The facile synthesis of 2-bromoindoles via Cs2CO3-promoted intramolecular cyclization of 2-(gem-dibromovinyl)anilines under transition-metal-free conditions

Abstract

2-Bromoindoles were readily prepared through a facile Cs₂CO₃-promoted intramolecular cyclization of 2-(gem-bromovinyl)-N-methylsulfonylanilines in excellent yields under transition-metal-free conditions. This methodology could be extended to the synthesis of corresponding 2-chloroindoles. The reaction mechanism suggested that cyclization occurs through a key intermediate, phenylethynyl bromide, followed by cyclization in one-pot.