Tf ₂ O‐Mediated One‐Pot Synthesis of 3‐Substituted Thiochromones via Sequential Activation of Thioesters and Carboxylic Acids

ABSTRACT

A triflic anhydride (Tf ₂ O)‐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 Tf ₂ O 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.