One-Pot Synthesis of Multisubstituted Benzimidazoles via Sequential Ugi and Catalytic Aza-Wittig Reaction Starting from 2-Aminobenzoyl Azides

A simple and one-pot synthesis of multisubstituted benzimidazoles by a Ugi 4CC/catalytic aza-Wittig sequence was developed. The reaction of 2-aminobenzoyl azide 2, aldehyde 3, acid 4, and isocyanide 5 produced the benzimidazoles 8 in moderate to good yields via a sequential Ugi condensation and catalytic aza-Wittig in the presence of a catalytic amount of phospholene oxide.