Decarboxylative Bromooxidation of Indoles by a Vanadium Haloperoxidase

Halooxindoles are versatile building blocks for the construction of complex oxindole-containing targets of biological importance. Despite their synthetic value, catalytic methods to make 3-halooxindoles from readily available starting materials have remained undisclosed. We recently discovered that the chloroperoxidase from Curvularia inaequalis (CiVCPO) is a viable catalyst for the decarboxylative bromooxidation of 3-carboxyindoles to furnish 3-bromooxindoles with excellent regio- and chemoselectivity. In addition to the development of the synthetic method, this study provides evidence of a bromide recycling mechanism for the indole oxidation event. A discussion of the reaction development, substrate scope, mechanistic insights, and reaction applicability will be discussed herein.