8-Methylene-1,4-dioxa-spiro[4.5]decane

Add BuLi to a solution of methyl triphenylphosphonium bromide in THF at -78° C. Stir this suspension for 10 min at -78° C, then 30 min at 0° C. Cool the orange solution obtained to -78° C, and add a solution of the monoethylene ketal of 1,4-cyclohexanedione in THF. Stir the reaction mixture overnight at room temperature (RT), then filter on Celite. Rinse the solid with pentane. After evaporating the solvents, the residue on the silica gel was chromatographed. 8-Methylene-1,4-dioxa-spiro[4.5]decane is thus obtained (colorless oil).