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

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.