Organocatalytic Synthesis of Benzimidazole Derivatives

Abstract

A synthetic route for the production of chiral derivatives of benzimidazole is presented. Different commercially available amines are evaluated as organocatalysts for the stereoselective aldol addition of N1-benzimidazolyl acetaldehyde, previously prepared by N-alkylation of benzimidazole, with cyclic ketones. When cyclohexanone was used,0 L-prolinamide proved to be the most efficient catalyst, giving (S)-2-((R)- 2-(1H-benzo[d]imidazol-1-yl)-1-hydroxyethyl)cyclohexanone in 92% yield, 90% ee and 92:8 dr (anti/syn).