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

reaction: see text]2-(Triisopropylsilyloxy)acrolein is easily prepared by the reaction of triisopropylsilyl triflate and 2-methoxy-2-methyl-1,3]dioxan-5-one in the presence of triethylamine. This dienophile reacts with selected dienes in the presence of catalytic amounts of scandium triflate to afford products that are formally 4 + 3 cycloadducts. An exception is seen in the case of butadiene, where only a 4 + 2 cycloadduct is observed.