Mechanistic studies of the photocatalytic three-component ring-opening reaction of 3-substituted-1-azabicyclo[1.1.0]butanes towards 3,3-disubstituted N-sulfonylazetidines

In this work, we describe the mechanistic studies regarding the photocatalytic three-component ring-opening reaction of 3-substituted-1-azabicyclo[1.1.0]butanes, using sodium sulfinates and cyanopyridines, to prepare 3,3-disubstituted N-sulfonylazetidines. Using deuterium labelling experiments, fluorescence quenching to determine the Stern-Volmer constant (K_sv), TEMPO inhibition study, and literature comparison with related studies, we could propose the mechanism for the fundamental steps of the reaction. Specifically, we were able to gain insights into the competitive pathway that led to the formation of the hydrogenated byproduct 5. With this understanding, it is now possible to prevent or take advantage of this particular step to develop further applications of the photocatalytic ring-opening reaction of 1-azabicyclo[1.1.0]butanes (ABBs).