The reaction of 2-hydroxybenzaldehydes with 3-oxobutanoic esters and excess ammonia in acetic acid at room temperature yields dialkyl 2-(2-hydroxyphenyl)-4,6-dimethyl-1,2-dihydropyridine-3,5-dicarboxylates and their 2-(3,5-dialkoxycarbonyl-4,6-dimethyl-1,2,3-trihydropyridinium-2-yl)-phenoxide zwitterions. Mild oxidation of these compounds is accompanied by lactonisation, with formation of alkyl 2,4-dimethyl-5-oxo-5H-[1]benzopyrano[4,3-b]pyridine-3-carboxylates, which had previously been incorrectly formulated. Reaction of other o-substituted benzaldehydes with alkyl 3-aminocrotonates in acetic acid at room temperature also yields dialkyl 2-aryl-4,6-dimethyl-1,2-dihydropyridine-3, 5-dicarboxylates, as well as the normal 1,4-dihydropyridine Hantzsch esters.
2-羟基
苯甲醛与
3-氧代丁酸酯和过量
氨在室温下的
醋酸中反应,生成二烷基2-(2-羟基苯基)-4,6-二甲基-1,2-
二氢吡啶-
3,5-二羧酸酯及其2-(3,5-二烷氧羧基-4,6-二甲基-1,2,3-三氢
吡啶离子-2-基)-苯氧负离子。对这些化合物的温和氧化伴随有内酯化,形成之前被错误表述的烷基2,4-二甲基-5-氧代-5H-[1]苯并
吡喃[4,3-b]
吡啶-3-
羧酸酯。其他o-取代
苯甲醛与烷基3-
氨基克罗通酸酯在室温下的
醋酸中反应同样生成二烷基2-芳基-4,6-二甲基-1,2-
二氢吡啶-
3,5-二羧酸酯,以及常见的1,4-
二氢吡啶汉兹施酯。