Regio-and diastereoselectivity studies on the photocycloaddition of ketene diethyl acetal to chiral 2(5H)-furanones

The photochemical [2+2] cycloaddition of 1,1-diethoxyethylene to chiral 2(5H)-furanones is investigated. The effect of the substituents of the lactone and the polarity of the solvents on the chemical yield, regioselectivity, and facial diastereoselectivity is evaluated. The reactions in ether proceed with excellent regioselectivity and good yields. Hydrolysis of the ketal group of the major cycloadducts afforded enantiopure cyclobutanones fused to γ-lactones.