Synthesis and thermal transformation of stable monocyclic λ4-thiabenzenes

Article abstract of DOI:10.1039/b102806p

The stable monocyclic λ⁴-thiabenzenes 6a-e, 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 5a-e 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.