Facile Access to 1,4-Disubstituted Pyrrolo[1,2-a]pyrazines from α-Aminoacetonitriles
作者:Ananta Karmakar、Sridharan Ramalingam、Mushkin Basha、Gopi Kumar Indasi、Makonen Belema、Nicholas A. Meanwell、T. G. Murali Dhar、Richard Rampulla、Arvind Mathur、Anuradha Gupta、Arun Kumar Gupta
DOI:10.1055/s-0039-1690699
日期:2020.2
An efficient and practical synthetic protocol for the synthesis of 1,4-disubstituted pyrrolo[1,2-a]pyrazine derivatives is described that originates from α-substituted pyrroloacetonitriles which, in turn, are readily available from aryl and alkyl aldehydes. The α-pyrroloacetonitriles were subjected to a Friedel–Crafts acylation with methyl chlorooxoacetate followed by reduction of the nitrile group
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。