Density functional theory (DFT) computations (B3LYP and M06) were performed to elucidate the mechanism of a Z-selective asymmetric ring-opening/cross-metathesis reaction catalyzed by a ruthenium complex with an N-heterocyclic carbene (NHC)–admantyl chelator (1cat). The reaction was also enantioselective because the catalyst employed was chiral and stereogenic at the ruthenium center. The system that has been computed consists of the full sets of the catalyst and allyl acetate substrate, as well as a truncated model for the norbornene substrate. The initial metathesis of 1cat with allyl acetate via a side-bound pathway yields two active catalytic species, which lead to the final Z- and E-products, respectively. The high enantioselective excess of both Z- and E-isomers originates from the steric hindrance imparted by the incoming norbornene substrate, which only has one favorable approach out of four possible orientations.

Computational insight into origins of Z-selectivity and enantioselectivity of asymmetric ring-opening/cross-metathesis catalyzed by a stereogenic-at-Ru complex

249th National Meeting (2015)

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