Iodine radical mediated cascade [3 + 2] carbocyclization of ene-vinylidenecyclopropanes with thiols and selenols via photoredox catalysis

Abstract

An iodine radical mediated cascade [3 + 2] carbocyclization of ene-vinylidenecyclopropanes with thiols and selenols via photoredox catalysis has been reported in this paper. With this visible light-induced photocatalytic protocol, an efficient synthetic methodology for the rapid construction of sulfur- and selenium-containing polycyclic derivatives in moderate to good yields has been realized with broad substrate scope. Mechanistic investigations were also performed using control experiments, deuterium labeling and Stern–Volmer analysis as well as DFT calculations, suggesting that this cascade cyclization reaction stems from an iodine radical addition to the allenyl moiety of ene-vinylidenecyclopropane along with a cascade cyclization. Then, the reaction proceeds through a cyclopropane-ring opening pathway along with a HAT process and an intramolecular substitution. Further transformation of the obtained product has also been disclosed.