A series of the title ylides was prepared by reaction of fused thiophene and selenophene derivatives with di-tert-butyl diazomalonate. Their thermal stability depended highly on their structure. While the terminal thiophenium- and selenophenium-ylides smoothly rearranged to the corresponding thiopyran and selenopyran derivatives, the internal thiophene ylides showed remarkable stability. The latter also exhibited hindered rotation around the S–C ylide bond and a high rotational barrier could be established in an NMR study.
一系列标题为叶立德的化合物通过将融合的
噻吩和
硒吩衍
生物与双叔丁基重氮
丙二酸酯反应制备而成。它们的热稳定性高度依赖于它们的结构。虽然末端
噻吩和
硒吩叶立德平稳地重排成相应的
噻吩并
硒吩
吡喃衍
生物,但内部
噻吩叶立德表现出显著的稳定性。后者还表现出
硫-碳叶立键周围的受阻旋转,并且在核磁共振研究中可以建立高旋转能垒。