Enantioselective aza-Henry reaction using cinchona organocatalysts

The aza-Henry reaction of imines with nitromethane was promoted by cinchona alkaloids and modified cinchona bases to give optically active beta-nitroamines. Various N-protected imines were examined as substrates. N-Boc, N-Cbz, and N-Fmoc protected imines gave the best results in terms of chemical yields and enantioselectivities. After a careful screening of a series of chiral bases, very good enantioselectivities up to 94% ee were obtained using a cinchona-based thiourea organocatalyst under the optimized reaction conditions. (c) 2005 Elsevier Ltd. All rights reserved.