Related Experiment Video
Updated: Aug 19, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Control of enantioselectivity in catalytic metal carbene reactions
1Department of Chemistry, University of Arizona, Tucson 85721-0041, USA. mdoyle@u.arizona.edu
Abstract:
Chiral dirhodium(II) complexes constructed from 2-oxopyrrolidine, 2-oxazolidinone, N-acyl-2-imidazolidinone, or 2-azetidinone ligands are exceptional catalysts for enantioselective metal carbene transformations which provide lactones and lactams via cyclopropanation, cyclopropenation, C-H insertion, and ylide reactions with enantiomeric excesses greater than 90% and, usually, in very high yields. These chiral catalysts present high diastereo-, regio- and chemoselectivities, turnover numbers up to 1000, as well as recoverability and reuse.
Related Concept Videos
Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
Radical Anti-Markovnikov Addition to Alkenes: Overview
Stereochemical Effects of Enolization

