1,4-Diazabicyclo[2.2.2]octane (DABCO) as an Efficient Reagent for the Synthesis of Isoxazole Derivatives from Primary Nitro Compounds and Dipolarophiles: The Role of the Base
作者:Luca Cecchi、Francesco De Sarlo、Fabrizio Machetti
DOI:10.1002/ejoc.200600475
日期:2006.11
The dehydration of primary nitro compounds can be performed by bases in the presence of dipolarophiles. The reactivity of several tertiary amines or azaheteroaromatic compounds containing one or two basic centres is shown to be related to the ability of the protonated base to establish H-bonded ion pairs with the adduct that is formed from the nitronate and the dipolarophile in chloroform. Among the
初级硝基化合物的脱水可以在偶极试剂存在下通过碱进行。几种叔胺或含有一个或两个碱性中心的氮杂杂芳族化合物的反应性被证明与质子化碱与氯仿中硝基和亲偶极体形成的加合物建立 H 键离子对的能力有关。在检测的有机碱中,笼状叔二胺 1,4-二氮杂双环 [2.2.2] 辛烷 (DABCO) 的结果最好。该反应适用于活化的硝基化合物和苯基硝基甲烷,与其他方法相比,异恶唑啉衍生物的产率更高。然而,该反应与硝基烷烃不相容。所提出的反应机理是基于氢键离子对的坍塌。