An electron donor-acceptor (EDA) complex-mediated oxidative radical addition/cyclization between o-cyanoarylacrylamides and thiosulfonates has been accomplished, providing direct access to sulfonylated quinoline-2,4(1H,3H)-diones. Mechanistic investigations suggest the EDA complexation between Et3N and thiosulfonate, followed by the in situ generation of R-SO2 radical, which adds to o-cyanoarylacrylamides. This is followed by cyclization, abstraction of a hydrogen atom from H2O, and imine hydrolysis to a keto group.
Manna et al. (Tue,) studied this question.