Synthesis and some cycloaddition reactions of 2-(triisopropylsilyloxy)acrolein

[GRAPHICS] 2-(Triisopropylsilyloxy)acrolein is easily prepared by the reaction of trii sopropylsilyl triflate and 2-methoxy-2-methyl-[1,3]dioxan-5-one in the pres ence of triethylamine. This dienophile reacts with selected dienes in the p resence of catalytic amounts of scandium triflate to afford products that a re formally 4 + 3 cycloadducts. An exception is seen in the case of butadie ne, where only a 4 + 2 cycloadduct is observed.