Green oxidative rearrangement of indoles using halide catalyst and hydrogen peroxide

Oxidative rearrangement of indoles is an essential transformation that has been widely used in the synthesis of many pharmaceutical agents and bioactive natural products. Herein, we report an efficient, practical and metal-free method for the oxidative rearrangement of indoles to spirooxindoles, 2-oxindoles, 2,2-disubstituted indolin-3-ones, and oxa-spirooxindoles using 10 mol% HBr and hydrogen peroxide as the terminal oxidant. The protocol displays a broad substrate scope (35 examples) and a wide range of functional group tolerance and has been applied in the synthesis of (+/-)-coerulescine and the formal synthesis of (+/-)-horsfiline. Notably, the distinct advantages of this protocol involve metal-free catalysis, waste prevention, and simple operation.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

This paper presents an efficient metal-free method for the oxidative rearrangement of indoles, leading to the formation of various organic compounds. The protocol exhibits a broad substrate scope and functional group tolerance, and has been successfully applied in natural product synthesis.