A new route to cyclopentenones via ruthenium-catalyzed carbonylative cyclization of allylic carbonates with alkenes

[GRAPHICS] [RuCl2(CO)(3)](2)/Et3N (eta(3)-C3H5)RuBr(CO)(3)/Et3N are highly effective c atalyst systems for carbonylative cyclization of allylic carbonates with al kenes to give the corresponding cyclopentenones in high yields. For example , treatment of allyl methyl carbonate (1a) with 2-norbornene (2a) in the pr esence of a catalytic amount of [RUCl2(CO)(3)](2) (2.5 mol %) and Et3N (10 mol %) at 120 degrees C for 5 h under 3 atm of carbon monoxide gave the cor responding cyclopentenone, exo-4-methyltricyclo[5.2.1.0(2,6)]dec-4-en-3-one (3a), in 80% yield with high stereoselectivity (exo 100%).