Generation of sulfonated 1-isoindolinones through a multicomponent reaction with the insertion of sulfur dioxide

A four-component reaction of 2-vinylbenzoic acids, aryldiazonium tetrafluoroborates, the sulfur dioxide surrogate DABCO(SO2)(2), and nitriles under photocatalysis in the presence of visible light is developed. This multicomponent reaction works efficiently, promoted by BF3OEt2 with the insertion of sulfur dioxide under mild conditions, leading to sulfonated 1-isoindolinones in moderate to good yields. This route is highly selective, and several competitive pathways are not observed under these conditions. A possible mechanism involving photocatalysis and a Lewis acid is proposed.