Brønsted acid catalyzed remote C6 functionalization of 2,3-disubstituted indoles with β,γ-unsaturated α-ketoester

Abstract

A metal-free catalytic approach for the remote C6-functionalization of 2,3-disubstituted indoles has been developed. In the presence of catalytic amounts of Brønsted acid, the β,γ-unsaturated α-ketoesters react with 2,3-disubstituted indoles at the C6 position selectively. Under mild reaction conditions, a range of C6-functionalized indoles were prepared with good yields and excellent regioselectivity. This methodology provides a concise and efficient route for the synthesis of C6-functionalized indole derivatives.

Brønsted acid-catalyzed C6 functionalization of 2,3-disubstituted indoles for construction of cyano-substituted all-carbon quaternary centers

“…2 Owing to the inherently nucleophilic properties, the C–H functionalization of indoles at the remote C6-position becomes challenging. As chemists devoted continuous efforts for C6 functionalization of indoles, several directly catalytic protocols have been developed to construct tertiary carbon centers 3 and quaternary carbon centers. 4 Brønsted acid-catalyzed, Lewis acid-catalyzed and rhodium-catalyzed direct C6 functionalizations of indoles were disclosed for the formation of tertiary carbon centers.…”