Conjugate Addition versus Cycloaddition/Condensation of Nitro Compounds in Water: Selectivity, Acid-Base Catalysis, and Induction Period
作者:Luca Guideri、Francesco De Sarlo、Fabrizio Machetti
DOI:10.1002/chem.201202698
日期:2013.1.7
react in water as in chloroform with electron‐deficient dipolarophiles to give condensation or conjugate addition products under basecatalysis. In general, high selectivity towards condensation is observed in water, with shorter induction periods than in chloroform. In water, condensations slowly occur even without base; kinetic profiles evidence the catalytic effect of the base, which should be related
Aromatic and aliphatic nitrile oxides are generated by the oxidation of α-hydroxyimino carboxylic acid with ammoniumhexanitratocerate(IV). They react with olefinic and acetylenic dipolarophiles to give the corresponding cycloaddition products in good yield. The oxidation of α-oxo aldoximes also affords α-oxo carbonitrile oxides.
Several improvements in the cycloaddition of carboethoxyformonitrile oxide (CEFNO) with different alkenes are observed in the ionic liquids [bmim][BF4] and [bmim][PF6]. The possibility of obtaining good yields of the corresponding isoxazolines opens the way towards parallel collections of glutamic acid (Glu) analogues. (C) 2003 Elsevier Science Ltd. All rights reserved.
Ethyl 2-nitroacetoacetate as a new synthetic equivalent of ethoxycarbonylnitrile oxide
作者:V. P. Kislyi、A. L. Laikhter、B. I. Ugrak、V. V. Semenov
DOI:10.1007/bf00699144
日期:1994.1
It was shown that ethyl 2-nitroacetoacetate is a synthetic precursor of ethoxycarbonylnitrile oxide as well as of isoxazole- and isoxazoline-3-carboxylic acids and their esters. The elimination of acetic acid from ethyl 2-nitroacetoacetate occurs in a mixture of acetic acid and acetic anhydride in the presence of strong mineral acids, e.g., H2SO4, at room temperature and gives isoxazolines in yields of up to 85-91 %.