An efficient carbanionic synthesis of the phosphonic dicarbonylated compounds 2 was achieved and used as key intermediates in the synthesis of the phosphonic furans 4 by acid-induced Paal-Knorr cyclization reaction.
A general stereoselective method for the synthesis of cyclopropanecarboxylates. A new version of the homologous Horner–Wadsworth–Emmons reaction
作者:Henryk Krawczyk、Katarzyna Wąsek、Jacek Kędzia、Jakub Wojciechowski、Wojciech M. Wolf
DOI:10.1039/b712145h
日期:——
The synthesis of α-, β- and γ-substituted α-phosphono-γ-lactones was accomplished using different ring closure and ring homologation strategies. It was found that the lactones could be selectively transformed into the corresponding ethyl cyclopropanecarboxylates by treatment with sodium ethoxide in boiling THF. The reported reaction provides an attractive alternative to the classical homologous HornerâWadsworthâEmmons approach to the construction of cyclopropanes with electron-withdrawing functionalities.
Two one-pot procedures starting from diethyl 3,3-diethoxybutyl-phosphanate and aldehydes are proposed for the stereoselective synthesis of the title compounds. In the first one, the use of a Peterson reagent generated in situ, leads to a high (Z)-stereoselective olefination process. In the second, a base-induced 1,2-elimination reaction of a phosphate derivative controls the (E)-stereoselective formation of the double bond.