Solvent effects on the asymmetric Pauson-Khand-type reaction by rhodium

Abstract

The reaction efficiency and enantioselectivity of an asymmetric Pauson-Khand-type reaction catalyzed by cationic rhodium are heavily dependent on the solvent. Coordinating solvents, such as THF, provide a faster reaction and better stereoselectivity than non-coordinating solvents, such as toluene. These beneficial effects can be attributed to a significant increase in the more reactive catalytic species of [Rh(bisphosphane ligand)*(solvent)(n)](+) (3) than of [Rh(bisphosphine ligand)*CO(solvent)](+)(4) and [Rh(bisphosphine ligand)*(CO)(2)](+) (5) in a coordinating solvent. (C) 2009 Elsevier Ltd. All rights reserved.