Scope and post-transformations for the borane-isocyanide multicomponent reactions: Concise access to structurally diverse heterocyclic compounds

Abstract

A recently described family of multicomponent reactions (MCRs) involving isocyanides, aldehydes, dipolarophiles and alkylboranes that yield highly substituted aziridines, oxazolidines and pyrrolidines has been studied in detail. In this work the scope of these processes is significantly increased by preparing the borane input through hydroboration of alkenes or organometallic processes, in tandem with the MCR. The aldehyde range is also expanded, and indole-3-carbaldehydes yield reactive imines and bis-indolyloxazolidines, depending on the electron density of the heterocycle. Finally, the obtained adducts constitute an ideal platform to generate structurally diverse compounds using simple post-condensation modifications. In this way, indole imines undergo stereoselective hydrocyanation and oxazolidines are reductively opened to give amino alcohols. Additionally, palladium-, ruthenium- and gold-catalyzed processes lead to a variety of complex heterocycles. The methodology is simple, efficient and highly divergent, leading to an array of interesting scaffolds for medicinal chemistry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.