S-Alkoxy-S,S-diarylthiazynes were prepared by two methods: the alkaline hydrolysis of S,S-diaryl-N-halosulfilimines in aqueous alcohols and the reaction of S,S-diaryl-S-fluorothiazynes with sodium alkoxides. The structure of S,S-diphenyl-S-propoxythiazyne was determined by an X-ray crystallographic analysis, which showed a short SN bond length of 1.441(3) Å. The thermolysis of S-alkoxythiazynes gave elimination products, which were identified as the corresponding carbonyl compounds and N-unsubstituted S,S-diarylsulfilimines. Kinetic experiments for the thermolysis of the S-alkoxy-S,S-diarylthiazynes were carried out. The first-order kinetic behavior, a large kinetic isotope effect (kH/kD = 6.1) using S,S-diphenyl-S-[1,1-2H2]propoxythiazyne, a negative activation entropy (ΔS‡ = −30 J K−1mol−1), and a negative Hammett ρ-value (ρ = −0.35) on the phenyl group were obtained, suggesting that the reaction proceeds via a concerted five-membered cyclic transition state. A deviation from the ideal concerted transition state is discussed in comparison with that for sulfoxides.
Reaction of S,S-diaryl-S-fluorothiazynes6) with cyclic secondary amines gave novel thiazynes, the corresponding S-aminothiazynes in good yields. Spectroscopic studies, measurement of pKa values, pyrolysis and alkylation reactions of the aminothiazynes were carried out.
Several diaryl(fluoro)-λ6-sulfanenitriles 3 were synthesized by the reaction of S,S-diarylsulfimides 1 with Selectfluor™. This reaction also allows the first preparation of heterocyclic fluoro-λ6-sulfanenitrile, 5-fluoro-10,10-dioxo-5,10-dihydro-5λ6,10λ6-thianthren-5-nitrile (5) and its molecular structure was determined by X-ray crystallographic analysis.