Radical substituent effects of alpha-sulfonium groups

Alpha-sulfonium groups are radical stabilizing rather than radical destabilizing, as gleaned from theoretical calculations in an examination of the radical substituent effects of the alpha-sulfonium groups. Results showed that the radical-stabilizing effects of the alpha-dialkylsulfonium groups are smaller and with larger steric hindrance than those for the alpha-RS groups. They were also found to be associated with the free lone pair electrons of the sulfur atom in the sulfonium groups. The latter were found to be able to form a two-center three-electron bond with the unpaired electron of the radical.