Selective sulfonylation and diazotization of indoles.

A metal-free synthesis of bifunctionalized indole derivatives was developed through a novel TBHP/TBAI-mediated oxidative coupling of C2,C3-unsubstituted indoles with arylsulfonyl hydrazide. Under the same conditions C3-methyl substituted indoles underwent a diazotization process, affording 2-sulfonyldiazenyl-1H-indoles. The former reaction simultaneously established C-S and C-N bonds through selective sulfonylation and diazotization of the indole framework, enabling a mild and practical access to polyfunctionalized indoles with good to excellent yields.