Synthesis of medium-sized benzo[b]azocines and benzo[b]azonines by photoinduced 8-/9-endo sulfonyl-cyclization

An efficient photochemical radical sulfonyl cyclization of designed dienes to medium-sized benzo[b]azocines and benzo[b]azonines was developed.This chemoselective method provides new highly functionalized eight-and nine-membered N-heterocycles.Radical inhibition experiments,light on/off experiments,and apparent quantum efficiency calculations were used to clarify the radical mechanism.Density functional theory calculations enabled rationalization of the rate-determining step and observed chemoselectivity.Large-scale synthesis and derivatizations via epoxidation and convenient N-Ts deprotection showed the potential utility of this strategy.This photochemical method for synthesizing sulfonylbenzo[b]azocines and sulfonylbenzo[b]azonines with insertion of sulfur dioxide provides new sustainable routes for the synthesis of valuable medium-sized Nheterocycles.