# Regioselective C2-Sulfonylation of Indoles and Pyrroles via SO2 Insertions

## TL;DR

A new chemical method efficiently creates C2-sulfonylated indoles and pyrroles using a cascade reaction under mild conditions.

## Contribution

A novel cascade reaction using molecular iodine catalysis and DABSO as an SO2 source for regioselective sulfonylation.

## Key findings

- The reaction provides C2-sulfonylated indoles and pyrroles in good to excellent yields.
- The cascade proceeds via an arylsulfonyl radical intermediate under mild conditions.
- The method shows a broad substrate scope and sustainability.

## Abstract

A molecular iodine-catalyzed three-component cascade
reaction of
indoles/pyrroles, anilines, and DABSO has been developed, providing
C2-sulfonylated indoles/pyrroles in good to excellent yields. The
transformation proceeds via the in situ generation
of the arylsulfonyl radical from the reaction of anilines,
t
BuONO, and DABSO, followed by controlled formation
of a carbon-centered radical intermediate. In this radical-mediated
cascade reaction, DABSO acts as the sulfone (SO2) source
while
t
BuONO facilitates the generation
of reactive species. Moreover, this one-pot transformation proceeds
under mild conditions, exhibits a broad substrate scope, and offers
an efficient and sustainable strategy for the construction of C2-sulfonated
indoles and pyrroles.