Tf2O-Mediated One-Pot Synthesis of 3-Substituted Thiochromones via Sequential Activation of Thioesters and Carboxylic Acids

Abstract

A triflic anhydride (Tf₂O)-mediated annulation of thioesters with carboxylic acids, providing a direct route to thiochromones and 3-acylthiochromones, has been reported. The transformation proceeds through a sequential activation, wherein Tf₂O facilitates intramolecular Friedel–Crafts-type cyclization of the thioester to produce the thiochromone scaffold, while simultaneously activating the carboxylic acid to generate a reactive acylium intermediate, enabling regioselective electrophilic acylation at the C-3 position. This tandem cyclization–acylation sequence provides a general platform for constructing structurally diverse thiochromones.