Hogg 1 Sulphines

Although many stable sulphines are known, the parent compound, CH2SO, has not been isolated. It is generated cleanly by flash vacuum pyrolysis of 1,3-di-thietan 1-oxide above 300 °C, and of thietan 5-oxide or methanesulphinyl 

Dichlorosulphine is formed in good yield by the thermal decomposition of p-anisyl trichloromethanesulphenate in acetonitrile or chloroform. The reaction is very sensitive to solvent polarity, and, in non-polar solvents, rearrangement of the sulphenate to the sulphoxide occurs by a polar mechanism. Since the trichloromethanesulphenate anion is known to give dichlorosulphine, an intermediate ion-pair is postulated, i.e. 

A new type of sulphine, phenylcyanosulphine, PhC(CN)=S=0, has been reported to be produced in low yield from the reaction of benzonitrile with thionyl chloride in the presence of hydrogen chloride. It gradually decomposes on standing to give tm/jj-a -dicyanostilbene and sulphur dioxide. 

Rotational isomerism in 3,3 -disubstituted diphenylsulphines has been studied by n.m.r. The deshielding of the ortho-protons syn to the CSO system depends upon the rotational equilibrium and hence on the solvent polarity. In apolar solvents the rotamer populations were approximately equal, or the rotamer with the lower dipole moment was slightly favoured. The more polar rotamer [e,g. (2)] was favoured in polar solvents. Rotational barriers about the aryl-sulphine bond have been determined, using a coalescence method, for 

Sulphines are formed by the oxidation of thiones with peroxy-acids, but they then react further, albeit much more slowly, to give the ketone, sulphur, and sulphur dioxide. This latter reaction is kinetically similar to many other oxidations with peroxy-acids, and the results are consistent with electrophilic attack of the peroxy-acid on the C=S double bond to give a cyclic sulphinate ester (4), which rapidly decomposes to give the ketone and sulphur monoxide. In contrast, oxidation of thiobenzanilide 5-oxide with m-chloroperoxybenzoic acid gives products derived from the sulphene PhC(NHPh)=SOa. Further examples of the reaction between diarylsulphines and aryldiazomethanes to give epi-sulphoxides have been reported.  

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