Asymmetric Cyclopropanations by Rhodium(II) <i>N</i>-(Arylsulfonyl)prolinate Catalyzed Decomposition of Vinyldiazomethanes in the Presence of Alkenes. Practical Enantioselective Synthesis of the Four Stereoisomers of 2-Phenylcyclopropan-1-amino Acid
作者:Huw M. L. Davies、Paul R. Bruzinski、Debra H. Lake、Norman Kong、Michael J. Fall
DOI:10.1021/ja9604931
日期:1996.1.1
to]dirhodium. The carbenoid structure has a critical effect on the degree of asymmetric induction, and the combination of a small electron-withdrawing group such as a methyl ester and an electron-donating group such as vinyl or phenyl resulted in the highest levels of enantioselectivity. The use of electron neutral alkenes and pentane as solvent also enhanced the enantioselectivity of the process.
Novel chiral dirhodium catalysts derived from aziridine and azetidine carboxylic acid for intermolecular cyclopropanation reactions with methyl phenyldiazoacetate
Three new chiraldirhodium(II) tetracarboxylate catalysts, based on azetidine- and aziridine-2-carboxylic acid, were prepared. Their selectivities in the cyclopropanationreaction of methylphenyldiazoacetate and olefins were determined in solvents of decreasing polarity and compared with those obtained with proline derived catalysts.