The stable monocyclic λ4-thiabenzenes 6aâe, which are stabilized with electron-withdrawing substituents such as benzoyl, cyano and alkoxycarbonyl groups, are synthesized in high yields by proton abstraction from the corresponding thiopyranium salts 5aâe with triethylamine in ethanol. The ylidic properties of the λ4-thiabenzenes are established based on spectral and chemical evidence. Thermal decomposition of the λ4-thiabenzenes affords alkyl-rearranged products 7, 8, and 9, thienofuran derivatives 10 (from benzoyl-substituted λ4-thiabenzenes), and thiophene derivatives 11. A plausible mechanism for the formation of those products is also discussed.
稳定的单环λ4-噻
苯(6a–e),通过
苯甲酰、
氰基和醇基羧基等电子吸引取代基得到高产率合成。这是通过用
三乙胺在
乙醇中从相应的噻
吡啶盐(5a–e)中抽取质子实现的。λ4-噻
苯的卤化属性则是根据光谱和
化学证据确立的。λ4-噻
苯的热分解得到烷基重排产物7、8和9、
噻吩呋喃衍
生物10(来自
苯甲酰取代的λ4-噻
苯)和
噻吩衍
生物11。文中还讨论了这些产物形成的合理机制。