Preparation of new nitrogen-bridged heterocycles. XXII. A new approach to the syntheses of thienoindolizine derivatives.
作者:Akikazu KAKEHI、Suketaka ITO、Naoaki YAMADA、Kiminobu YAMAGUCHI
DOI:10.1248/cpb.38.1527
日期:——
Ethyl 2-[(2-substituted ethyl)thio]-3-indolizinecarboxylates (1a-f and 5a-f) were deprotected with potassium tert-butoxide in N, N-dimethylformamide and the resulting potassium 2-indolizinethiolates were alkylated with various alkylating agents such as chloroacetone (3a), phenacyl bromides (3b-d), and nitrobenzyl bromides (3e, f) to afford smoothly the corresponding S-functinoalized indolizine derivatives (4a-r and 6a-r) in considerable yields. On the other hand, the similar reactions of 3-acetyl-2-[(2-substituted ethyl)thio]indolizines (7a-f) provided 3-metylthieno[2, 3-b]indolizine derivatives (8a-o), formed via the further intramolecular cyclization of the initially generated S-alkylated indolizines under the reaction conditions employed here. The functionalized indolizines (4a-r and 6a-r) obtained above could also be transformed to the corresponding thieno[3, 2-α]-(10a-r, 14a-d, and 15a, b) and thieno[2, 3-b]indolizine derivatives (11a-h and 12a-d) under various alkaline conditions.
在 N,N-二甲基甲酰胺中用叔丁醇钾对 2-[(2-取代乙基)硫]-3-吲嗪甲酸乙酯(1a-f 和 5a-f)进行脱保护,并用各种烷基化剂如氯丙酮(3a)对生成的 2-吲嗪硫醇钾进行烷基化、苯甲酰基溴化物(3b-d)和硝基苄基溴化物(3e,f)进行烷基化,可顺利得到相应的 S-羽氨化吲哚利嗪衍生物(4a-r 和 6a-r),产率相当高。另一方面,3-乙酰基-2-[(2-取代乙基)硫代]吲嗪(7a-f)的类似反应提供了 3-甲基噻吩并[2, 3-b]吲嗪衍生物(8a-o),这些衍生物是最初生成的 S-烷基化吲嗪在此处采用的反应条件下进一步分子内环化形成的。上述官能化的吲嗪类化合物(4a-r 和 6a-r)还可以在各种碱性条件下转化为相应的噻吩并[3,2-α]-(10a-r、14a-d 和 15a,b)和噻吩并[2,3-b]吲嗪衍生物(11a-h 和 12a-d)。