Recent advances in the catalytic asymmetric nitroaldol (Henry) reaction

Catalyst-controlled enantio selective nitroaldol (or Henry) reactions are presented. These reactions represent powerful CC bond-forming tools and the resulting nitro alcohol (nitroaldol) products can be transformed into a number of nitrogen- and oxygen-containing derivatives (nitroalkenes, amino alcohols, amino acids etc.). In addition to substrate-controlled nitroaldol reactions (not covered), catalytic systems that provide good stereoselectivity have been developed in recent years. Through the use of preformed silyl nitronates as activated substrates, catalytic systems involving metallic Lewis acids or tetraalkylammonium salts have been deployed in fluoride-mediated nitroaldol reactions. In a further advance, catalytic systems capable of promoting direct nitroaldol reactions between unmodified nitroalkanes and aldehydes (ketones) with high yields and stereoselectivities have been developed. To this end, ambifunctional systems based on La, Zn, Cu, Co and Mg metal species are described, together with some organocatalysts. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).