Preparation of New Nitrogen-Bridged Heterocycles. XXXI. Cyclization Aptitudes of 2-Acylmethylthio-3-cyanoindolizines Having a Cyano or an Ester Group at the 1-Position.
作者:Akikazu KAKEHI、Suketaka ITO、Tsuneo FUJII、Tatsuya UEDA、Tomohiro HIRATA
DOI:10.1248/cpb.40.2313
日期:——
Some 2-acylmethylthio-3-cyanoindolizine derivatives having a cyano or an ethoxycarbonyl group at the 1-position were prepared and their intramolecular cyclization reactions were examined. The alkaline treatment of these polyfunctionalized indolizines in refluxing ethanol gave only 3-aminothieno[2, 3-b]indolizine derivatives in moderate to good yields regardless of the kind of 1-substituent, and the other possible alternative, a thieno[3, 2-α]indolizine derivative, could not be obtained at all. The higher reactivity of the 3-cyano group over 1-cyano and 1-ethoxycarbonyl groups coincided well with the results expected from molecular orbital calculations for the model compounds. From our present and previous results, the order (3-CN>1-CN>3-ester>1-ester) of the reactivities of electron-withdrawing groups at the 1- and 3-positions on the indolizing ring was finally estblished.
研究人员制备了一些 2-酰基甲硫基-3-氰基吲嗪衍生物,这些衍生物的 1-位上有一个氰基或乙氧基羰基,并对它们的分子内环化反应进行了研究。在回流乙醇中对这些多官能团化的吲嗪进行碱性处理后,无论 1-取代基的种类如何,都只能得到中等至良好产率的 3-氨基噻吩并[2, 3-b]吲嗪衍生物,而另一种可能的选择,即噻吩并[3, 2-α]吲嗪衍生物,则根本无法得到。与 1-氰基和 1-乙氧羰基相比,3-氰基的反应活性更高,这与模型化合物分子轨道计算的预期结果非常吻合。根据我们目前和以前的研究结果,最终确定了吲哚化环上 1 位和 3 位上的取电子基团的反应活性顺序(3-CN>1-CN>3-酯>1-酯)。