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Cowell, Geoffrey (1963) The preparation and properties of some aryl pyrazolyl sulphides. Doctoral thesis, Northern Polytechnic.
Some aryl pyrazolyl sulphides have been prepared by the action of hydrazines on ß-diketones and the structure of these compounds confirmed by the direct action of o-nitrobenzenesulphenyl chloride on the appropriate pyrazole. It was shown that the 4-position of pyrazoles is directly attacked by o-nitrobenzenesulphenyl chloride in the absence of a catalyst, which is a method not used before. Furthermore, the novel technique of melting together of the substrate and the reagent often led to better yields. o-Nitrobenzenesulphenyl chloride was also shown to attack 1-unsubstituted pyrazoles at the 1-position only, at the 4- position only, or at both 1- and 4-positions according to the conditions used. The pyrazolyl-1 sulphides have been shown to undergo hydrolysis with aqueous acetic acid to give the parent pyrazole.
1-(2,4-Dinitrophenyl)-pyrazolyl-4 sulphides were cleaved by methanolic sodium methoxide to give the pyrazolyl-4 sulphide and 2,4-dinitrophenol. 1-(2,4-Dinitrophenyl)-pyrazoles give the pyrazole and 2,4-Dinitroanisole.
The oxidation of pyrazolyl-4 sulphides by hydrogen peroxide gave good yields of sulphones in all cases. Where, however, the pyrazole was substituted, in both the 3- and 5-positions with phenyl groups, no sulphoxide was obtained.
The N-sulphide of acetanilide was prepared and previous work on this problem reinvestigated. The hydrolysis of this sulphide, the pyrazolyl-1 sulphides, and o-nitrobenzenesulphenyl chloride, in aqueous acetic acid, were investigated. The mechanism of these hydrolyses have been discussed.
The reaction of o-nitrobenzenesulphenyl chloride with a number of aromatic compounds was investigated. Reaction was shown to occur in the absence of any Friedel-Crafts catalyst with ‘active’ aromatics.
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