In situ generation and protonation of the isocyanide/acetylene adduct: a powerful catalyst-free strategy for multicomponent synthesis of ketenimines, aza-dienes, and heterocycles

In addition to isocyanide-based Ugi, Passerini, van Leusen, and Orru multicomponent reactions, a new class of isocyanide/acetylene-based multicomponent reactions, using zwitterionic adducts, have emerged as powerful methods to synthesize biologically interesting molecules.