Visible-light-induced methylsulfonylation/bicyclization of C(sp3)-tethered 1,7-enynes using a DMSO/H2O system

A visible light photocatalytic methylsulfonylation/bicyclization of C(sp(3))-tethered 1,7-enynes has been established using a dimethyl sulfoxide (DMSO)/H2O system as the methylsulfonyl source. This reaction worked readily to access a wide range of sulfone-containing benzo[a]fluoren-5-ones with one quaternary carbon centre and generally good yields through C-S bond cleavage of DMSO. The reaction mechanism was proposed based on the control experiments.