thiazole ring opening. Diethyl azodicarboxylate also gave 2,3-dihydro-1H-1,2,4-triazole derivatives in moderate yields. High pressure improved the yields a little. On the other hand, the reaction of diethyl oxomalonate in the presence of tin tetrachloride with 4-unsubstituted thiazoles did not give an adduct of similar type but gave diethyl 2-hydroxy-2-(4-thiazolyl)malonate through the usual electrophilic
5-烷氧基
噻唑与等摩尔量的 4-苯基-3H-
1,2,4-三唑-3,5(4H)-二酮 (
PTAD) 在
乙腈溶液中在室温下反应得到相应的 O-烷基 6, 7-dihydro-5,7-dioxo-6-phenyl-1H,5H-[1,2,4]triazolo[1,2-a] [1,2,4]triazole-1-carbothioate,收率很高。假设反应是通过向
噻唑逐步添加
PTAD 并伴随
噻唑开环来进行的。偶氮二
羧酸二
乙酯也以中等产率得到2,3-二氢-
1H-1,2,4-三唑衍
生物。高压稍微提高了产量。另一方面,在
四氯化锡存在下,氧代
丙二酸二乙酯与 4-未取代的
噻唑的反应没有得到类似类型的加合物,而是通过通常的亲电取代反应得到 2-羟基-2-(4-
噻唑基)
丙二酸二乙酯C-4 位的
噻唑。