A Sulfonylation Reaction: Direct Synthesis of 2-Sulfonylindoles from Sulfonyl Hydrazides and Indoles

A metal-free synthesis of 2-sulfonylindole derivatives has been developed through a novel TBHP/I₂-mediated coupling of C3/unsubstituted indoles with sulfonyl hydrazides. The reaction utilizes readily available starting materials under mild reaction conditions, providing an alternative and attractive approach to 2-sulfonylindoles with high yields. The developed synthetic procedure is suitable for both N-protected or unprotected indoles.