In a glovebox, an oven dried screw-capped 2 mL vial was charged with a magnetic stir bar, Ni(COD)2 (10 μmol) , carbene ligand Me IPr tBu (10 μmol), degassed (free pump thaw) THF (0.1 mL) was then added and the catalyst mixture was stirred at room temperature for 30 min, during which a red black solution is formed. Ketone (0.1 mmol degassed freeze pump thaw if the ketone is liquid) and COD (0.15 mmol degassed by freeze pump thaw) was then added successively. The vial was sealed with a Teflon-lined screw cap, and taking out of glovebox, then H2O or MeOH (10 μmol)) was added under Schlenk line. After 24 h, the reaction mixture was diluted with dichloromethane and filtered through a plug of silica gel. After evaporated the solvent, the mixture was analysed by crude NMR.