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Thioxanthone is a heterocyclic compound that is a sulfur analog of xanthone.
Thioxanthone can be prepared by the reaction of diphenyl sulfide with phosgene in the presence of catalytic aluminium chloride. This synthesis can be seen as a special case of the Friedel-Crafts acylation. The reduction product is thioxanthene.
Thioxanthone dissolves in concentrated sulfuric acid to give a yellow colored liquid with intense green fluorescence. A mixture of the thioxanthone derivatives of 2- and 4-isopropylthioxanthone (ITX) is used in the printing industry. Pharmaceutical drugs that are derivatives of thioxanthone include hycanthone and lucanthone.

slightly yellow crystalline powder

Thioxanthen-9-one is a reagent and a starting material for the synthesis of Metixene Hydrochloride. It is also used for highly functional group tolerant and chemoselective oxidation of aromatic or aliphatic sulfides to sulfoxides with hydrogen peroxide.

Tetrahedron Letters, 35, p. 2195, 1994 DOI: 10.1016/S0040-4039(00)76794-3

It forms yellow needles from CHCl3 or EtOH and sublimes in vacuo. It is soluble in CS2, hot AcOH, and dissolves in conc H2SO4 to give a yellow colour with green fluorescence in VIS light. The sulfone has m 187o (from EtOH), and the hydrazone has m 115o (yellow leaflets from EtOH/*C6H6). The oxime has m 194-196o (from pet ether). [Szmant et al. J Org Chem 18 745 1953, Ullmann et al. Chem Ber 49 2509 1916, NMR: Sharpless et al. Org Magn Res 6 115 1974, Beilstein 17 H 357, 17 I 191, 17 III/IV 5302, 17/10 V 437.]