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One-Pot Synthesis of 2,4-Diacyl Thiophenes from α-Oxo Ketene Dithioacetals and Propargylic Alcohols.

Although thiophenes having various functionalities are the basic structural units in numerous bioactive compounds and optoelectronic materials, synthetic routes to acylated thiophenes from aliphatic sulfur-containing starting materials are still rare. In particular, there have been no reports concerning the straightforward synthesis of 2,4-diacylthiophenes from alkynes. Herein, we describe a highly efficient and metal-free three-step one-pot synthetic approach to tetrasubstituted 2,4-diacylthiophenes from propargylic alcohols and α-oxo ketene dithioacetals. This research features a relay catalysis system that integrates Brønsted acid-catalyzed propargylation, molecular iodine-mediated electrophilic cyclization and visible light-induced deiodinative oxygenation. The 2,4-diacylthiophenes serving as the key starting materials are readily synthesized, enabling facile construction of analogues of related biologically active compounds and the modular assembly of tetrasubstituted thienothiophenes.