Fischer Indolization of Ethyl Pyruvate 2-(2-(Trifluoromethyl)phenyl)-phenylhydrazone and New Insight into the Mechanism of the Goldberg Reaction. (Fischer Indolization and Its Related Compounds. XXVI)
作者:Yasuoki MURAKAMI、Toshiko WATANABE、Takao HAGIWARA、Yohko AKIYAMA(nee KONDO)、Hisashi ISHII
DOI:10.1248/cpb.43.1281
日期:——
The Fischer indolization of ethyl pyruvate 2-[2-(trifluoromethyl)phenyl]phenylhydrazone (5) gave two indolic products, ethyl 7-(trifluoromethyl)-1-phenylindole-2-carboxylate (12) as a minor product and ethyl 1-[2-(trifluoromethyl)phenyl]indole-2-carboxylate (13) as a major product. This result shows that the Fischer indolization occurred on the more electron-rich phenyl group. In the Goldberg reaction to prepare 13 from ethyl indole-2-carboxylate (15) and o- (21) or m-bromo-α, α, α-trifluotoluene (23), it was found that Goldberg reaction proceeds via a benzyne mechanism, at least in part, in a sterically crowded situation.
Fischer吲哚合成法对乙基丙二酸酯2-[2-(三氟甲基)苯基]苯肼(5)进行反应,得到两个吲哚产物,分别是少量产物乙基7-(三氟甲基)-1-苯基吲哚-2-羧酸酯(12)和主要产物乙基1-[2-(三氟甲基)苯基]吲哚-2-羧酸酯(13)。这一结果表明,Fischer吲哚合成发生在电子云密度更高的苯基上。在通过Goldberg反应由乙基吲哚-2-羧酸酯(15)和邻位(21)或间位溴-α, α, α-三氟甲苯(23)制备13的过程中发现,Goldberg反应至少在一定程度上通过苯炔机制进行,尤其是在空间位阻较大的情况下。