2-Trimethylsilylmethylallyl acetate

Trimethylsilylmethylallyl acetate 307a, readily available from CH2— CMeCH20H, provides the equivalent of trimethylenemethane for cycloaddition to electron-deficient olefins in the presence of a (Ph3P)4Pd complex to give methylenecyclopentanes, normally in 50-85% yields... 

Some annulation reactions other than those described above have been found. Reaction of 4-ethyl-5-methyl-2-pyrone 509 (Scheme 93) with the trimethylenemethane palladium complex derived from 2-trimethylsilylmethylallyl acetate 307a gives the [4 + 3]-cycloadduct 510 in... 

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