Self-assembly of an organocatalyst for the enantioselective synthesis of Michael adducts and alpha-aminoxy alcohols in a nonpolar medium

A proline-thiourea host-guest complex is described as a self-assembled organocatalyst for the enantioselective Michael addition of aldehydes to nitroolefins and for the asymmetric alpha-aminoxylation of both aldehydes and ketones. The Michael adducts were obtained in good yields of up to 80%, high diastereo-selectivities of up to 5:95, and high enantiomeric excesses of up to 98%. The optically active aminoxy alcohols were synthesized in 60-85% yields with 94-99% enantiomeric excesses after reduction of the alpha-oxidation products using NaBH4. (C) 2013 Elsevier Ltd. All rights reserved.