Chemistry of sulfines. Part III: Further investigations on the preparation

The preparation of sulfines by oxidation of thioketones is described. Thiobenzophenone‐S‐oxide (I) and 4,4′‐dimethoxythiobenzophenone‐S‐oxide (II) were obtained by oxidizing the corresponding thioketone with less than one equivalent of monoperphthalic acid. The oxidation of thiaxanthione appeared to give three types of sulfines, viz., IV, V, and VI, the formation of which was rationalized. Factors controlling the stability of sulfines are discussed and also the mechanism of the oxidation of the magnified image moiety with peracid. The alternative route to sulfines, viz., elimination of hydrogen chloride from sulfinyl chlorides, is described for thiofluorenone‐S‐oxide, thiobenzophenone‐S‐oxide and 2‐methoxynaphthalene‐1‐thial‐S‐oxide. In the latter case the originally published yield of 18% was increased to 63%. In addition to this sulfine the sulfinyl sulfone XI was isolated as a by‐product which loses sulfur dioxide on heating giving the sulfoxide XII.