Reaction of ketene silyl acetals with allylic carbonates in the presence of palladium-phosphine catalyst in dioxane gives α-allyl esters in high yields. When the reaction is carried out with phosphine-free palladium catalyst in nitriles, α,β-unsaturated esters are obtained in good yields.
It was found that the reaction of O-silylated enolates of carboxylicesters and of lactones with aminomethyl ethers proceeds smoothly under a catalytic action of zinc chloride to afford the corresponding α-aminomethylated carboxylicesters or lactones, except only one case using O-silylated enolate of δ-valerolactone, in which the resultant α-aminomethyl-δ-valerolactone is somewhat unstable and undergoes
Etude de la reaction chlorocarbene-acetals de cetenes
作者:N. Slougui、G. Rousseau
DOI:10.1016/s0040-4020(01)96366-5
日期:1985.1
The reaction of chloro, chloromethyl and chlorophenyl carbenoids with ketene alkylsilylacetals has been studied. Excellent yields of cyclopropanation were observed and the unstable chlorocyclopropanone acetals formed were thermallyrearranged in high yield into α-substituted α,β-ethylenic esters. This new method for the synthesis of unsaturated esters appeared complementary of the known-ones.
New synthetic methods for α,β -unsaturated ketones, aldehydes, esters and lactones by the palladium-catalyzed reactions of silyl enol ethers, ketene silyl acetals, and enol acetates with allyl carbonates
Silyl enol ethers and ketenesilylacetals derived from ketones, aldehydes, esters and lactones are converted into α,β-unsaturated ketones, aldehydes, esters and lactones by treatment with allyl carbonates in high yields using the palladium—bis(diphenylphosphino)ethane (dppe) complex as catalyst. Phosphine-free palladium catalyst instead of the palladium—phosphine complex gives a higher selectivity
Unprecedented Reactivity Pattern of Chromium Fischer Carbene Complexes. Direct Application to One-Pot Synthesis of 4-Aryl-3,4-dihydrocoumarins on a Multigram Scale
作者:José Barluenga、Facundo Andina、Fernando Aznar
DOI:10.1021/ol060702e
日期:2006.6.1
[reaction: see text] Reaction of alkenyl carbene chromium(0) complexes and ketene acetals triggers the formation of 4-aryl-3,4-dihydrocoumarins. The reaction can be carried out as a simple one-pot protocol in air atmosphere. The huge interest of dihydrocoumarins has prompted us to optimize a multigram-scale process.