Introduction

Organosilicon chemistry can provide a wealth of chemical and biological diversity for drug discovery [1]. Silicon-containing analogs are generally more lipophilic than their carbon analogs. Lipophilicity can provide several physiological benefits, including an increase bioavailability and improved tissue and cell penetration. Therefore, incorporating organosilicon moieties is a strategy used to augment biological activity and reduce toxicity in a bid to enhance the therapeutic value of new drugs [2, 3]. Vinylsilanes, especially 2-aryl-1,1-bis(silyl)alkenes, are useful reagents in organic and organometallic synthesis, because of the presence of \(\hbox {C}(\hbox {sp}^{2})\hbox {-Si}\) bonds that undergo numerous transformations. Their use as precursors for the preparation of ketones and isoxazoline derivatives, as well as variety of organosilicon intermediates such as acylsilanes, epoxysilanes, 1-halosilanes, silylenol ethers, (E)-alkenylsilanes, and silylenolacetates, generates interest for their synthesis [4–9].

Cyclizations via one-pot multi-component coupling reactions (MCRs) [10] are great conduits for the preparation of heterocyclic compounds. Highly substituted imidazoles have emerged as an integral part of many biological systems (viz., histidine, histamine, and biotin). They have also been found valuable as fungicides, herbicides, plant growth regulators, tranquilizer, antitumor, anti-inflammatory, anticonvulsant, antiarthritic, antiallergic, analgesic, anti-HIV, and antibacterial agents [11–17]. All of this has generated high interest from synthetic organic/medicinal chemists to develop synthetic methodologies to access this heterocyclic scaffold exemplified by the strategies shown in Fig. 1. The reported synthesis of 1,2,4,5 tetrasubstituted imidazoles involves the reaction of a 1,2-dicarbonyl 1 \(^{\prime }\) a, \(\upalpha \)- hydroxyl 2 \(^{\prime }\) a/acetoxy 1 \(^{\prime }\) b/silyloxyketone 2 \(^{\prime }\) b or 1,2-ketomonoxime 1 \(^{\prime }\) c, an aldehyde 3 \(^{\prime }\), an amine, and ammonium acetate (as ammonia source) (Fig. 1a) carried out under (i) microwave irradiation conditions in the presence of silica gel/zeolite HY or silica \(\hbox {gel-NaHSO}_{4}\), and (ii) traditional heating under reflux in suitable solvents or under solvent-free condition at \(140~^{\circ }\hbox {C}\) in the presence of catalysts. Alternative synthetic approaches include the reaction of an \(\alpha \)-bromoketone 5 \(^{\prime }\) with substituted amidines 6 \(^{\prime }\) to afford 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles (Fig. 1b) or the cyclocondensation of \(N\)-alkyl-\(\upalpha \) acetamidoketone/alcohol 7 \(^{\prime }\) with ammonium acetate in acetic acid or with ammonium trifluoroacetate (as solvent) under reflux conditions to generate 1,2,4,5-tetrasubstituted imidazoles (Fig. 1c). Recently, the synthesis of 1,2,4,5-tetrasubstituted imidazoles was achieved using alkenes 8 \(^{\prime }\) via a 2-step ketoiodination/cyclisation strategy (Fig. 1d) [18].

Fig. 1
figure 1

Synthesis strategies for the construction of 1,2,4,5-tetrasubstituted imidazoles

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These methods have their own merits and drawbacks. Some of them use hazardous, toxic, and expensive reagents, giving side reactions, requiring complex work-up and purification procedures, needing strong acidic conditions, low yields, using of moisture-sensitive reagents/catalysts, requiring to synthesize starting materials, the use of auxiliary reagents, and expensive apparatus [11, 12, 18]. Therefore, to avoid these limitations, we report herein the development of \(\hbox {Sb}_{2}\hbox {O}_{3}\) catalytic systems for the convenient and efficient synthesis of 1,2,4,5-tetrasubstituted imidazoles using a 4-MCR strategy. In continuation of our interest in the synthesis of useful heterocyclic compounds possessing an imidazole core and organosilicon moieties, we have synthesized a series of new, highly substituted imidazoles containing organosilylvinyl substituent and bulky organosilicon groups using \((\hbox {RSiMe}_{2})_{3}\hbox {CLi}\) (R=H, Me, Ph).

Results and discussion

We began investigating the influence of different reaction media, amounts of catalyst, and reaction temperatures using the following as a model reaction: 4-methylbenzaldehyde (1 mmol), benzil (1 mmol), aniline (1 mmol) and ammonium acetate (1.1mmol) in the presence of a number of catalysts (Table 1). We found that the reaction performed best using \(\hbox {Sb}_{2}\hbox {O}_{3}\) under solvent-free conditions. In addition, no conversion to product was observed in the absence of catalyst, even after 8.0 h under solvent-free conditions. Compared with the reaction carried out using other catalysts, the best results were obtained when using 10 mol% \(\hbox {Sb}_{2}\hbox {O}_{3}\) at \(110~^{\circ }\hbox {C}\) for 2 h (Table 1, entry 13).

Table 1 Optimization of reaction conditions
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The scope of the reaction using \(\hbox {Sb}_{2}\hbox {O}_{3}\) (10 mol%) at \(110~^{\circ }\hbox {C}\) under solvent-free conditions was explored using a variety of aromatic aldehydes and aniline derivatives, benzil and ammonium acetate (as ammonia source) between 1-3 h. We successfully obtained 1,2,4,5-tetrasubstituted imidazoles possessing benzylic methyl group(s) in good yields.

A plausible mechanism for the catalytic participation of \(\hbox {Sb}_{2}\hbox {O}_{3}\) in the synthesis of tetrasubstituted imidazoles is postulated in Scheme 1. Herein, \(\hbox {Sb}_{2}\hbox {O}_{3}\) coordinates with and activates the carbonyl group of an aldehyde to facilitate the formation of diamine intermediate A. \(\hbox {Sb}_{2}\hbox {O}_{3}\) also activates the diketone to facilitate the condensation with intermediate A to give imidazol-5-ol intermediate C which, upon elimination of water, transformed into the desired 1,2,4,5-tetrasubstituted imidazoles.

Scheme 1
scheme 1

Plausible mechanism for the formation of 1,2,4,5-tetrasubstituted imidazoles in the presence of \(\hbox {Sb}_{2}\hbox {O}_{3}\)

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In our efforts to exemplify the usefulness of the compounds generated during this study, we used compounds 1a–1h to prepare highly substituted imidazoles bearing bulky organosilicon groups and vinylbis(silanes). We recently reported the preparation and reactions of related compounds containing organosilicon moieties [4, 5, 7, 9]. We proceeded with the bromination of the benzylic methyl group(s) in compounds 1a–1h. Initial efforts to brominate the benzylic methyl group in imidazole derivatives 1b, and 1h and 1g did not yield expected products. Even after 4 days of reaction time only low yields were obtained. Bromination of imidazole derivatives 1a, and 1c–1f was achieved using NBS in \(\hbox {CCl}_{4}\) in the presence of a catalytic amount of \(\upalpha ,\!\upalpha ^\prime \)-azobisisobutyronitrile (AIBN) at 50–52\(~^{\circ }\hbox {C}\). While bromo derivatives 2a, and 2c–2f were obtained in 48 h in good yields, 2g was obtained from 1g needing 2 eq. of NBS. The crude products were used directly for the synthesis of multisubstituted imidazoles containing bulky organosilicon groups 3, 4, and 5 via nucleophilic attack with various tris(organosilyl)methylmetals, IV–VI, in short reaction times with excellent yields. Starting materials I–III and IV–VI were synthesized using published methodologies [4–7, 19–22] (see Scheme 2).

Scheme 2
scheme 2

Preparation of tris(organosilyl)methylmetals reagents

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The rate of nucleophilic attack of IV–VI on the bromo-methyl derivatives 2a–2i decreased by increasing the steric hindrance of the R groups [4]. For the synthesis of other organosilicon-containing imidazole derivatives, V, VI were treated with formylated imidazole 6a to afford imidazole containing 2,2-bis(organosilyl)ethenyl groups. For this purpose, hydrolysis of 2a was accomplished in the presence of \(\hbox {DMSO-H}_{2}\hbox {O}\). Subsequent oxidation of the resulting mixture with IBX furnished the corresponding aldehyde 6a in excellent yield (Scheme 3). 2-(4-(2,2-bis(trimethylsilyl)vinyl)phenyl)-1,4,5-triphenyl-1\(H\)-imidazole 7a was synthesized by the reaction of tris(trimethylsilyl)methyllithium with carbonyl moiety using a Peterson olefination approach where intermediate M undergoes reactions breaking and creating new bonds and the elimination of \(\hbox {RMe}_{2}\hbox {SiOLi}\) giving 6a [4, 22–24]. In contrast, for phenyl-containing compound 8a only traces were detected (Scheme 3; Table 2).

Scheme 3
scheme 3

Synthesis of organosilicon-containing imidazoles

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Table 2 Synthesis of highly substituted imidazoles
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Table 3 Preparation of imidazoles containing bulky organosilicon groups
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Conclusion

In summary, we have established an optimized procedure for the exclusive synthesis of highly substituted imidazoles possessing benzylic methyl group(s) 1a–1h via one-pot 4-component coupling cyclization reaction catalyzed by \(\hbox {Sb}_{2}\hbox {O}_{3 }\) under solvent-free condition at \(110\,^{\circ }\hbox {C}\) in excellent yields. The formyl derivative 6a and bromo-imidazole derivatives 2a–2i were found to be excellent substrates for the synthesis of organosilicon-containing imidazoles. Highly substituted imidazoles bearing bulky organosilicon groups 3, 4, and 5 (Table 3) were obtained in excellent yields. It is worth noting that compounds 3a, 3b, 3g, and 3i are potential cores for dendrimers, which we will investigate and report about in future communications.

Experimental

Chemicals and apparatus

Chemicals were either prepared in our laboratory or purchased from Merck, Fluka and Aldrich. Commercial products were used without further purification. \(^{1}\hbox {H NMR}\) and \(^{13}\hbox {C NMR}\) spectra were recorded on a Bruker FT-400 MHz spectrometer at room temperature and using \(\hbox {CDCl}_{3}\) as internal standard and solvent. Abbreviations used for NMR signals are: s = singlet, d = doublet, t = triplet, and m = multiplet. FTIR spectra were recorded on a Bruker Tensor 270 spectrometer. Elemental analyses were carried out on an Elementar Vario EL III instrument. Melting points were recorded on a Büchi B-545 apparatus in open capillary tubes and are uncorrected.

Preparation of o-iodoxybenzoic acid (IBX)

Synthesized by oxidation of 2-iodobenzoic acid using \(\hbox {KBrO}_{3}\) and the residue IBA was recovered to IBX according to the literature [25, 26].

Preparation of tris(dimethylsilyl)methyllithium IV

A 50 mL round-bottom flask equipped with a stirrer, septum, and gas-inlet needle was charged with diisopropylamine (0.53 g, 5.3  mmol) and 15 mL of THF. The flask was placed in a water–ice bath, and then n-BuLi (3.8 mL, 1.5 M solution in hexane) was added drop-wise under magnetic stirring to form a clear yellow solution. This solution was stirred for an additional 30 min. A lithium diisopropylamide (LDA) solution was transferred into a dropping funnel, and the content was added drop-wise to a 50 mL round-bottom flask containing tris(dimethylsilyl)methane (1.0 g, 5.3 mmol) in 10  mL of THF under argon atmosphere at room temperature. The orange–red solution was stirred at ambient temperature for 10 h.

Preparation of tris(trimethylsilyl)methyllithium V

The reagent was prepared as described by Gröbel and co-workers [20].

Preparation of tris(dimethylphenylsilyl)methyllithium VI

The method for the preparation of tris(trimethylsilyl)methyllithium was used.

General procedure for preparation of 1,2,4,5-tetrasubstituted imidazoles (1a–1h)

10 mol% \(\hbox {Sb}_{2}\hbox {O}_{3}\) was added to the mixture of benzil (1 mmol), aldehyde (1 mmol), amine (1 mmol), and ammonium acetate (1.1 mmol). Then the reaction mixture was stirred on a preheated oil bath at \(110~^{\circ }\hbox {C}\). After completion of the reaction (monitored by TLC, within 1–3 h), the crude residue was allowed to cool to room temperature. The mixture was extracted with \(\hbox {CH}_{2}\hbox {Cl}_{2} (3\times 20\,\hbox {mL})\). The combined organic layers were dried over anhydrous \(\hbox {Na}_{2}\hbox {SO}_{4}\), filtered, and the solvent evaporated to give the desired crude product. This product was washed with n-hexane and purified by recrystallization from \(\hbox {CH}_{2}\hbox {Cl}_{2}\). The spectral data of selected products (1d–1f, 1h) are given below.

1-(3-Chlorophenyl)-4,5-diphenyl-2-\(p\)-tolyl-1\(H\)-imidazole 1d

White powder (89 %), M.P. = 198–200\(~^{\circ }\hbox {C},\,\nu _\mathrm{{max}}\) (KBr) 3056, 2963, 2909, 1490, 1479, 1265, 823, 739, 703 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\,\hbox {NMR} (\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 2.33 (s, 3H, CH3), 6.93–6.95 (m, 1H, ArH), 7.05 (t, \(J\,=\,1.86 \hbox {Hz},\) 1H, ArH), 7.08 (d, 2H, \(J\,=\,8.04\,\hbox {Hz},\) ArH), 7.12–7.27 (m, 10H, ArH), 7.32 (d, 2H, \(J\) = 8.15 Hz, ArH),7.58–7.60 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 20.27, 125.64, 125.77, 126.24, 126.33, 127.14, 127.15, 127.47, 127.58, 127.78, 127.95, 128.92, 129.31, 130.05, 133.21, 133.48, 137.33, 137.45, 146.00. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{21}\hbox {ClN}_{2}\): C, 79.89; H, 5.03; N, 6.66 %. Found: C, 79.78; H, 5.12; N, 6.74 %.

1-(4-Fluorophenyl)-4,5-diphenyl-2-\(p\)-tolyl-1\(H\)-imidazole 1e

White powder (85 %), M.P. = 188–190\(~^{\circ }\hbox {C},\,\nu _{\mathrm{max}}\) (KBr) 3058, 2962, 2908, 1602, 1508, 1444, 1418, 1312, 1225, 960, 775, 730 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 2.36 (s, 3H, CH3), 6.96–7.00 (m, 2H, ArH), 7.03–7.07 (m, 2H, ArH), 7.11 (d, 2H, \(J\,=\,8.0\,\hbox {Hz},\) ArH), 7.14–7.17 (m, 2H, ArH), 7.21–7.32 (m, 6H, ArH). 7.35 (d, 2H, \(J\,=\,8.0\,\hbox {Hz},\) ArH), 7.63 (d, 2H, \(J\,=\,7.2\,\hbox {Hz},\) ArH), \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 20.24, 114.95, 115.17, 125.58, 126.32, 126.41, 127.01, 127.12, 127.41, 127.79, 127.88, 128.99, 129.08, 129.50, 129.58, 130.07, 132.19, 133.30, 137.16, 137.31, 146.12, 159.59, 162.06. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{21}\hbox {FN}_{2}\): C, 83.14; H, 5.23; N, 6.93 %. Found: C, 83.09; H, 5.14; N, 6.81 %.

1-(4-Bromophenyl)-4,5-diphenyl-2-\(p\)-tolyl-1\(H\)-imidazole 1f

White powder (88 %), M.P. = 190–192\(~^{\circ }\hbox {C},\, \nu _{\mathrm{max}}\) (KBr) 3445, 3057, 2961, 2908, 1570, 1510, 1478, 1312, 1267, 833, 726, 697 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 2.36 (s, 3H, CH3), 6.93 (d, \(J\,=\,8.6\,\hbox {Hz},\) 2H, ArH), 7.11–7.17 (m, 4H, ArH), 7.20–7.35 (m, 8H, ArH), 7.41 (d, 2H, \(J\) = 8.6 Hz, ArH), 7.60–7.62 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (CDCl\(_{3}\), 100 MHz): \(\delta \) (ppm) 20.27, 121.06, 121.58, 125.64, 126.37, 127.14, 127.51, 127.88, 127.96, 128.56, 128.91, 129.35, 129.44, 130.10, 131.13, 131.25, 133.27, 135.27, 137.42, 146.04. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{21}\hbox {BrN}_{2}\): C, 72.26; H, 4.55; N, 6.02 %. Found: C, 72.14; H, 4.47; N, 6.14 %.

2-(4-Chlorophenyl)-4,5-diphenyl-1-\(p\)-tolyl-1\(H\)-imidazole 1h

White powder (92 %), M.P. = 167–169\(~^{\circ }\hbox {C},\,\nu _{\mathrm{max}}\) (KBr) 3054, 2976, 1510, 1478, 1445, 1312, 1266, 832, 745, 696 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 2.36 (s, 3H, CH3), 6.95 (d, \(J\,=\,8.1\,\hbox {Hz},\) 2H, ArH), 7.10 (d, \(J\,=\,8.1\,\hbox {Hz},\) 2H, ArH), 7.16–7.18 (m, 2H, ArH), 7.21–7.30 (m, 8H, ArH), 7.41–7.43 (m, 2H, ArH), 7.61–7.63 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 20.14, 119.77, 125.61, 126.30, 126.95, 126.99, 127.13, 127.29, 127.31, 128.10, 128.82, 129.03, 129.50, 130.05, 130.17, 133.15, 133.21, 133.31, 137.41, 144.74. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{21}\hbox {ClN}_{2}\): C, 79.89; H, 5.03; N, 6.66 %. Found: C, 79.76; H, 5.14; N, 6.86 %.

General procedure for bromination of imidazole derivatives

Compounds 2a–2h were prepared by reacting compounds 1a–1h (1 mmol) with \(N\)-bromosuccinimide (NBS) (1 mmol), and compound 2i was obtained by reacting compound 1g (1  mmol) with NBS (2 mmol) in 70 mL of carbon tetrachloride under an argon atmosphere. To initiate the reaction, 10 mol% of \(\upalpha ,\upalpha \prime \)-azobisisobutyronitrile (AIBN) was added and the reaction mixture was stirred at 50–52\(~^{\circ }\hbox {C}\). The optimum reaction time for 2a, and 2c–2g was 2 days while that for 2b, 2h, and 2i was observed to be 4  days. Then the reaction mixture was cooled to \(10~^{\circ }\hbox {C}\), and the precipitated succinimide was filtered off. The solution was washed with water three times, the organic phase dried over \(\hbox {Na}_{2}\hbox {SO}_{4}\), and the solvent evaporated under vacuum. Crude products 2a and 2e were purified by column chromatography (silica gel, hexane/ethylacetate mixture (10:1, v/v)) to afford bromo-methyl imidazoles 2a and 2e.

2-(4-(Bromomethyl)phenyl)-1,4,5-triphenyl-1\(H\)-imidazole 2a

White powder (75 %), M.P. = 160–162\(~^{\circ }\hbox {C},\,\nu _{\mathrm{max}}\) (KBr) 3058, 2922, 1600, 1495, 1446, 1384, 1228, 764, 736, 697, 534 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 4.45 (s, 2H, \(\hbox {CH}_{2}\)), 7.04-7.06 (m, 2H, Ar-H), 7.11–7.13 (m, 2H, Ar-H), 7.18–7.33 (m, 11H, Ar-H), 7.41 (d, \(J\,=\,8.2\,\hbox {Hz},\) 2H, Ar-H), 7.58 (d, \(J\,=\,7.2\,\hbox {Hz},\) 2H, Ar-H). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 32.11, 125.65, 126.34, 126.40, 127.00, 127.15, 127.27, 127.32, 127.36, 127.41, 127.79, 127.83, 128.00, 128.07, 128.16, 130.05, 135.94, 136.52, 145.10. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{21}\hbox {BrN}_{2}\): C, 72.26; H, 4.55; N, 6.02 %. Found: C, 72.21; H, 4.59; N, 6.24 %.

2-(4-(Bromomethyl)phenyl)-1-(4-fluorophenyl)-4,5-diphenyl-1\(H\)-imidazole 2e

White powder (73 %), M.P. = 152–154\(~^{\circ }\hbox {C},\,\nu _{\mathrm{max}}\) (KBr) 3058, 1603, 1509, 1446, 1225, 825, 777, 733, 698, 532 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 4.49 (s, 2H), 6.99–7.09 (m, 4H, Ar-H), 7.16 (dd, \(J\,=\,1.6\,\hbox {Hz},\,J\,=\,7.8\,\hbox {Hz},\) 2H, Ar-H), 7.24–7.34 (m, 8H, Ar-H), 7.44 (d, \(J\,=\,8.3\,\hbox {Hz},\) 2H, Ar-H), 7.60–7.63 (m, 2H, Ar-H). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 31.98, 115.165, 115.39, 125.77, 126.32, 127.19, 127.48, 127.94, 128.01, 128.12, 128.99, 129.07, 129.22, 130.05, 131.95, 133.03, 136.78, 159.75, 162.23. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{20}\hbox {BrFN}_{2}\): C, 69.57; H, 4.17; N, 5.80 %. Found: C, 69.45; H, 4.09; N, 5.72 %.

Preparation of 4-(1,4,5-triphenyl-1H-imidazol-2-yl)benzaldehyde 6a

A mixture of bromo-imidazole 2a and starting material 1a was taken up in \(\hbox {DMSO/H}_{2}\hbox {O}\) (100 mL, 90:10, v/v) and stirred at \(80~^{\circ }\hbox {C}\). After completion of the reaction (monitored by TLC, within 3–6 h), the reaction mixture was quenched with excess of cold water (150 mL), extracted with ethylacetate \((2\times 20\,\hbox {mL})\), and dried \((\hbox {Na}_{2}\hbox {SO}_{4})\), the organic phase was evaporated under reduced pressure. To crude product of appropriate alcohol, was added \(o\)-iodoxybenzoic acid (IBX) (1.2 mmol) and the resulting mixture was stirred at \(80~^{\circ }\hbox {C}\) for 4 h. Then the residue was subjected to column chromatography over silica gel using (8:2, v/v) hexane/ethylacetate mixture as eluent to give unreacted starting material 1a. Further elution with (1:1, v/v) hexane/ethylacetate furnished the aldehyde 6a.

White powder (97 %), M.P. = 157–159\(~^{\circ }\hbox {C},\,\nu _{\mathrm{max}}\) (KBr) 3068, 2962, 2933, 2872, 2734, 1691, 1599, 1507, 1475, 1411, 1255, 1093, 831, 747, 648 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 7.07 (dd, \(J \)= 1.5 Hz, \(J\,=\,8.0\,\hbox {Hz},\) 2H, ArH), 7.13 (dd, \(J\,=\,1.5\,Hz,\,J\,= 8.0\,\hbox {Hz},\) 2H, ArH), 7.22–7.32 (m, 9H, ArH), 7.42 (d, \(J\,= 8.6\,\hbox {Hz},\) 2H, ArH), 7.46–7.48 (m, 2H, ArH), 7.58–7.60 (m, 2H, ArH), 9.51 (s, 1H, HC=O). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 125.77, 126.31, 126.37, 126.95, 127.03, 127.11, 127.20, 127.36, 127.38, 127.56, 128.13, 128.26, 129.31, 130.06, 131.36, 135.94, 141.66, 190.04. Anal.Calcd for \(\hbox {C}_{28}\hbox {H}_{20}\hbox {N}_{2}\hbox {O}\): C, 83.98; H, 5.03; N, 7.00 %. Found: C, 83.85; H, 4.99; N, 7.12 %.

General procedure for the synthesis of 2-(4-(2,2-bis(triorganosilyl)vinyl)phenyl)-1,4,5-triphenyl-1H-imidazoles

To a stirred solution of VI or Vand/or VI (5.3 mmol) in THF at room temperature was added aldehyde 6a (5.0 mmol) in 10 mL THF, and then stirred for 3–5  min at room temperature. The reaction mixture was poured onto an aqueous ammonium chloride solution (50 mL) and extracted with \(\hbox {CH}_{2}\hbox {Cl}_{2}\,(2\times 50\,\hbox {mL})\). The organic phase was washed with water (100 mL), dried \((\hbox {Na}_{2}\hbox {SO}_{4})\), and the solvent was removed to yield desired product as a white solid.

2-(4-(2,2-Bis(trimethylsilyl)vinyl)phenyl)-1,4,5-triphenyl-1\(H\)-imidazole 7a

White powder (98 %), M.P. = 120–122\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3386, 3031, 2959, 1648, 1605, 1501, 1410, 1244, 836 (Si–CH3), 764, 686 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) \(-0.08\) (s, 9H, \(\hbox {SiMe}_{3})\), 0.17 (s, 9H, \(\hbox {SiMe}_{3})\), 7.01 (dd, \(J\,= 1.6\,Hz,\,J\,=\,8.0\,\hbox {Hz},\) 2H, ArH), 7.05 (d, 2H, \(J\,=\,8.1\,\hbox {Hz},\) ArH), 7.13 (dd, \(J\,=\,1.6\,\hbox {Hz},\,J\,=\,8.00\,\hbox {Hz},\) 2H, ArH), 7.19–7.27 (m, 9H, ArH), 7.34 (d, 2H, \(J\,=\,8.1\,\hbox {Hz},\) ArH), 7.60 (dd, \(J\,=\,1.2\,\hbox {Hz},\,J\,=\,8.4\,\hbox {Hz},\) 2H, ArH), 7.69 (s, 1H, HC=). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) -0.53 \((\hbox {SiMe}_{3})\), 1.01 \((\hbox {SiMe}_{3})\), 125.57, 126.28, 126.43, 126.55, 126.92, 127.14, 127.31, 127.40, 127.42, 127.53, 128.02, 129.58, 129.76, 130.08, 133.40, 136.04, 141.68, 145.84, 146.26, 153.15. Anal.Calcd for \(\hbox {C}_{35}\hbox {H}_{38}\hbox {N}_{2}\hbox {Si}_{2}\): C, 77.44; H, 7.06; N, 5.16 %. Found: C, 77.48; H, 7.16; N, 5.10 %.

Tris(dimethylphenylsilyl)methyllithium did not react with 6a under reflux conditions in THF for 3 h.

Preparation of imidazoles containing bulky organosilicon groups \({{(RSi{Me_{2}})}_{3}}\)C- (R= H, Me, Ph)

To a stirred solution of VI orVand/or VI (5 mmol) in THF was added a mixture of 2a–2g (5 mmol) in 10 mL THF and or (2.5 mmol) of 2i in THF at room temperature. The mixture was stirred for another 10 min at room temperature. The mixture was poured onto an ammonium chloride aqueous (50 mL) and extracted with \(\hbox {CH}_{2}\hbox {Cl}_{2}\,(2\times 20\,\hbox {mL})\). The organic phase was washed with water (100 mL), dried \((\hbox {Na}_{2}\hbox {SO}_{4})\), and the solvent removed in vacuum to yield a yellow solid.

Selected spectral data of the products

2-(4-(2,2,2-Tris(dimethylsilyl)ethyl)phenyl)-1,4,5-triphenyl-1H-imidazole (3a)

White powder (93 %), M.P. = 140–142\(~^{\circ }\hbox {C}\), \(\nu _{\mathrm{max}}\) (KBr) 3419, 3060, 2956, 2902, 2112 (Si–H), 1599, 1496, 1445, 1419, 1390, 1254, 960, 836 \((\hbox {Si--CH}_{3})\), 765, 695 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.1–0.11 (d, 18H, \(\hbox {SiMe}_{2})\), 3.00 (s, 2H, \(\hbox {CH}_{2})\), 4.03–4.04 (m, 3H, Si–H), 7.00 (d, \(J\,=\,7.3\,\hbox {Hz},\) 2H, ArH), 7.11–7.31 (m, 15H, ArH)), 7.59 (d, 2H, \(J\,=\,7.3\,\hbox {Hz},\) ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) -4.09 \((\hbox {SiMe}_{2})\), 3.41 \((\hbox {C}(\hbox {SiMe}_{2})_{3})\), 34.71 \((\hbox {CH}_{2})\), 125.55, 126.47, 126.87, 127.08, 127.11, 127.28, 127.38, 127.50, 127.97, 129.16, 129.59, 129.61, 130.08, 133.37, 136.00, 137.17, 139.78, 145.96. Anal.Calcd for \(\hbox {C}_{35}\hbox {H}_{42}\hbox {N}_{2}\hbox {Si}_{3}\): C, 73.11; H, 7.36; N, 4.87 %. Found: C, 73.23; H, 7.32; N, 4.69 %.

2-(4-(2,2,2-Tris(dimethylsilyl)ethyl)phenyl)-1-(3-chlorophenyl)-4,5-diphenyl-1H-imidazole (3d)

White powder (92 %), M.P. = 132–134\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3062, 2958, 2925, 2113 (Si–H), 1590, 1479, 1445, 1420,1256, 961, 835 \((\hbox {Si-CH}_{3})\), 693 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.10–0.11 (d, 18H, \(\hbox {SiMe}_{2}\)), 3.01 (s, 2H, \(\hbox {CH}_{2}\)), 4.01–4.05 (m, 3H, Si–H), 6.89–6.92 (m, 1H, ArH), 7.02 (t, \(J\,=\,1.9\,\hbox {Hz},\) 1H, ArH), 7.11–7.31 (m, 14H, ArH), 7.57–7.60 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100  MHz): \(\delta \) (ppm) \(-4.09\) \((\hbox {SiMe}_{2})\), 3.40 \((\hbox {C}(\hbox {SiMe}_{2})_{3})\), 34.76 \((\hbox {CH}_{2})\), 125.67, 125.73, 126.39, 127.04, 127.15, 127.43, 127.47, 127.53, 128.87, 129.25, 129.34, 129.47, 130.05, 133.18, 133.52, 137.20, 140.09, 145.91. Anal.Calcd for \(\hbox {C}_{35}\hbox {H}_{41}\hbox {ClN}_{2}\hbox {Si}_{3}\): C, 68.98; H, 6.78; N, 4.60 %. Found: C, 68.81; H, 6.69; N, 4.61 %.

2-(4-(2,2,2-Tris(dimethylsilyl)ethyl)phenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (3g)

White powder (92 %), M.P. = 138–140\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3059 (Ar–H), 2958 (C-H), 2904, 2114 (Si-H), 1601, 1512, 1450 (Ar), 1419, 1256, 835 \((\hbox {Si-CH}_{3})\), 802, 695 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.13–0.14 (d, 18H, \(\hbox {SiMe}_{2})\), 2.34 (s, 3H, \(\hbox {CH}_{3})\), 3.03 (s, 2H, \(\hbox {CH}_{2}\)), 4.04–4.08 (m, 3H, Si-H), 6.91 (d, \(J\,=\,8.1\,\hbox {Hz},\) 2H, ArH), 7.05 (d, \(J\,=\,8.1\,\hbox {Hz},\) 2H, ArH), 7.15–7.42 (m, 12H, ArH)), 7.62 (d, 2H, \(J\,=\,7.3\,\hbox {Hz},\) ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) \(-4.05\) \((\hbox {SiMe}_{2})\), 3.40 \((\hbox {C}(\hbox {SiMe}_{2})_{3})\), 20.14 \((\hbox {CH}_{3})\), 34.73 \((\hbox {CH}_{2})\), 125.46, 126.31, 126.44, 126.80, 127.10, 127.27, 127.48, 127.60, 128.60, 129.12, 129.69, 129.80, 130.12, 133.46, 133.57, 136.95, 139.69. Anal.Calcd for \(\hbox {C}_{36}\hbox {H}_{44}\hbox {N}_{2}\hbox {Si}_{3}\): C, 73.41; H, 7.53; N, 4.76 %. Found: C, 73.21; H, 7.48; N, 4.66 %.

1,2-Bis(4-(2,2,2-tris(dimethylsilyl)ethyl)phenyl)-4,5-diphenyl-1H-imidazole (3i)

White powder (91 %), M.P. = 143–145\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3414, 3034, 2956, 2924, 2112 (Si–H), 1613, 1512, 1454, 1417, 1255, 960, 834 \((\hbox {Si--CH}_{3})\), 694 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.09–0.10 (d, 18H, \(\hbox {SiMe}_{2}\)), 0.10–0.11 (d, 18H, \(\hbox {SiMe}_{2}\)), 2.98 (s, 4H, \(2\times \hbox {CH}_{2}\)), 3.99–4.05 (m, 6H, Si–H), 6.89 (d, \(J\,=\,8.2\,\hbox {Hz},\) 2H, ArH), 7.09–7.24 (m, 10H, ArH), 7.27–7.38 (m, 4H, ArH)), 7.57–7.59 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) \(-4.09\) \((\hbox {SiMe}_{2})\), \(-4.06\) \((\hbox {SiMe}_{2})\), 3.38 \((\hbox {C}(\hbox {SiMe}_{2})_{3})\), 34.71 \((\hbox {CH}_{2})\), 125.48, 126.31, 126.42, 126.64, 126.81, 127.10, 127.35, 127.39, 127.49, 129.20, 130.15, 130.2. Anal.Calcd for \(\hbox {C}_{43}\hbox {H}_{64}\hbox {N}_{2}\hbox {Si}_{6}\): C, 66.43; H, 8.30; N, 3.60 %. Found: C, 66.41; H, 8.27; N, 3.52 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-1,4,5-triphenyl-1H-imidazole (4a)

White powder (90 %), M.P. = 198–200\(~^{\circ }\hbox {C}\), \(\nu _{\mathrm{max}}\) (KBr) 3062, 2953, 1600, 1498, 1450, 1392, 1256, 937, 840 (Si–CH3), 769, 695 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.10 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.15 (s, 2H, \(\hbox {CH}_{2}\)), 7.00 (d, \(J \)= 6.4 Hz, 2H, ArH), 7.14 (d, \(J\,=\,5.0\,\hbox {Hz},\) 2H, ArH), 7.18–7.27 (m, 13H, ArH)), 7.61 (d, 2H, \(J\,=\,6.8\,\hbox {Hz},\) ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.44 \((\hbox {SiMe}_{3})\), 9.95 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.51 \((\hbox {CH}_{2})\), 125.52, 126.47, 126.86, 127.00, 127.12, 127.28, 127.42, 127.71, 127.98, 129.26, 129.60, 129.64, 130.09, 133.47, 136.03, 137.24, 141.91, 145.95. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{48}\hbox {N}_{2}\hbox {Si}_{3}\): C, 73.96; H, 7.84; N, 4.54 %. Found: C, 73.91; H, 7.82; N, 4.52 %.

1-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-2,4,5-triphenyl-1H-imidazole (4b)

White powder (91 %), M.P. = 168–170\(~^{\circ }\hbox {C}\), \(\nu _{\mathrm{max}}\) (KBr) 3442, 3059, 2953, 2901, 1509, 1478, 1445, 1390, 1256, 938, 841 \((\hbox {Si--CH}_{3})\), 768, 695 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.07 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.11 (s, 2H, \(\hbox {CH}_{2})\), 6.89 (d, \(J\,=\,8.0\,\hbox {Hz},\) 2H, ArH), 7.12 (d, \(J\,=\,6.4\,\hbox {Hz},\) 2H, ArH), 7.19–7.26 (m, 11H, ArH)), 7.45 (d, 2H, \(J\,=\,6.7\,\hbox {Hz},\) ArH)), 7.58 (d, 2H, \(J\,=\,7.4\,\hbox {Hz},\) ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.49 \((\hbox {SiMe}_{3})\), 10.07 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.45 \((\hbox {CH}_{2})\), 125.53, 126.37, 126.62, 126.84, 126.96, 127.11, 127.17, 127.42, 127.87, 128.06, 129.50, 130.11, 130.20, 130.37, 133.33, 134.11, 137.09, 142.00. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{48}\hbox {N}_{2}\hbox {Si}_{3}\): C, 73.96; H, 7.84; N, 4.54 %. Found: C, 73.89; H, 7.87; N, 4.60 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazole (4c)

White powder (92 %), M.P. = 181–183\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3426, 3060, 2956, 2900, 1603, 1493, 1448, 1258, 940, 840 \((\hbox {Si--CH}_{3})\), 727, 697 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.01 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.16 (s, 2H, \(\hbox {CH}_{2}\)), 6.92 (d, 2H, \(J\,=\,7.9\,\hbox {Hz},\) ArH), 7.12–7.28 (m, 14H, ArH)), 7.58 (d, \(J\,=\,7.56\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.46 \((\hbox {SiMe}_{3})\), 10.12 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.56 \((\hbox {CH}_{2})\), 125.66, 126.44, 127.15, 127.50, 127.77, 128.25, 128.63, 129.44, 130.09, 132.94, 133.27, 134.62, 137.47, 142.24, 146.00. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{47}\hbox {ClN}_{2}\hbox {Si}_{3}\): C, 70.05; H, 7.27; N, 4.30 %. Found: C, 70.62; H, 7.31; N, 4.41 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-1-(3-chlorophenyl)-4,5-diphenyl-1H-imidazole (4d)

White powder (90 %), M.P. = 116–118\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3446, 3064, 2953, 1417, 1412, 1254, 935, 835, 688 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.10 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.17 (s, 2H, \(\hbox {CH}_{2}\)), 6.90 (d, \(J\,=\,7.7\,\hbox {Hz},\) 1H, ArH), 7.03 (s, 1H, ArH), 7.13–7.31 (m, 14H, ArH), 7.59 (d, 2H, \(J\,=\,7.3\,\hbox {Hz},\) ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.43 \((\hbox {SiMe}_{3})\), 9.95 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.54 \((\hbox {CH}_{2})\), 124.98, 125.66, 125.79, 126.40, 127.00, 127.14, 127.39, 127.46, 127.52, 127.66, 128.87, 129.26, 129.43, 130.05, 133.20, 133.53, 137.21, 142.25, 145.86. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{47}\hbox {ClN}_{2}\hbox {Si}_{3}\): C, 70.05; H, 7.27; N, 4.30 %. Found: C, 70.09; H, 7.27; N, 4.31 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-1-(4-fluorophenyl)-4,5-diphenyl-1H-imidazole (4e)

White powder (91 %), M.P. = 188–190\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3443, 3064, 2925, 1560, 1506, 1448, 1251, 937, 833 \((\hbox {Si--CH}_{3})\), 778, 674 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.086 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.15 (s, 2H, \(\hbox {CH}_{2}\)), 6.89–6.98 (m, 4H, ArH), 7.11 (dd, \(J\,=\,1.6\,\hbox {Hz}, \,J \,=\,7.6\,\hbox {Hz},\) 2H, ArH), 7.19–7.32 (m, 10H, ArH)), 7.57–7.59 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.42 \((\hbox {SiMe}_{3})\), 10.00 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.51 \((\hbox {CH}_{2})\), 114.90, 115.13, 125.61, 126.41, 127.04, 127.14, 127.18, 127.42, 127.71, 129.00, 129.10, 129.37, 129.44, 129.56, 130.06, 132.10, 133.28, 137.29, 142.14, 146.03, 159.54, 162.01. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{47}\hbox {FN}_{2}\hbox {Si}_{3}\): C, 71.87; H, 7.46; N, 4.41 %. Found: C, 71.80; H, 7.47; N, 4.52 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-1-(4-bromophenyl)-4,5-diphenyl-1H-imidazole (4f)

White powder (92 %), M.P. = 179–181\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3060, 2954, 1605, 1489, 1446, 1390, 1257, 936, 839 (Si–CH3), 777, 737, 698 cm-1. \(^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.08 (s, 27H, \(\hbox {SiMe}_{3}\)), 3.15 (s, 2H, \(\hbox {CH}_{2}\)), 6.83 (d, \(J\,=\,8.6\,\hbox {Hz},\) 2H, ArH), 7.10–7.12 (dd, \(J\,=\,1.7\,\hbox {Hz},\,J\,=\,7.7\hbox {Hz},\) 2H, ArH), 7.19–7.27 (m, 10H, ArH)), 7.33 (d, 2H, \(J\,=\,8.6\,\hbox {Hz},\) ArH), 7.55–7.58 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.45 \((\hbox {SiMe}_{3})\), 10.12 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 34.53 \((\hbox {CH}_{2})\), 120.95, 125.66, 126.44, 127.13, 127.15, 127.28, 127.44, 127.52, 127.79, 128.93, 129.30, 129.35, 129.44, 130.08, 131.23, 133.24, 135.10, 137.49, 145.26. Anal.Calcd for \(\hbox {C}_{38}\hbox {H}_{47}\hbox {BrN}_{2}\hbox {Si}_{3}\): C, 65.58; H, 6.81; N, 4.03 %. Found: C, 65.48; H, 6.79; N, 4.00 %.

2-(4-(2,2,2-Tris(trimethylsilyl)ethyl)phenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (4g)

White powder (91 %), M.P. = 165–167\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3444, 3056, 2953, 1512, 1448, 1257, 939, 838 \((\hbox {Si--CH}_{3})\), 776, 696 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.07 (s, 27H, \(\hbox {SiMe}_{3}\)), 2.30 (s, 3H, \(\hbox {CH}_{3})\), 3.13 (s, 2H, \(\hbox {CH}_{2})\), 6.85 (d, 2H, \(J\,=\,8.0\,\hbox {Hz},\) ArH), 7.00 (d, \(J\,=\,8.0\,\hbox {Hz},\) 2H, ArH).7.11–7.26 (m, 12H, ArH)), 7.57 (d, \(J\,=\,7.3\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.44 \((\hbox {SiMe}_{3})\), 10.05 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 20.09 \((\hbox {CH}_{3})\), 34.53 \((\hbox {CH}_{2})\), 125.47, 126.00, 126.31, 126.48, 126.71, 126.80, 127.10, 127.14, 127.26, 127.49, 127.73, 128.61, 128.76, 129.21, 130.12, 133.56, 136.91, 141.80. Anal.Calcd for \(\hbox {C}_{39}\hbox {H}_{50}\hbox {N}_{2}\hbox {Si}_{3}\): C, 74.22; H, 7.99; N, 4.36 %. Found: C, 74.19; H, 7.90; N, 4.41 %.

1,2-Bis(4-(2,2,2-tris(trimethylsilyl)ethyl)phenyl)-4,5-diphenyl-1H-imidazole (4i)

White powder (89 %), M.P. = 170–172\(~^{\circ }\hbox {C}\), \(\nu _{\mathrm{max}}\) (KBr) 3417, 3060, 2955, 1510, 1451, 1257, 938, 838 (Si–CH3), 677 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.08 (s, 54H, \(2\times \hbox {SiMe}_{3}\)), 3.11 (s, 2H, \(\hbox {CH}_{2}\)), 3.13 (s, 2H, \(\hbox {CH}_{2})\), 6.84–6.86(m, 2H, ArH), 7.09–7.36 (m, 14H, ArH)), 7.58 (d, \(J\,=\,7.2\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.43 \((\hbox {SiMe}_{3})\), 2.50 \((\hbox {SiMe}_{3})\), 34.45\((\hbox {CH}_{2})\), 34.52 \((\hbox {CH}_{2})\), 125.48, 126.45, 126.74, 127.06, 127.10, 127.39, 127.61, 127.66, 127.94, 128.65, 129.28, 129.59, 130.00, 130.17, 130.32, 134.26, 141.87, 141.97. Anal.Calcd for \(\hbox {C}_{49}\hbox {H}_{76}\hbox {N}_{2}\hbox {Si}_{6}\): C, 68.30; H, 8.89; N, 3.25 %. Found: C, 68.28; H, 8.79; N, 3.34 %.

2-(4-(2,2,2-Tris(dimethyl(phenyl)silyl)ethyl)phenyl)-1,4,5-triphenyl-1H-imidazole (5a)

White powder (88 %), M.P. =220–222\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 34119, 3065, 2959, 2922, 1598, 1494, 1450, 1253, 931, 836 \((\hbox {Si--CH}_{3})\), 764, 700 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.19 (s, 18H, \(\hbox {SiMe}_{3})\), 3.56 (s, 2H, \(\hbox {CH}_{2})\), 7.05 (d, 2H, \(J\,=\,7.2\,\hbox {Hz},\) ArH), 7.13 (d, \(J\,=\,6.2\,\hbox {Hz},\) 2H, ArH), 7.21–7.26 (m, 14H, ArH), 7.28–7.33 (m, 8H, ArH), 7.36–7.38 (m, 6H, ArH), 7.61 (d, \(J\,=\,7.2\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 1.45 \((\hbox {SiMe}_{3})\), 12.68 (C\((\hbox {SiMe}_{3})_{3})\), 35.32 \((\hbox {CH}_{2})\), 125.54, 126.24, 126.38, 126.43, 126.88, 127.12, 127.28, 127.41, 127.45, 127.67, 128.04, 129.62, 129.74, 130.08, 130.17, 133.47, 134.29, 136.13, 137.32, 139.63, 140.90, 145.74. Anal.Calcd for \(\hbox {C}_{53}\hbox {H}_{54}\hbox {N}_{2}\hbox {Si}_{3}\): C, 79.25; H, 6.78; N, 3.49 %. Found: C, 79.15; H, 6.70; N, 3.51 %.

2-(4-(2,2,2-Tris(dimethyl(phenyl)silyl)ethyl)phenyl)-1-(4-chlorophenyl)-4,5-diphenyl-1H-imidazole (5c)

White powder (87 %), M.P. = 198–200\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3445, 3063, 2960, 2909, 1603, 1490, 1423, 1312, 1252, 932, 836 \((\hbox {Si--CH}_{3})\), 736, 701 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.22 (s, 18H, \(\hbox {SiMe}_{3}\)), 3.59 (s, 2H, \(\hbox {CH}_{2})\), 6.98 (d, 2H, \(J\,=\,8.3\,\hbox {Hz},\) ArH), 7.13–7.40 (m, 29H, ArH), 7.61 (d, \(J\,=\,7.4\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 1.47 \((\hbox {SiMe}_{3})\), 12.76 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 35.37 \((\hbox {CH}_{2})\), 125.70, 126.19, 126.43, 126.81, 127.18, 127.39, 127.51, 127.73, 128.10, 128.31, 128.59, 129.35, 129.54, 129.86, 130.08, 130.32, 133.05, 133.24, 134.30, 134.69, 137.58, 139.62, 141.26, 145.75. Anal.Calcd for \(\hbox {C}_{53}\hbox {H}_{53}\hbox {ClN}_{2}\hbox {Si}_{3}\): C, 75.99; H, 6.38; N, 3.34 %. Found: C, 75.96; H, 6.40; N, 3.38 %.

2-(4-(2,2,2-Tris(dimethyl(phenyl)silyl)ethyl)phenyl)-1-(3-chlorophenyl)-4,5-diphenyl-1H-imidazole (5d)

White powder (89 %), M.P. = 196–198\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3066, 3046, 2990, 2959, 2908, 1589, 1532, 1479, 1425, 1253, 958, 836 \((\hbox {Si--CH}_{3})\), 734, 698 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.3 (s, 18H, \(\hbox {SiMe}_{3})\), 3.68 (s, 2H, \(\hbox {CH}_{2})\), 7.04–7.05(m, 1H, ArH), 7.16 (t, \(J\,=\,1.9\,\hbox {Hz},\) 1H, ArH), 7.20–7.24 (m, 3H, ArH), 7.29–7.42 (m, 20H, ArH), 7.46–7.48 (m, 6H, ArH), 7.69–7.71 (m, 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 1.44 \((\hbox {SiMe}_{3})\), 12.58 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 35.33 \((\hbox {CH}_{2})\), 125.69, 125.75, 126.15, 126.39, 127.16, 127.26, 127.40, 127.48, 127.70, 128.96 129.18, 129.58, 130.02, 130.30, 133.17, 133.57, 134.27, 137.26, 137.50, 139.58, 141.24, 145.65. Anal.Calcd for \(\hbox {C}_{53}\hbox {H}_{53}\hbox {ClN}_{2}\hbox {Si}_{3}\): C, 75.99; H, 6.38; N, 3.34 %. Found: C, 75.89; H, 6.30; N, 3.42 %.

2-(4-(2,2,2-Tris(dimethyl(phenyl)silyl)ethyl)phenyl)-1-(4-fluorophenyl)-4,5-diphenyl-1H-imidazole (5e)

White powder (85 %), M.P. = 189–191\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3417, 3064, 2957, 2917, 1605, 1563, 1507, 1424, 1312, 1251, 930, 837 \((\hbox {Si--CH}_{3})\), 735, 701 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.25 (s, 18H, \(\hbox {SiMe}_{3})\), 3.63 (s, 2H, \(\hbox {CH}_{2})\), 7.28–7.44 (m, 31H, ArH), 7.66 (d, \(J\,=\,7.1\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 1.44 \((\hbox {SiMe}_{3})\), 12.70 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 35.32 \((\hbox {CH}_{2})\), 115.02, 115.24, 125.67, 126.41, 127.08, 127.18, 127.45, 127.58, 127.73, 127.76, 127.82, 127.95, 128.99, 129.08, 130.07, 130.24, 130.29, 134.29, 137.41, 139.60, 141.15, 159.60, 162.07. Anal.Calcd for \(\hbox {C}_{53}\hbox {H}_{53}\hbox {FN}_{2}\hbox {Si}_{3}\): C, 77.51; H, 6.50; N, 3.41 %. Found: C, 77.49; H, 6.52; N, 3.34 %.

2-(4-(2,2,2-Tris(dimethyl(phenyl)silyl)ethyl)phenyl)-4,5-diphenyl-1-p-tolyl-1H-imidazole (5g)

White powder (87 %), M.P. = 203–205\(~^{\circ }\hbox {C} ,\,\nu _{\mathrm{max}}\) (KBr) 3419, 3065, 2959, 2922, 1598, 1494, 1450, 1254, 931, 836 \((\hbox {Si--CH}_{3})\), 764, 700 \(\hbox {cm}^{-1}.\,^{1}\hbox {H}\) NMR (\(\hbox {CDCl}_{3}\), 400 MHz): \(\delta \) (ppm) 0.24 (s, 18H, \(\hbox {SiMe}_{3}\)), 2.32 (s, 3H, \(\hbox {CH}_{3}\)), 3.61 (s, 2H, \(\hbox {CH}_{2}\)), 6.97 (d, 2H, \(J\,=\,8.1\,\hbox {Hz},\) ArH), 7.05 (d, \(J\,=\,8.1\,\hbox {Hz},\) 2H, ArH), 7.18–7.43 (m, 27H, ArH), 7.65 (d, \(J\,=\,7.5\,\hbox {Hz},\) 2H, ArH). \(^{13}\hbox {C}\) NMR (\(\hbox {CDCl}_{3}\), 100 MHz): \(\delta \) (ppm) 2.15 \((\hbox {SiMe}_{3})\), 13.39 \((\hbox {C}(\hbox {SiMe}_{3})_{3})\), 20.83 \((\hbox {CH}_{3})\), 36.03 \((\hbox {CH}_{2})\), 126.21, 126.97, 127.10, 127.15, 127.52, 127.79, 127.83, 127.98, 128.17, 128.20, 128.38, 128.47, 128.50, 129.37, 130.42, 130.81, 130.85, 134.19, 134.93, 135.01, 137.74, 140.35, 141.51, 146.49. Anal.Calcd for \(\hbox {C}_{54}\hbox {H}_{56}\hbox {N}_{2}\hbox {Si}_{3}\): C, 79.36; H, 6.91; N, 3.43 %. Found: C, 79.25; H, 6.89; N, 3.38 %.