Fischer indolization and its related compounds. XXIII. Fischer indolization of ethyl pyruvate 2-(2,6-dimethoxyphenyl)phenylhydrazone.
作者:Hisashi ISHII、Takao SUGIURA(nee HAGIWARA)、Yohko AKIYAMA(nee KONDO)、Yoshie ICHIKAWA、Toshiko WATANABE、Yasuoki MURAKAMI
DOI:10.1248/cpb.38.2118
日期:——
In order to clarify the mechanism of the abnormal Fischer indolization of 2-methoxyphenylhydrazones the Fischer indolization of ethly pyruvate 2-(2, 6-dimethoxyphenyl)phenylhydrazone (6) was undertaken using ethanolic hydrogen chloride and zinc chloride as an acid catalyst. The cyclization was found to take place predominantly on the 2, 6-dimethoxyphenyl nucleus to give the corresponding indoles, although the yields of indoles formed were low. Some non-indolic by-products were also produced which might give information about the mechanism of Fischer indolization. In particular, the formation of 3, 5-dimethoxy-4-anilinobenzaldehyde (15) suggests that the first cyclization step in Fischer indolization could take place at the para position of phenylhydrazone as a side reaction.
为了澄清2-甲氧基苯腈的异常费希尔吲哚化反应的机制,研究了乙基丙酮2-(2, 6-二甲氧基苯基)苯腈(6)的费希尔吲哚化反应,使用了氯化氢乙醇溶液和氯化锌作为酸催化剂。结果发现,环化主要发生在2, 6-二甲氧基苯核上,生成相应的吲哚,尽管所形成的吲哚产率较低。此外,还产生了一些非吲哚的副产品,这可能提供有关费希尔吲哚化机制的信息。特别是,3, 5-二甲氧基-4-苯胺醛(15)的形成提示,费希尔吲哚化反应的第一个环化步骤可能作为副反应发生在苯腈的对位。