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。