Lewis Acid-Mediated Ring Contraction of 2,4-Diaryl-2,3-dihydro-1H-1,5-benzodiazepines: Access to 2-Aryl-1-styrylbenzimidazoles |
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| Authors: | Mengyao Zhang Qiuyue Wu Jiaxi Xu |
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| Institution: | State Key Laboratory of Chemical Resource Engineering, Department of Organic Chemistry, College of Chemistry, Beijing University of Chemical Technology, Beijing, 100029 P. R. China |
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| Abstract: | 2,4-Diaryl-2,3-dihydro-1H-1,5-benzodiazepines readily undergo a ring contraction to generate 2-aryl-1-styrylbenzimidazoles in the presence of some Lewis acids. Copper acetate shows high efficiency compared with other Lewis acids. The ring contraction includes Lewis acid-catalyzed intramolecular addition, ammonium-induced ring-opening of the generated four-membered azetidine ring, deprotonation, and amine-promoted nucleophilic styryl 1,2-shift and elimination. Copper acetate serves as Lewis acid, base, and oxidant. The current reaction provides an efficient method for the convenient synthesis of 2-aryl-1-styrylbenzimidazole derivatives from readily available 2,4-diaryl-2,3-dihydro-1H-1,5-benzodiazepines. |
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| Keywords: | Benzimidazoles benzodiazepines copper acetate Lewis acids ring contraction |
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