H. Yu et al. / Chinese Chemical Letters 23 (2012) 573–575
575
1. Experimental
A mixture of thionyl chloride (50 mL) and N-phenyl benzamide (25 mmol) was refluxed for 2 h in a 100 mL round
bottom flask protected with a calcium chloride guard tube. The reaction mixture was cooled, the condenser was set for
downward distillation and the excess thionyl chloride was removed by distillation. The residue was further purified by
distillation under reduced pressure to give the pure imidoyl chlorides 1a in nearly quantitative yield [6].
A schlenk tube was charged with the mixture of o-bromoaniline 1a (0.5 mmol), Cs2CO3 (1.5 mmol, 0.49 g), CuI
(5 mol%, 5 mg), 1,10-phenanthroline (10 mol%, 9 mg) and imidoyl chloride 2a (0.5 mmol) then stirred in NMP
(2 mL) at 100 8C for 12 h. After completion of the reaction, the mixture was cooled to room temperature, then H2O
(5 mL) was added and the mixture was extracted with EtOAc (3 ꢁ 5 mL) and dried by anhydrous Na2SO4.
Evaporation of the solvent followed by purification on silica gel (petroleum ether/dichloromethane = 2/1) provided the
corresponding product. 3a [7]: White solid, mp 109 8C (lit. [7b] 110 8C) 1H NMR (400 MHz, CDCl3): d 7.86 (d, 1H,
J = 7.8 Hz), 7.55–7.43 (m, 5H), 7.32–7.24 (m, 8H); 13C NMR (100 MHz, CDCl3): d 152.8, 143.5, 137.6, 137.4, 130.3,
1
130.0, 129.0, 128.8, 127.7, 123.6, 123.3, 120.2, 116.7, 110.9. 3b [8]: White solid, mp 93 8C, H NMR (400 MHz,
CDCl3): d 7.98 (d, 1H, J = 1.1 Hz), 7.61–7.53 (m, 2H), 7.56–7.54 (m, 1H), 7.42 (dd, 1H, J = 8.7, 1.1 Hz), 7.38–7.33
(m, 2H), 7.16 (d, 1H, J = 8.7 Hz), 2.55 (s, 3H); 13C NMR (100 MHz, CDCl3): d 153.4, 142.0, 138.5, 135.4, 130.3,
129.2, 126.8, 125.1, 124.8, 119.3, 116.2.
In conclusion, we have developed a concise method to synthesize 1,2-disubstituted benzimidazoles using CuI as
catalyst and various 1,2-disubstituted benzimidazole were obtained.
Acknowledgment
We thank NSFC for the financial support (No. 20802053).
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