behaviour to azlactones. However, the mechanism of their reaction with dimethylacetylenedicarboxylate or with ethyl vinyl ether differs fundamentally. In the thiazole series, the first step is the quaternization of the nitrogen atom. The mesoionic thiazole intermediate is then trapped by a second molecule of the dipolarophile.
4-羟基
噻唑和N-
嘧啶基4-
噻唑烷
酮类具有与a内酯相似的互变异构行为。然而,它们与二甲基
乙炔二
羧酸酯或与乙基
乙烯基醚反应的机理有根本不同。在
噻唑系列中,第一步是氮原子的季
铵化。然后,介电性
噻唑中间体被亲双性分子的第二分子捕获。