Synthesis and thermal Reactions of Cyano-Stabilized Cyclic Sulfur Ylides, 2-Alkyl-1-cyano-3,4-dihydro-1H-2-thionianaphthalen-1-ides

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1-Cyanoisothiochromans 4 were synthesized by the intramolecular Pummerer reaction of cyanomethyl phenethyl sulfoxides 3 with trifluoroacetic anhydride. Alkylation of the isothiochromans 4 afforded isothiochromanium salts 5 which consist of cis- and trans-isomers. 1-Cyano-2-methyl-3,4-dihydro-1H-2-thionianaphthalen-1-ides 6 were prepared by deprotonation of 5 with triethylamine or sodium hydride. Thermal reaction of the ylide 6a in benzene or N, N-dimethylform-amide gave the 1,2-rearranged product 7 accompanied with the dimers 8,whereas the reaction in acetonitrile gave the dimers E-8 (8-I) (31.6%) and Z-8 (8-II) (22.6%) as the major products. The geometrical structures of 8 were determined by infrared (IR) and Raman spectroscopy. The dimers 8 were formed at room temperature by treatment with tetracyanoethylene or 7,7,8,8-tetracyano-quinodimethane. Unexpected products, 1-benzylated isothiochromans 10,were obtained upon heating 6a in toluene and its derivatives. A reaction mechanism involving the benzyl radicals was postulated for this novel solvent-uptake reaction.
社団法人日本薬学会の論文
1988-05-25