Asymmetric Henry reaction catalysed by transition metal complexes: A short review

An asymmetric Henry reaction, the coupling of a nitro alkane and a carbonyl group is an important C-C bond forming reaction in organic chemistry giving chiral nitro alkanols which are useful versatile intermediates in synthetic organic chemistry. It is well known that the chiral nitroaldol products find increasing applications in the pharmaceutical industry. These converted products are important precursors of biologically active compounds. Chiral nitroalcohols can be further transformed into synthetically useful derivatives such as carboxylic acids, polyamino alcohols, polyhydroxylated amides and amino alcohols. For the catalytic asymmetric Henry reaction, among the catalysts reported so far, the transition metal complexes catalyse asymmetric Henry reaction plays an important role. Transition metal complexes catalyse the asymmetric Henry reaction efficiently and in most of the cases give the product chiral nitro alkanols in good yield and enantiomeric excess. This review summarizes the reported remarkable transition metal complex catalysts for asymmetric Henry reaction, their advantages, limitations, mechanism for their catalytic activity and the challenges that need to be addressed in this research area.