On the stability of the π-allyl intermediate in molybdenum-catalyzed asymmetric alkylations

Density functional theory calculations were performed on the apparent [eta]3-[pi]-allyl molybdenum intermediate that is observed during molybdenum-catalyzed asymmetric allylation [Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 5379]. The relative stabilities of geometric isomers, diastereoisomers, and [pi]-allyl rotamers of the [pi]-allyl molybdenum intermediate were investigated. Calculations show that the observed intermediate is the most stable because of two factors: (1) the observed [pi]-allyl molybdenum intermediate maximizes the bonding and back-bonding interactions between molybdenum and the [pi]-allyl ligand; and (2) the observed [pi]-allyl molybdenum intermediate minimizes the steric interactions between the chiral ligand and the [pi]-allyl group.