Chiral Tetra-coordinate Aluminum Cation in Catalysis

Although the application of cationic aluminum complexes in catalysis has been extensively investigated, the incorporation of an aluminum cation into a chiral environment is less explored. In this study, a C2-symmetric chiral tetra-coordinate aluminum cation [3]+ bearing two chiral amino alcohol-derived ligands was prepared from commercially available starting materials in two steps. The high Lewis acidity of [3]+ exceeding that of B­(C6F5)3 was verified by a competition binding experiment. Preliminary catalytic activity studies of [3]+ revealed that the tetra-coordinate aluminum cation is effective in accomplishing high conversion in all cases. However, the presence of a labile N–Al bond diminishes the enantioselectivity of the activation process.