Atom-economic metal free mediated difunctionalization of isocyanides with 3-methyleneoxindoles and 3-methylene-benzofuranones†

Isocyanides are an important class of building blocks in synthetic organic chemistry; however, the difunctionalization of isocyanides still presents significant challenges. Herein, we have developed metal free mediated difunctionalization of isocyanides with 3-methyleneoxindoles via the cleavage of the chemically inert carbon–nitrogen bond, which simultaneously allows for the formation of two carbon–carbon bonds and one carbon–nitrogen bond in one step. A series of functionalized polycyclic indoline skeletons were obtained in up to 93% yield under thermal conditions. Intriguingly, this protocol could also be extended to 3-methylenebenzofuranones, giving rise to three-dimensional indole fused bicyclo[3.2.1]octane through the cleavage of the carbon–oxygen bond. The theoretical calculation studies provided guidance on the in-depth insight into the mechanistic underpinnings of this cascade reaction.