Asymmetric ring-closing metathesis catalyzed by chiral molybdenum alkylidene complexes

Kinetic resolution was observed in ring-closing metathesis of racemic dienes catalyzed by the newly developed chiral molybdenum alkylidene complexes (R,R)-Mo(CHCMe2Ph)(NAr)(TBEC) 1 (Ar = 2,6-i-Pr2C6H3, TBEC = 2',2',2 ",2 "-tetrakis(trifluoromethyl)-1,2-bis(2'-hydroxyethyl)cyclopentane) and (R,R)-Mo(CHCMe2Ph)(NAr)(TBEH) 2 (Ar = 2,6-i-Pr2C6H3, TBEH = 2',2',2 ",2 "-tetrakis(trifluoromethyl)-1,2-bis(2'-hydroxyethyl)cyclohexane). In the case of a prochiral symmetric triene substrate, optically active cyclized product was formed by catalytic ring-closing metathesis with 1, which opens the possibility of a new version of two-directional synthesis. Although the observed enantiomeric excesses were modest to low, this data demonstrates the feasibility of asymmetric induction by chiral alkylidene catalysts in ring-closing metathesis.