Synergistic photoredox and tertiary amine catalysis: generation of allylic sulfones from Morita–Baylis–Hillman acetates and sulfur dioxide

The first example of the synthesis of allylic sulfones through synergistic photoredox and tertiary amine catalysis, starting from MBH acetates, DABCO·(SO 2 ) 2 and 4-substituted Hantzsch esters or potassium alkyltrifluoroborates via a radical pathway, is reported. A wide range of allylic sulfones can be easily obtained in moderate to excellent yields. Mechanistic studies show that synergistic photoredox and tertiary amine catalysis is essential for this successful transformation with the insertion of sulfur dioxide.