Solvent enhancement of reaction selectivity: a unique property of cationic chiral dirhodium carboxamidates.

ABSTRACT: 1,3-Dipolar cycloaddition reactions of nitrones with α,β-unsaturated aldehydes catalyzed by a cationic chiral dirhodium(II,III) carboxamidate with (R)-menthyl (S)-2-oxopyrrolidine-5-carboxylate ligands in toluene increase reaction rates, give optimum regioselectivities, and enhance stereoselectivities compared to the same reactions performed in traditionally used halocarbon solvents. Rate and enantioselectivity enhancements were also obtained in hetero-Diels-Alder and carbonyl-ene reactions performed in toluene over those obtained in dichloromethane using the diastereomeric chiral cationic dirhodium(II,III) carboxamidate with (S)-menthyl (S)-2-oxopyrrolidine-5-carboxylate ligands. These enhancements are attributed to diminished or absent association of toluene with the catalyst which lesse

SUBMITTER: Wang X 

PROVIDER: S-EPMC3116040 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature