Synthesis, Structure, and Thermolysis Mechanism of S-Alkoxythiazynes

Abstract

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.

Application of alkoxy‐λ6‐sulfanenitriles as strong alkylating reagents

“…We reported previously that alkoxy-6 -sulfanenitriles undergo facile Ei reaction in refluxing benzene to afford the corresponding elimination products and N-unsubstituted diphenylsulfilimine [5]. Ei reactions of sulfoxides and sulfilimines in protic solvents are known to undergo rate retardation [9,10], which is attributable to the result of no Ei reaction of 1e in phenol and p-cresol.…”

“…Elemental analyses were performed on a Yanaco MT-5 CHN CORDER. Fluoro-and alkoxy-6 -sulfanenitriles were prepared according to the methods reported in our previous papers [5,6].…”

“…In recent years, we have prepared a series of organic 6 -sulfanenitriles [4,5], and have reported the X-ray structural analysis of some 6 -sulfanenitriles [4c,4d,5]. In our previous paper [5], it was reported that alkoxy- 6 -sulfanenitriles [5] exceptionally undergo a facile Ei reaction, although 6 -sulfanenitriles are tetracoordinated hexavalent sulfur compounds like sulfones and sulfoximides.…”

“…In our previous paper [5], it was reported that alkoxy- 6 -sulfanenitriles [5] exceptionally undergo a facile Ei reaction, although 6 -sulfanenitriles are tetracoordinated hexavalent sulfur compounds like sulfones and sulfoximides. Furthermore, during the synthesis and the assignment of the structure of these alkoxy- 6 -sulfanenitriles [5,6], it was found that they undergo acid-catalyzed hydrolysis readily, even under slightly alkaline conditions, to yield the corresponding sulfoximide [2] and alcohols.…”

“…In our previous paper [5], it was reported that alkoxy- 6 -sulfanenitriles [5] exceptionally undergo a facile Ei reaction, although 6 -sulfanenitriles are tetracoordinated hexavalent sulfur compounds like sulfones and sulfoximides. Furthermore, during the synthesis and the assignment of the structure of these alkoxy- 6 -sulfanenitriles [5,6], it was found that they undergo acid-catalyzed hydrolysis readily, even under slightly alkaline conditions, to yield the corresponding sulfoximide [2] and alcohols. Moreover, we reported that methoxydiphenyl- 6 -sulfanenitrile reacts with thiols to give methyl sulfides and diphenyl sulfoximide, and clarified the mechanism that involves an initial equilibrated protonation of the 6 -sulfanenitrile by thiols followed by nucleophilic attack of the thiolate anions on the methyl group in the rate-determining step [7].…”