Directed Catalytic Asymmetric Olefin Metathesis. Selectivity Control by Enoate and Ynoate Groups in Ru-Catalyzed Asymmetric Ring-Opening/Cross-Metathesis

A new concept in catalytic asymmetric olefin metathesis is introduced: a nonreacting enoate or ynoate group can be used to alter and significantly enhance the enantioselectivity. Catalytic asymmetric ring-opening/cross-metathesis (AROM/CM) processes proceed in ≤30% ee with non-styrenyl cross partners. However, with olefin partners bearing an enoate or ynoate group (1,6-diene or 1,6-enyne), catalytic AROM/CM affords the desired products in up to 98% ee, with the opposite sense of enantioselectivity versus reactions with styrene or aliphatic cross partners. This new method, for the first time, extends the scope of effective metal-catalyzed AROM/CM to reactions of non-styrenyl alkenes and cyclopropenes, a diverse and readily available set of substrates, and that of Ru-catalyzed asymmetric olefin metathesis to include processes that bear all-carbon quaternary stereogenic centers.