The Michael Reaction of Silyl Enol Ethers with α,β-Unsaturated Eetones and Acetals in the Presence of Titanium Tetraalkoxide and Titanium Tetrachloride
Silyl enol ethers react with α,β-unsaturated ketones and esters in the presence of TiCl4 or in the coexistence of TiCl4 and Ti(Oi-Pr)4 to give 1,5-dicarbonyl compounds in good yields. The reactions of acetals derived from α,β-unsaturated ketones with silyl enol ethers in the coexistence of TiCl4 and Ti(Oi-Pr)4, followed by successive addition of 1,2-ethanedithiol, give the Michael products, δ-keto
Bismuth Trichloride as a New Efficient Catalyst in the Aldol Reaction and the Michael Reaction
作者:Makoto Wada、Eiji Takeichi、Takashi Matsumoto
DOI:10.1246/bcsj.64.990
日期:1991.3
In the presence of a catalytic amount of bismuth(III) trichloride (5 mol%), silyl enol ethers react with aldehydes at room temperature in dichloromethane to give the corresponding aldols in good yields. Silyl enol ethers also have been found to react with α,β-unsaturated ketones at room temperature in dichloromethane to afford the corresponding 1,5-dicarbonyl compounds, the Michael adducts in good
In the presence of a catalytic amount of trityl perchlorate, 1,5-dicarbonyl compounds, the Michael adducts, are obtained in high yields by the reaction of silyl enol ethers with α,β-unsaturated ketones. The intermediate adducts, the synthetically valuable silyl enol ethers, are also isolated in high yields.
Enantioenriched 8-oxabicyclo[3.2.1]octane-6-carboxaldehydes were obtained by Lewis acid mediated homoaldol reaction of the (1Z,3R)-3-(tributylstannyl)but-1-enyl carbamate [(R)-7] with 1,5-diketones, followed by boron trifluoride mediated intramolecular aldol-type cyclization.