1,3-Dipolar cycloaddition reactions of nitrones with alkyl vinyl ethers catalyzed by chiral oxazaborolidines
作者:Jean-Paul G. Seerden、Mike M.M. Boeren、Hans W. Scheeren
DOI:10.1016/s0040-4020(97)00757-6
日期:1997.8
The 1,3-dipolar cycloaddition reactions of various Z- and E-nitrones with ethyl vinylether and 2,3-dihydrofuran are catalyzed by 20 mol% of chiral oxazaborolidines at room temperature. The effect of high pressure on these reactions is discussed.
The 1,3-dipolar cycloadditions of enolethers as electron-rich olefins with C-phenyl-N-alkyl nitrones proceeded smoothly in the presence of easy handling palladium(II) catalysts under mild conditions to give isoxazolidines in good yield.
Reactions at high pressures. [3+2] Dipolar cycloaddition of nitrones with vinyl ethers
作者:Carl Michael Dicken、Philip DeShong
DOI:10.1021/jo00132a014
日期:1982.5
Determination of configuration and conformation of isoxazolidines by nuclear Overhauser effect difference spectroscopy
作者:Philip DeShong、C. Michael Dicken、Ronald R. Staib、Alan J. Freyer、Steven M. Weinreb
DOI:10.1021/jo00144a002
日期:1982.11
Synthese von 4-Alkoxy- und 3-nitrosubstituierten Isoxazolidinen durch katalysierte 1,3-dipolare Cycloadditionsreaktionen von Nitronen mit Vinylethern und Nitroolefinen
作者:Michael Meske
DOI:10.1002/prac.19973390175
日期:——
1,3-Dipolar cycloadditions of the C-phenyl-N-alkylnitrones 1,3 and the C,N-diphenylnitrone (2) with vinyl ethers 5,6 are strongly catalyzed by chiral oxazaborolidines derived from N-arylsulfonyl substituted L-alpha-amino acids valine and tert-butyl leucine and BH3 . THF complex at -22 degrees C to room temperature to give predominantly the 3,5-trans-substituted 5-alkoxy-isoxazolidines 8b - 12b, but with moderate enantioselectivity. Thermal cycloaddition afforded predominantly the 3,5-cis-substituted 5-alkoxy-isoxazolidines 8a - 12a. The cycloaddition of (E)-1-ethyl-2-nitroethene (7) afforded a mixture of cis- and trans-substituted 4-nitro-isoxazolidines 13. The ratio depends on reaction temperature and catalyst. Mild ring cleavage after quarternization of 5-ethoxy-2-methyl-isoxazolidines (8) yields the corresponding beta-amino-esters 27, 28.