Critical solvent effect on the chiral recognition of a catalytic species by a chiral substrate

In the diastereoselective cyclocarbonylation of isopulegol and isolimonene catalysed by the non-chiral [PdCl 2 L 2 ] palladium complexes (L = PPh 3 , L 2 = bis(diphenylphosphino)-butane or -ferrocene), the diastereoisomeric excess is enhanced by a factor of 1.5–2 when toluene is substituted by chloro-solvents. A less significant effect is noted when using more coordinating solvents such as acetonitrile and THF. In chloro-solvents reaction rates are faster than in toluene, isopropanol, acetonitrile or THF.