Asymmetric phase-transfer catalysts bearing multiple hydrogen-bonding donors: highly efficient catalysts for enantio- and diastereoselective nitro-mannich reaction of amidosulfones.

Bifunctional asymmetric phase-transfer catalysts bearing multiple hydrogen-bonding donors have rarely been explored. The first quaternary ammonium type of these catalysts derived from cinchona alkaloids were readily prepared and found to be highly efficient catalysts for asymmetric nitro-Mannich reactions of amidosulfones. Compared with previous reports, very broad substrate generality was observed, and both enantiomers of the products were achieved in high enantio- and diastereoselectivity (90-99% ee, 13:1 to 99:1 dr).