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.