Thioxanthones, Selenoxanthones, and Related Compounds

Thioxanthones (83 X = S, R = CO Me or NH2) have been synthesized by cyclization of appropriate thiosalicylic acid derivatives. Seleno-xanthone (83 X = Se, R = H), prepared from the acid chloride (84) by o 

Thioxanthenes with basic side-chains have been prepared for pharmacological evaluation, and a series of 0-alkyl, O-acyl, and 0-carbamoyl derivatives of thioxanthydrol have been described.  

It has been shown that the product obtained by the action of phosphorus pentachloride on thioxanthone is the thioxanthylium salt (85). Reduction of thioxanthylium perchlorate with zinc (in the absence of oxygen) gives the bimolecular product (86), but with 9-phenylthioxanthylium perchlorate 

Svatek, J. Metysova, F. Hradil, and M. Protiva, Coll. Czech. Chem. Comm., 1970, 35, 2623. 

Other papers on thioxanthene derivatives deal with the methylation, on sulphur and sulphoxide-oxygen respectively, of thioxanthene and thio-xanthone sulphoxide, the Beckmann rearrangement of thioxanthone oxime, and the quantitative reduction of thioxanthene sulphoxide to thioxanthene with sodimn borohydride-cobalt chloride, a reagent which appears to be of fairly neral applicability.  

---