Studies on diazepines. XVII. Synthesis of monocyclic 1,3-diazepines. (2). Substituent effects on the thermal ring-conversion of 1,2-diazepines into 1,3-diazepines.
作者:JYOJI KURITA、HIROKAZU KOJIMA、MICHIKO ENKAKU、TAKASHI TSUCHIYA
DOI:10.1248/cpb.29.3696
日期:——
The thermolysis of 1, 2-diazepines (7a-f and 11) having an electron-donating substituent in the 4- or 6-position resulted in the formation of the 1, 3-diazepines (9 and 12) and 2-aminopyridines (10), whereas 1, 2-diazepines (7g-k) having an electron-withdrawing substituent in the same position gave only 2-aminopyridines (10) and no 1, 3-diazepines. However, the thermolysis of 3-, 5-, or 7-substituted 1, 2-diazepines with either an electron-donating or-withdrawing substituent did not give 1, 3-diazepines. Heating of the bicyclic compounds (8) also gave the corresponding 1, 3-diazepines. Based on these results, we concluded that the presence of an electron-donating substituent is essential for this ring-conversion of 1, 2-diazepines into 1, 3-diazepines. These substituent effects and the reaction mechanism are discussed.
热分解在 4 位或 6 位上具有一个电子奉献取代基的 1,2-二氮杂卓(7a-f 和 11),可生成 1,3-二氮杂卓(9 和 12)和 2-氨基吡啶(10),而在同一位置上具有一个电子抽取取代基的 1,2-二氮杂卓(7g-k)则只生成 2-氨基吡啶(10),而不生成 1,3-二氮杂卓。然而,热分解 3-、5-或 7-取代的 1,2-二氮杂卓,无论其取代基是给电子还是抽电子,都不能得到 1,3-二氮杂卓。加热双环化合物 (8) 也能得到相应的 1,3-二氮杂卓。根据这些结果,我们得出结论:1, 2-二氮杂卓环状转化为 1, 3-二氮杂卓的过程中,必须存在一个电子奉献取代基。本文讨论了这些取代基的作用和反应机理。