Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis

Lewis
acids are frequently employed in catalysis but they often
suffer from high moisture sensitivity. In many reactions, catalysts
are deactivated because of the problem that strong Lewis acids also
bond to the products. In this research, hydrolytically stable bidentate
Lewis acid catalysts derived from selenonium dicationic centers have
been developed. The bis-selenonium catalysts are employed in the activation
of imine and carbonyl groups in various transformations with good
yields and selectivity. Lewis acidity of the bis-selenonium salts
was found to be stronger than that of the monoselenonium systems,
attributed to the synergistic effect of the two cationic selenonium
centers. In addition, the bis-selenonium catalysts are not inhibited
by strong bases or moisture.