s), 9.74 (2 H, s), 10.79 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 113.9, 122.0, 122.2, 123.9, 124.6, 124.7, 125.8, 126.0, 126.8, 126.9, 127.2, 127.7, 128.1, 128.4, 128.6, 128.7, 128.9, 129.5, 129.6, 131.7, 132.4, 132.7, 134.9, 140.5, 141.5, 147.0.

HRMS (ESI): m/z [M + H]⁺ calcd for C₅₉H₃₉N₂O₂ + H: 807.3006; found: 807.3011.

Benzimidazolium Salt 9b

Eluent: CH₂Cl₂–MeOH (10:1); yield: 130 mg (72%); white solid; mp 312 °C; [α]_D ²⁰ +241.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3448.8, 2924.3, 1644.4, 1549.4, 1503.8, 1484.8, 1269.6, 1025.3, 1000.5, 814.6, 748.2 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.19 (6 H, s), 6.90 (2 H, d, J = 8 Hz), 7.20 (2 H, d, J = 8 Hz), 7.36 (2 H, m), 7.43–7.51 (6 H, m), 7.63 (2 H, d, J = 8 Hz), 7.81 (4 H, s), 8.01–8.05 (4 H, m), 8.14 (2 H, d, J = 8 Hz), 8.64 (2 H, s), 9.71 (2 H, s), 10.88 (1 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.2, 114.3, 122.0, 122.7, 124.2, 124.8, 125.0, 126.4, 127.4, 127.5, 128.0, 128.2, 128.6, 128.8, 128.9, 130.2, 134.0, 132.6, 134.1, 135.4, 146.7.

HRMS (ESI): m/z [M + H]⁺ calcd for C₄₉H₃₅N₂O₂ + H: 683.2693; found: 683.2690.

Benzimidazolium Salt 9c

Eluent: CH₂Cl₂–MeOH (10:1); yield: 127 mg (59%); white solid; mp 301 °C; [α]_D ²⁰ +196.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3333.0, 3306.3, 3054.6, 3029.1, 2361.3, 2337.5, 1740.4, 1545.5, 1488.3, 1356.0, 1219.3, 1088.7, 1003.5, 827.3, 731.8, 701.6 cm^–1.

¹H NMR (400 MHz, CDCl₃): δ = 2.91 (6 H, s), 7.09–7.11 (4 H, m), 7.21–7.33 (1 H, m), 7.45–7.47 (2 H, m), 7.57–7.61 (6 H, m), 7.62–7.64 (3 H, m), 7.72 (2 H, d, J = 8 Hz), 8.13–8.15 (4 H, m), 8.24 (2 H, d, J = 8 Hz), 8.64 (2 H, s), 10.72 (1 H, s).

¹³C NMR (100 MHz, CDCl₃): δ = 60.9, 113.99, 125.1, 125.6, 125.8, 126.21, 126.6, 126.9, 127.2, 127.4, 127.8, 128.2, 128.5, 128.7, 128.8, 128.96, 129.01, 129.2, 129.3, 129.5, 131.1, 132.1, 132.4, 135.0, 140.1, 141.2, 149.1.

HRMS (ESI): m/z [M + H]⁺ calcd for C₆₁H₄₃N₂O₂ + H: 835.3319; found: 835.3319.

Tetradentate Imidazolium Salts

Benzimidazolium Salt 10b; Typical Procedure

Benzimidazole 7b (102 mg, 0.23 mmol) and 1,3-bis(bromomethyl)benzene (607 mg, 2.3 mmol) were dissolved in 1,4-dioxane (1.0 mL), and the solution was refluxed at 100 °C for 24 h. After cooling to r.t., and removal of solvents, the residue was dissolved in CH₂Cl₂–MeOH–concd HCl (3 mL:3 mL:1 mL), and allowed to react at r.t. for 4 h. The solution was added to n-pentane (20 mL), and the precipitated solid was filtered, and dried, affording a white solid. The resulting white solid and 7b (222 mg, 0.5 mmol) were dissolved in 1,4-dioxane (1.0 mL) and the mixture was refluxed at 100 °C for 24 h. After cooling to r.t., and removal of solvents, the mixture was dissolved in CH₂Cl₂–MeOH–concd HCl (3 mL:3 mL:1 mL). The solution was added to n-pentane (20 mL) and the precipitated solid was filtered, and dried affording the desired product 10b as a white solid; yield: 103 mg (46%); mp 367 °C; [α] _D ²⁰ +248.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3500.0, 3051.4, 2956.0, 2924.1, 2855.8, 1727.8, 1619.9, 1555.9, 1502.9, 1483.4, 1263.6, 1205.5, 814.9, 746.9, 698.4 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.16 (6 H, s), 6.00 (4 H, s), 6.88 (2 H, d, J = 8 Hz), 7.18 (2 H, d, J = 8 Hz), 7.3–7.34 (2 H, m), 7.40–7.52 (6 H, m), 7.53 (1 H, m), 7.61–7.69 (1 H, m), 8.00–8.06 (8 H, m), 8.14 (1 H, s), 8.60 (2 H, s), 9.57 (2 H, s), 10.59 (2 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 19.9, 50.1, 66.3, 114.1, 122.1, 122.8, 127.5, 128.9, 130.5, 132.2, 134.4, 143.8, 146.4.

HRMS (ESI): m/z [M + H]⁺ calcd for C₆₄H₄₈N₄O₂₂ + H: 904.3766; found: 904.3766.

Benzimidazolium Salt 10d

Yield: 195 mg (99%); white solid; mp 374 °C; [α]_D ²⁰ +164.0 (c = 0.1, CH₂Cl₂).

IR (KBr): 3457.0, 1673.1, 1559.9, 1507.2, 1458.2, 1275.5, 1262.2, 764.0, 750.8, 705.3 cm^–1.

¹H NMR (400 MHz, DMSO-d ₆): δ = 2.15 (6 H, s), 5.95 (4 H, s), 6.86 (2 H, d, J = 8 Hz), 7.16 (2 H, d, J = 8 Hz), 7.32 (2 H, m), 7.41–7.49 (7 H, m), 7.61 (1 H, s), 7.63 (1 H, s), 7.71 (10 H, m), 8.00–8.03 (4 H, m), 8.06–8.08 (4 H, m), 8.54 (2 H, s), 9.53 (2 H, s), 10.52 (2 H, s).

¹³C NMR (100 MHz, DMSO-d ₆): δ = 20.0, 114.0, 114.2, 122.7, 125.0, 126.3, 128.9, 129.0, 130.6, 143.9, 146.3.

HRMS (ESI): m/z [M + H]⁺ calcd for C₆₄H₄₈N₄O₂₂ + H: 904.3766; found: 904.3771.

Acknowledgment

We are grateful to the NNSFC (21172077, 21372086), the Program for New Century Excellent Talents in University (NCET-10-0403), The National Basic Research Program of China (973) (2011CB808600), the Changjiang Scholars and Innovation Team Project of Ministry of Education, SRF for ROCS, State Education Ministry, Guangdong NSF (1035106410 1000000), and the Fundamental Research Funds for the Central Universities, SCUT (2012ZZ0038) for supporting this work.

• References

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  Search in Google Scholar
• 1c Bourissou D, Guerret O, Gabbai FP, Bertrand G. Chem. Rev. 2000; 100: 39
  Search in Google Scholar
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• 1h Hahn FE, Jahnke MC. Angew. Chem. Int. Ed. 2008; 47: 3122
  Search in Google Scholar
• 1i Zeitler K. Angew. Chem. Int. Ed. 2005; 44: 7506
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  CrossrefSearch in Google Scholar
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  CrossrefSearch in Google Scholar
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  Search in Google Scholar
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  Search in Google Scholar
• 6c Díez-Gonzalez S, Marion N, Nolan SP. Chem. Rev. 2009; 109: 3612
  CrossrefPubMedSearch in Google Scholar
• 7a Muniz K. Adv. Synth. Catal. 2004; 346: 1425
  CrossrefSearch in Google Scholar
• 7b Muehlhofer M, Strassner T, Herrmann WA. Angew. Chem. Int. Ed. 2002; 41: 1745
  Search in Google Scholar
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  CrossrefPubMedSearch in Google Scholar
• 8b Romao CC, Kühn FE, Herrmann WA. Chem. Rev. 1997; 97: 3197
  CrossrefPubMedSearch in Google Scholar
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  Search in Google Scholar
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  CrossrefPubMedSearch in Google Scholar

• Supplementary Material