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.