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

Density functional theory calculations were performed on the apparent η3-π-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 π-allyl rotamers of the π-allyl molybdenum intermediate were investigated. Calculations show that the observed intermediate is the most stable because of two factors: (1) the observed π-allyl molybdenum intermediate maximizes the bonding and back-bonding interactions between molybdenum and the π-allyl ligand; and (2) the observed π-allyl molybdenum intermediate minimizes the steric interactions between the chiral ligand and the π-allyl group.

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