Thiet and its Derivatives

Formation.—Phenyl-, 2-naphthyl-, 2-thienyl-, and 2-furanyl-thiets are prepared from aryl methyl ketones, dimethylamine, and methanesulphonyl chloride. X-K y crystal structures establish that the compounds arising from the cycloaddition of alkynes to thioxanthones are thiets, and not spiro-dihydropyrans, as originally proposed. Additional work shows that alkynyl sulphides also give thiets with thioxanthone, and that the adduct (104) is in rapid equilibrium with the open form (105) in solution, although they can be isolated separately. Thiet (106) was isolated after thermolysis of a Dewar thiophen—azide adduct.  

A potentially useful reaction for the large-scale preparation of benzothiet (107) has been reported. It involves the thermolysis of (108) at 700 C and is estimated to 

Dittmer, in New Trends in Heterocyclic Chemistry , ed. R. B. Mitra, Elsevier, Amsterdam, 1979. 

Gotthardt and O. M. Huss, Tetrahedron Lett., 1978, 3617 cf. H. Gotthardt and S. Nieberl, ibid., 

Thiet sulphones are prepared by elimination reactions of the appropriate thietan sulphones.  

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