Sulfonium and Selenonium Salts as Noncovalent Organocatalysts for the Multicomponent Groebke–Blackburn–Bienaymé Reaction

Sulfonium and selenonium salts, represented by S-aryl dibenzothiophenium and Se-aryl dibenzoselenophenium
triflates, were found to exhibit remarkable catalytic activity in
the model Groebke–Blackburn–Bienaymé reaction.
Kinetic analysis and density functional theory (DFT) calculations
indicated that their catalytic effect is induced by the ligation of
the reaction substrates to the σ-holes on the S or Se atom of
the cations. The experimental data indicated that although 10-fold
excess of the chloride totally inhibits the catalytic activity of
the sulfonium salts, the selenonium salt remains catalytically active,
which can be explained by the experimentally found lower binding constant
of the selenonium derivative to chloride in comparison with the sulfonium
analogue. Both types of salts exhibit lower catalytic activity in
the model reaction than dibenziodolium species.