Synthesis of Vinylcyclopropanes, Cyclopropyl Vinyl Ketones, and 3-Pyrazolyl Vinyl Ketones from 1-Diazo-3-trimethylsilylpropanone
Reaction of 1-diazo-3-trimethylsilylpropanone with olefins in the presence of 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 vinyl ketones in good yields, respectively.Cycloaddition of 1-diazo-3-trimethylsilylpropanone with acetylenes and similar carbon-carbon bond formation at the side chain of the cycloadducts lead to 3-pyrazolyl vinyl ketones.
Reaction of acylsilanes with sulfur ylides. Selective formation of silyl enol ethers or β-ketosilanes
The reaction of acylsilanes with sulfur ylides in THF results in the formation of the corresponding silyl enol ethers 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 enol ethers 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 would be interpreted in terms of the anionotropic and cationotropic rearrangements of silyl group in the reaction intermediate.