Multicomponent Reaction of Phosphines, Benzynes, and CO: Facile Synthesis of Stable Zwitterionic Phosphonium Inner Salts.

The first synthesis of benzyne-derived stable zwitterions is reported. Benzynes generated from 2-(trimethylsilyl)aryl triflates undergo a multicomponent reaction with phosphines and CO to produce the stable 1,5-zwitterionic species in moderate to excellent isolated yields, which provides a novel method for the preparation of phosphonium inner salts under mild and transition-metal-free conditions.