cupric acetylacetonate (Cu(acac)2) affords cyclopropyl trimethylsilylmethyl ketones. One-flask procedure for the formation of these silylated ketones and subsequent treatment with organometallics or with lithium diisopropylamide (LDA) and then carbonyl compounds gives a variety of vinylcyclopropanes or cyclopropyl vinylketones in good yields, respectively. Cycloaddition of 1-diazo-3-trimethylsilylpropanone
results in the formation of the corresponding silyl enolethers or β-ketosilanes. The relative ratio of these products varies with the ylide conditions and the stability of ylide used. It is noteworthy that silyl enolethers were formed under the salt-free ylide conditions, and that β-ketosilanes were yielded in the presence of soluble inorganic salts in THF, selectively. The formation of both products