A Convenient Preparative Method of Nitrile Oxides by the Dehydration of Primary Nitro Compounds with Ethyl Chloroformate or Benzenesulfonyl Chloride in the Presence of Triethylamine
nitrile oxides (MeOCOC≡N→O, PhC≡N→O, and EtC≡N→O) were effectively generated in situ by dehydration of the corresponding primary nitro compounds (RCH2NO2) with PhSO2Cl or ClCOOEt in the presence of triethylamine. Various cycloadducts were prepared by the reaction of them with dipolarophiles. Some advantages of these methods are described in comparison with other known methods.
A thermal decomposition of dimethyl nitromalonate to bis(carbomethoxy)furoxan was observed at about 170 °C. In the presence of dipolarophiles, an intermediate, methyl carbonocyanidate N-oxide MeOCOC≡N→O, could be trapped as cycloadducts in good yields by the 1,3-dipolar cycloaddition. Treatment of dimethyl nitromalonate in mesitylene at the refluxing temperature resulted in a formation of methyl 2-(hydroxyimino)-2-(2,4,6-trimethylphenyl)acetate.
Manganese(IV) oxide (MnO2) was found to oxidize aldoximes to nitrileoxides. Nitrileoxides were trapped in situ with dipolarophiles to furnish 2-oxazolines. The best results were obtained with hydroximinoacetates as nitrileoxide precursors.
Stability of electron deficient activated nitronates under neutral and Lewis acid catalyzed conditions. Facile nitronate cycloaddition reactions to the magnesium alkoxides of allylic alcohols leading to isoxazolidines and isoxazolines
作者:Shuji Kanemasa、Shinsuke Kaga、Eiji Wada
DOI:10.1016/s0040-4039(98)01902-9
日期:1998.11
exceptionally high reactivity to the magnesium alkoxides of allylic alcohols. Isoxazolidines or isoxazolines are formed as cycloadducts, depending upon the substitution pattern of the allylic alcohols. When the latter C-monosubstituted nitronate is treated with a catalytic amount of borontrifluoride etherate, the corresponding nitrile oxide is smoothly generated through β-elimination of methanol.
New methods of preparation of nitrile oxides and the corresponding disubstituted furoxans by interaction of N2O4 with salts of substituted dinitromethanes
作者:N. N. Makhova、I. V. Ovchinnikov、V. G. Dubonos、Yu. A. Strelenko、L. I. Khmel'nitsky
DOI:10.1007/bf00699994
日期:1993.1
A newmethod of generation of nitrile oxides through interaction of N2O4 with salts of substituted dinitromethanes (1) has been worked out. It has been shown by1H,13C,14N NMR spectroscopy that this reaction proceeds via dinitronitrosomethyl intermediates (one of these has been isolated), and that the reaction is feasible only for substituents capable of conjugation with the nitrile oxide fragment.