Chiral calcium iodide for asymmetric Mannich-type reactions of malonates with imines providing β-aminocarbonyl compounds.

Out of the pybox: We have developed a novel chiral calcium iodide catalyst from CaI2 and a pybox that is stable under moisture and oxygen. This catalyst was applied to catalytic asymmetric Mannich-type reactions of malonates with both N-Boc-protected aromatic and aliphatic imines, and resulted in moderate to high yields with high enantioselectivities. To the best of our knowledge, this is the first example of highly enantioselective metal-catalyzed asymmetric Mannich-type reactions of malonates with N-Boc-protected aliphatic imines. The Mannich adduct was successfully converted into the α-hydroxy β-amino acid derivative. We have also shown the unique structure of the chiral Ca complexes with malonates.