Neuartige Tricyclen aus Bis(arylthio)bicyclo[3.3.0]octadienen und Trimethylsilylcyanid in Gegenwart von Titan(IV)‐chlorid und Methanol

Abstract

Novel Tricyclic Products from Bis(arylthio)bicyclo[3.3.O]octadienes and Trimethylsilyl Cyanide in the Presence of Titanium Tetrachloride and Methanol[''A four-step sequence converting ketones into a$-unsaturated nitriles is put to test with the ketones 7 and 13. The tetramethylcyclohexanone 7 reacts with thiophenol or 4-chlorothiophenol in the presence of titanium tetrachloride and triethylamine to afford the phenyl vinyl sulphides 8. Treatment of 8 with a reagent, obtained from titanium tetrachloride and methanol, subsequent with trimethylsilyl cyanide produces the a-phenylthionitriles 9 in moderate yields. Oxidation of 9a with 3-chloroperbenzoic acid yields the a-phenylsulphinylnitrile 12 which decomposes at temperatures as low as 100°C to furnish a quantitative yield of the unsaturated nitrile 11. -When the mixture of bifunctional vinyl sulphides C2-, Cs-14a is allowed to react at -30°C with titanium tetrachloride/ methanol and, subsequently, with trimethylsilyl cyanide, a mixture of the bicyclic a-(pheny1thio)nitriles exo-15 and 16 and of the tricyclic products 17 and 18 is obtained. This mixture is separated by chromatography. At 20-25"C, the otherwise identical procedure furnishes an isomer of 17, viz. the tricyclic piperidine 21 a which is derived from a novel heterocyclic system. The gross structures are based on spectroscopic evidence. The configurations of 16,17, and 21 b, and the structure of 18 as well, are established by X-ray diffraction analyses. The mechanisms of the unexpected cyclization reactions leading to the tricyclic products 17, 18, and 21 are discussed.