Synthesis of 2-Sulfonyl Carbazoles via Oxidative C-H Functionalization of Tetrahydrocarbazoles with Sulfonyl Hydrazides.

Herein, we report an approach for the synthesis of 2-sulfonyl carbazoles from the oxidative C-H sulfonylation of tetrahydrocarbazoles. The mechanistic study reveals that this special selectivity is realized by the addition of a sulfonyl radical to the 3,4-dihydrocabazole intermediate via dehydrogenative desaturation of tetrahydrocarbazoles. This approach features readily available starting materials, high regioselectivity, broad substrate scope, and attractive synthetic utility.