Photoredox-catalyzed cascade [2 + 2 + 1] cyclization of 1,6-enynes with thiols†
Abstract
Here, we report a visible-light-mediated [2 + 2 + 1] cascade cyclization of 1,6-enynes with thiols, providing a new synthetic protocol for the rapid construction of sulfur-containing polycyclic derivatives in moderate to good yields along with a broad substrate scope. Mechanistic investigations were also performed through control experiments and Stern–Volmer analysis as well as DFT calculations, suggesting that this cascade cyclization reaction stems from a sulfur radical addition to the alkynyl moiety of 1,6-enyne along with a cascade cyclization with the alkenyl unit. Then, the formation of sulfur-containing polycyclic molecules can be achieved by homolytic SHi-type substitution at the thioether unit, stripping away a sulfur atom. Further transformations of the obtained product have also been disclosed.