Stitching β‐Ketothioamides with N‐Tosylbenzoquinone Imine: Transition‐Metal Free Site‐Selective Domino Synthesis of 2‐Amino‐3‐aroyl‐5‐sulfonamide Substituted Benzo[b]furans

Benzofuran derivatives are core components in many biologically active natural and synthetic compounds including approved drugs. Herein, an easy‐to‐access and TM‐free, one‐pot, three‐step synthesis of 2‐amino‐3‐aroyl‐5‐sulfonamide substituted benzo[ b ]furans bearing many functional groups of different electronic and steric nature using thioamides (as a 2C synthon) and N ‐tosylbenzoquinone imine (as a CCO unit partner) at room temperature in open air is presented for the first time. The reaction proceeds via deprotonation/Michael addition/cyclization/aromatization cascades forming two new (CC and CO) bonds and one ring, liberating only H 2 S as a byproduct. High resolution mass spectrometry study endorses the key intermediates involved during reaction, validating excellent regio‐ and chemoselectivity. This protocol will not only provide an efficient and scalable method to access diverse benzo[ b ]furans that could be adaptable to late‐stage functionalization but also enrich the research domain of thioamides.