Syntheses of spiro-oxindoles via KI/oxone-mediated oxidation/cyclization of homotryptamine and homotryptophol derivatives

Oxidative cyclization of indoles is one of the most widely used approaches to exploit the synthetic utility of indoles. In continuation of our research interest in green oxidative cyclization of indoles with Oxone-halide. Here we report an oxidative cyclization of hometryptamine and hometryptophol derivatives using KI/oxone, enabling efficiently access to spiro-heterocyclic oxindoles incorporating tetrahydrofurans, pyrrolidines, pyranones, furanones, and lactams would be difficult to prepare by other methods. This protocol features mild reaction condition, green catalytic system, simple operation and broad substrate scope, which can be applied to various potential transformations.