Efficient Ring Closing Metathesis by NHC-Supported (Arylimido)vanadium(V)-Alkylidene Catalysts Containing Perhalophenoxide Ligands: Exclusive RCM under High Substrate Concentration

Ring closing metathesis (RCM) reactions of N,N-diallyl-4-toluenesulfonamide (S1) and N,N-diallylaniline (S2) by V(N-2,6-Cl2C6H3)(CHSiMe3)(OC6X5)(NHC) [X = F, Cl (4), Br (5); NHC = 1,3-bis(2,6-dimethylphenyl)imidazole-2-ylidene (IXy)] exclusively afforded the corresponding ring closed products (yields 83 to >99%) under high initial substrate concentration conditions (3.2–24 M). A significant increase in the activity was observed upon increasing the substrate concentrations, leading to highly efficient RCM [RCM of S2 by 4,5: TON = >1000, TOF = >100 s–1, yield (conv.) 95 to >99%]. The RCM of diallyl ether and diallyl thioether afforded the corresponding ring closed products exclusively, whereas the activities increased with dilution of the substrate concentrations. The RCM of 1,7-octadiene also gave cyclohexene.