Synthesis of spirocyclic β-methylene-γ-lactone utilizing hydroxymethylation of functionalized allylsilane

A new spiro-β-methylene-γ-lactone annulation reaction is addressed for the synthesis of 4-methylene-2-oxaspiro[4.5]decan-1-one and its derivatives. 2-Cyclohexylidene-3-trimethylsilylprop-1-yl pivalate, obtained from cyclohexanone, was hydroxymethylated followed by desilylation to afford 2-[(1-hydroxymethyl)cyclohexyl]prop-2-en-1-yl pivalate and its -1-en-1-yl isomer. The former was oxidized to carboxylic acid followed by lactonization to the above compound. It was found that the stereochemistry of the hydroxymethylation reaction depends on the substituent on the cyclohexane ring.