11 February 2022

Intermolecular Photocatalytic Chemo-, Stereo- and Regioselective Thiol-yne-ene Coupling Reaction

The first example of an intermolecular thiol–yne–ene coupling reaction is reported for the one-pot construction of C?S and C?C bonds. Thiol–yne–ene coupling opens a new dimension in building molecular complexity to access densely functionalized products. The employment of Eosin Y/DBU/MeOH photocatalytic system suppresses hydrogen atom transfer (HAT) and associative reductant upconversion (via C?S three-electron ?-bond formation). Investigation of the reaction mechanism by combining online ESI-UHRMS, EPR spectroscopy, isotope labeling, determination of quantum yield, cyclic voltammetry, Stern–Volmer measurements and computational modeling revealed a unique photoredox cycle with four radical-involving stages. As a result, previously unavailable products of the thiol–yne–ene reaction were obtained in good yields with high selectivity. They can serve as stable precursors for synthesizing synthetically demanding activated 1,3-dienes.

Reference: Angew. Chem. Int. Ed., 2022, ASAP

DOI: 10.1002/anie.202116888