Photoredox Polychloroalkylation/Spirocyclization of Activated Alkynes via C(sp3)-H bond Cleavage

A novel strategy of visible-light photoredox catalysis ipso-annulation of activated alkynes with polychloroalkanes for the synthesis of 3-polychloroalkyl spiro[4,5]trienones, which used 4-methoxybenzenediazonium tetrafluoroborate salt as a hydrogen atom transfer reagent, is described. This polychloroalkylation/ spirocyclization of alkynes offers a widely range of 3-polychloroalkyl-spiro[4,5]trienone derivatives in high yields with a broad substrate scope via selective C(sp(3))-H homolytic cleavage. The results of controlled experiments showed that this method involves a radical process. The polyhaloalkyl radical species generated from intermolecular hydrogen atom transfer (HAT) between aryl radical and polychloroalkanes.