Abnormal Fischer indolization and its related compounds. XXII. Fischer indolization of ethyl pyruvate 2-(2-chloro- and 2,6-dichlorophenyl)methylhydrazones.
作者:Hisashi ISHII、Yasuoki MURAKAMI、Tsutomu ISHIKAWA
DOI:10.1248/cpb.38.597
日期:——
The Fischer indolization of ethyl pyruvate 2-(2-chlorophenyl)methylhydrazone (17) with HCl/EtOH proceeded rapidly to give six 1-methylindoles, ethyl 7-chloro (19), 6-chloro (22), and unsubstituted (24)-1-methylindole-2-car-boxylates, and dichloro derivatives (21, 23, and 26), whereas no indolization had occurred with the correspinding NH-hydrazone, as described in a previous paper. This result shows that the abnormal Fischer indolization of 2-chloro-phenylhydrazones with HCl/EtOH occurred in an ortho-C6 fashion, in the same manner as that of the corresponding 2-methoxyphenylhydrazones (1 and 2).The Fischer indolization of ethyl pyruvate 2-(2, 6-dichlorophenyl)methylhydrazone (18) with HCl/EtOH did not occur at all, whereas the reaction with ZnCl2/AcOH gave a low yield of ethyl 5, 7-dichloro-3-methylindole-2-carboxylate (36), which was formed by migration of the N-methyl group during Fischer indolization.
乙酰丙酮的Fischer吲哚化反应中,2-(2-氯苯基)甲基肼酮(17)与HCl/乙醇反应迅速生成六种1-甲基吲哚,包括乙基7-氯(19)、6-氯(22)和未取代(24)-1-甲基吲哚-2-羧酸酯,以及二氯衍生物(21、23和26),而与相应的NH-肼酮之间并未发生吲哚化反应,如前一篇论文所述。该结果表明,2-氯苯基肼酮与HCl/乙醇发生了异常的Fischer吲哚化反应,呈现出ortho-C6的方式,与相应的2-甲氧基苯基肼酮(1和2)的反应方式相同。乙酰丙酮2-(2, 6-二氯苯基)甲基肼酮(18)与HCl/乙醇的Fischer吲哚化反应完全未发生,而与ZnCl2/醋酸反应则得到了少量的乙基5, 7-二氯-3-甲基吲哚-2-羧酸酯(36),这是通过在Fischer吲哚化反应中N-甲基基团的迁移形成的。