Reaction between proline and γ-oxo α,β-unsaturated esters: new access to polysubstituted pyrrolizidines
作者:Pedro de March、Laia Elias、Marta Figueredo、Josep Font
DOI:10.1016/s0040-4020(02)00145-x
日期:2002.3
The reactions between proline and several gamma-oxo alpha, beta-unsaturated esters have been studied in detail. The products isolated are in all cases derived from one molecule of proline and two molecules of the ester. The new polysubstituted pyrrolizidines result from the cycloaddition of an azomethine ylide to a second molecule of the unsaturated ester in a stereoselective manner. (C) 2002 Elsevier Science Ltd. All rights reserved.
Acetals of γ-oxo-α,β-unsaturated esters in nitrone cycloadditions. Regio- and stereochemical implications
作者:Ramon Alibés、Félix Busquè、Pedro de March、Marta Figueredo、Josep Font、Maria Esmeralda Gambino、Brian A. Keay
DOI:10.1016/s0957-4166(01)00294-4
日期:2001.7
Several acetals of gamma -oxo-alpha,beta -unsaturated esters have been prepared, mainly from enantiopure C-2-symmetric diols, and their 1,3-dipolar cycloaddition to 2,3,4,5-tetrahydropyridine 1-oxide has been studied. All the reactions showed complete regio selectivity and a high preference for the endo approach of the reactants in the transition state. The enantiopure acetals derived from (cis, cis) -spiro [4.4]nonane- 1, 6-diol gave the highest diastereofacial selectivity. (C) 2001 Elsevier Science Ltd. All rights reserved.
On the regioselectivity in nitrone cycloadditions to γ-oxo α,β-unsaturated esters
作者:Ramón Alibés、Félix Busqué、Pedro de March、Marta Figueredo、Josep Font、Teodor Parella
DOI:10.1016/s0040-4020(98)00628-0
日期:1998.9
The 1,3-dipolar cycloadditions of the cyclic nitrones 1 and 2 to several γ-oxo α,β-unsaturatedesters, 5–10, are reported. A strong predominance of the regioisomers with the oxygen atom of the dipole attached to the β-ester position is observed. This high regioselectivity is attributed to steric factors. The reduction of the carbonyl group of some of the major cycloadducts is a good yielding procedure