Kinetic isotope effects for addition of lithium pinacolone enolate to benzaldehyde

The carbonyl-carbon-13 and phenyl-Dg kinetic isotope effects (KIEs) were measured for the reaction of benzaldehyde and lithium pinacolone enolate. The KIEs together with ab initio MO calculations indicated that a CC bond formation process is involved in the rate-determining transition state of the reaction. It was concluded that the enolate addition reaction proceeds in a different manner from those for MeLi and PhLi, for which the rate-determining step was judged to be an electron transfer step.