(1E,3E)-4-Amino-3-cyano-4-methoxy-1-phenyl-2-azabutadiene (2) reacts with 2-methoxypropene in refluxing methylbenzene in the presence of catalytic pyridinium p-toluenesulfonate (PPTS) to give 2-cyano-5,5-dimethyl-3-methoxy-6-phenyl-4,5-dihydro-1,4-diazabenzene (5). Similarly, 2-aza-1,3-butadiene 2 reacts with triethyl orthoformate and triethyl orthobenzoate to give 3-cyano-2-methoxy-5-phenyl-1,4-diazabenzene (6) and 2-cyano-3-methoxy-5,6-diphenyl-1,4-diazabenzene (7), respectively. The PPTS-catalyzed reaction of 2 with triethyl orthoacetate gives 2-cyano-3-methoxy-5-methyl-6-phenyl-1,4-diazabenzene (8) and 2-cyano-5-ethoxy-3-methoxy-5-methyl-6-phenyl-4,5-dihydro-1,4-diazabenzene (9). Phenylmethanal and (2-thienyl)methanal react with 2-aza-1,3-butadiene 2 to give 5-methoxy-2,3-diphenyl-1,4-diazabenzene (17) and 5-methoxy-2-phenyl-3-(2-thienyl)-1,4-diazabenzene (18), respectively. Diazatrienes (enediimines) are proposed as the intermediates undergoing six pi-electron electrocyclizations to 1,4-diazabenzenes (dihydropyrazines, pyrazines, and pyrazinecarbonitriles).
(1E,3E)-4-
氨基-3-
氰基-4-甲氧基-1-苯基-2-亚基
丁二烯(2) 与
2-甲氧基丙烯在回流
甲苯中,在催化量的
吡啶N-对
甲苯磺酰胺(P
PTS)存在下反应,生成2-
氰基-5,5-二甲基-3-甲氧基-6-苯基-5,6-二氢-1,4-二氮杂苯(5)。Similar
环己烷条件下,2-氮杂-
1,3-丁二烯(2)分别与三乙基正边形酸酯和三乙基正
苯甲酸酯反应,生成3-
氰基-2-甲氧基-5-苯基-1,4-二氮杂苯(6)和2-
氰基-3-甲氧基-5,6
-二苯基-1,4-二氮杂苯(7)。P
PTS催化下,2与三乙基正
乙酸酯反应,生成2-
氰基-3-甲氧基-5-甲基-6-苯基-1,4-二氮杂苯(8),以及2-
氰基-5-乙氧基-3-甲氧基-5-甲基-6-苯基-6,7-二氢-1,4-二氮杂苯(9)。
苯甲醛和(2-
噻吩基)
甲醛与2-氮杂-
1,3-丁二烯(2)反应,生成5-甲氧基-2,3
-二苯基-1,4-二氮杂苯(17)和5-甲氧基-2-苯基-3-(2-
噻吩基)-1,4-二氮杂苯(18)。二氮杂
三烯(enediimines)被提出作为中间体,经过6π电子的电环化反应生成1,4-二氮杂苯(二氢
吡嗪、
吡嗪和
吡嗪腈)。