Recent advances in isocyanide insertion chemistry.

As valuable C1 building blocks, isocyanides represent an important class of reactive species and synthons. During the past decades, exhaustive efforts have been devoted to the discovery of highly efficient reactions involving isocyanide on the basis of the development of the Passerini and Ugi reactions. Several types of reactions involving isocyanides have been reported, such as nucleophilic attack, electrophilic addition, imidoylation reactions, and oxidation etc. In this review, recent progress in isocyanide insertion chemistry is presented. Among all isocyanide insertions, two catalytic systems have been developed, that is, Lewis (Brønsted) acid-catalyzed isocyanide insertions and transition-metal-enabled isocyanide insertions, respectively. This review is hence written in the sequence of Lewis (Brønsted) acid-catalyzed isocyanide insertion and transitional metal-enabled isocyanide insertion, where isocyanide insertion into heteroatom-hydrogen bonds, carbon-halogen bonds, carbon-hydrogen bonds, and metal carbenes are summarized.