Thermal rearrangements of cyclic amine ylides. II. Ring-expansion of 4-and 6-vinyl-1,2,5,6-tetrahydropyridine and 2-vinylpiperidine N-imides.
作者:TAKASHI TSUCHIYA、HARUKI SASHIDA
DOI:10.1248/cpb.29.1887
日期:——
The thermolysis of the 4-vinyl-1, 2, 5, 6-tetrahydropyridine N-imide (13a) resulted in both [1, 2-]- and [2, 3]-sigmatropic rearrangements to give the tetrahydro-1, 2-diazepine (18) and the 3, 3-divinyltetrahydropyrazole (19), respectively ; this reaction mechanism was confirmed by a deuterium-labelling experiment. In contrast, the thermolysis of both 6-vinyl-1, 2, 5, 6-tetrahydropyridine N-imide (13b) and 2-vinylpiperidine N-imide (17) resulted in only [2, 3] rearrangement with the vinyl group to give nine-membered ring products, the tetrahydro- (21) and the hexahydro-1, 2-diazonine (25), respectively. The starting vinyltetrahydropyridine N-imides (13a, b) were prepared from the corresponding vinylpyridines (10a, b), and 2-vinylpiperidine N-imide (17) was prepared from 1-ethoxycarbonyl-2-vinylpiperidine (14).
4-vinyl-1, 2, 5, 6-四氢
吡啶 N-
亚胺(13a)的热分解导致[1, 2]-和[2, 3]-异构重排,分别生成四氢-1, 2-二氮杂卓(18)和 3, 3-二
乙烯基四氢
吡唑(19);
氘标记实验证实了这一反应机理。相反,6-
乙烯基-1,2,5,6-四氢
吡啶 N-
酰亚胺(13b)和 2-
乙烯基哌啶 N-
酰亚胺(17)在热分解过程中只与
乙烯基发生[2,3]重排反应,生成九元环产物,分别是四氢-(21)和六氢-1,2-二氮杂
吲哚(25)。起始
乙烯基四氢
吡啶 N-
亚胺(13a、b)由相应的
乙烯基吡啶(10a、b)制备,2-
乙烯基哌啶 N-
亚胺(17)由 1-乙氧羰基-2-
乙烯基哌啶(14)制备。