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.