描述了一种用于合成1,4-二取代的吡咯并[1,2- a ]吡嗪衍生物的有效且实用的合成方案,其源自α-取代的吡咯并乙腈,而α-取代的吡咯并乙腈可容易地从芳基和烷基醛获得。将α-吡咯乙腈与氯氧乙酸甲酯进行Friedel-Crafts酰化反应,然后在Pd催化的氢化条件下还原腈基,最后用DDQ进行芳构化,得到所需的吡咯并[1,2- a]吡嗪衍生物。该方法被普遍化并成功地应用于各种芳基,杂芳基和烷基底物。所开发的方案可直接且方便地以中等至良好的总收率(51–68%)访问1,4-二取代的环系统,而无需纯化中间体。还证明了通过逐步卤化(溴化,碘化)和硝化的进一步官能化。另外,通过操作成杂环系统证明了酯官能化的潜力,例如通过转化为苯并恶唑衍生物。
One-Pot Synthesis of Polysubstituted Indolizines by an Addition/Cycloaromatization Sequence
作者:Murat Kucukdisli、Till Opatz
DOI:10.1021/jo400992n
日期:2013.7.5
Indolizines carrying various substituents in positions 5-8 were obtained from readily available 2-(1H-pyrrol-1-yl)nitriles and alpha,beta-unsaturated ketones or aldehydes in a one-pot procedure. Michael addition of the deprotonatecl aminonitriles to the acceptors followed by acid catalyzed electrophilic cyclization produces 5,6-dihydroindolizine-5-carbonitriles. From these stable intermediates, substituted indolizines were obtained via base induced dehydrocyanation.