Modification of Supported and Unsupported Nickel Catalysts by α-Amino and α-Hydroxy Acids for Chiral Reactions

Abstract

The use of heterogeneous metal catalysts to effect asymmetric reactions is not new, dating back to work in the 1930's by Schwab [1,2] and by Lipkin and Stewart [3]. However, it is only in the past 20 years that the subject has been studied in any detail.

The requirement of asymmetric activity is the existence of a chiral environment on the catalyst surface and this may be created in one of two ways. First, by supporting the metal on a chiral support and second, by adsorption of a chiral modifier on the active phase of a conventional metallic catalyst. Whilst examples of both approaches are extant, the latter approach is the which has been more commonly used.

Whilst as detailed in the recents reviews by Blaser [4] and Blaser and Muller [5], many reactions have been identified, only two systems have been subjected to detailed study, both of which have used the approach of modifying the catalyst by the adsorption of a chiral modifier. These systems are (a) modification of nickel catalyst, usually Raney Ni, by α-hydroxy or α-amino acids and (b) modification of platinum catalyst with the cinchona alkaloid derivatives.