Chiral lewis Acid catalysis in nitrile oxide cycloadditions.
We describe examples of highly regio- and enantioselective nitrile oxide cycloadditions to unsaturated alkenes using substoichiometric amounts of a chiral Lewis acid. Pyrazolidinones proved to be effective achiral templates in the cycloadditions providing C-adducts typically in >30:1 selectivity and 80-99% ee. To avoid potential problems involving coordination of the Lewis acid by amine bases, we have devised a novel method for the generation of unstable nitrile oxides from hydroximinoyl chlorides using Amberlyst 21 as the base.
Sibi
Mukund P
MP
Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105, USA. Mukund.Sibi@ndsu.nodak.edu
Itoh
Kennosuke
K
Jasperse
Craig P
CP