Thiazetidines and Thiazetes

Thiazetidines and Thiazetes.—Kinetic data for the c cloadditions of dicyclo-hexylcarbodi-imide with pora-substituted phenyl isothiocyanates to give 1,3-thiazetidine derivatives (68) (yields of 31—92%) have been obtained for both 

3-aryl-1,2-thiazetidine 1,1-dioxide (69). Thermolysis of the 3,4-diphenyl derivative gave tra/w-stilbene, and ring-opening occurred on treatment with sodium methoxide, 

Hull and D. J. H. Smith, Organic Sulphur Chemistry , ed. C. J. M. Stirling, Butter-worths, London, 1975, p. 364. 

The action of hydrogen peroxide-acetic acid on 2-imino-l,3-thiazetidines gives ring-expanded products, viz. 3-oxo-l,2,4-thiadiazolidine 1-oxides, presumably via the thiazetidine 1-oxide. The polymerization of 1,2-thiazetidine 1,1-dioxide has been studied.  

Le Berre, A. fitienne, and B. Desmazi res, Bull. Soc. chim. France, 1976, 277 ibid., 1975, 

Thiazetidines and Thiazetes.— The reaction of sulphur di-imides with ketens leads ultimately to 1,2-thiazetidine derivatives (1 by way of intermediates (185) and (186). Oxidation of (187) with m-chloroperbenzoic acid leads to the S-oxide (188). The 1,2-thiazetidine intermediate proposed to account 

Langendries and F. C. De Schryver, Tetrahedron Letters, 1972,4781 O. L. Chapman, XXIII Internal. Congress Pure and Applied Chemistry, Boston, Mass., July 1971, Butter-worths, London, 1971, vol. 1, p. 330. 

2-Thiazetidine 1,1-dioxides (192) are obtained by treatment of olefins with salts of methoxycarbonylsulphamoyl chloride (190) or with oxathiadiazines (191). Electron-rich olefins yield thiazetidine dioxides 

Good yields of 1,3-thiazetidmes (202) are obtained by treatment of the unsynunetrically substituted thioureas (201) (in which hydrogen-bonding appears necessary for success) with di-iodomethane. The formation and properties of some other 1,3-thiazetidines have been surveyed. Photolysis of a mixture of a thioketone and a nitrile yields N-thioacylketimines, possibly via a thiazete. Another thiazete was discarded as a possible intermediate in the acyl migration from sulphur to nitrogen observed in S-benzoylisothiouronium salts.  

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The present review is concerned with four-membered heterocycles that contain one sulfur atom either alone or associated with another heteroatom. The classes of compounds that will be discussed are the thietanes (1) and thietes (2), the 1,2-oxathietanes (3), the / -sultines and -sultones (4 and 5), the 1,2- and 1,3-thiazetidines (6 and 7) and thiazetes (8), the 1,2- and 1,3-thia-phosphetanes (9 and 10), and the 1,3-silathietanes and 1,3-selenathietanes (11 and 12). 

Thiazetidines and their Derivatives.—Cyclization reactions yield (140) from benzenesulphonyl isocyanate and a thioamide, (141) from aroyl isothiocyanates and DCCI, (142) from dihydroisoquinoline and the CSj adduct of a Wittig reagent,and (143) from the BF3 EtjO-catalysed reaction of ethylenethiourea and aryl aldehydes. Thiazet (144) reacts with SbjTcs, presumably through the open thione-imine form, to give (145). 1,3-Thiazetidines have been proposed as intermediates. ... 

Spectra of thiazetidines have been recorded by Gallow and Klaeser. The 1,3-thiazete 45 and its tautomer 46 produced the following fragmentation pattern. 

Intramolecular cyclization of iV-cyanodithiocarbamic acid leads to the formation of 2-thio-4-amino-l,3-thiazete (183) and its tautomer 2-thio-4-imino-l,3-thiazetidine (182) (Eq. 38). The four-membered heterocycle is a finely crystalline, red-colored compound that decomposes at 172°C. 

A-(Alkylsulphonyl)imides (138), prepared by treating A-alkylsulphamoyl chlorides with Et3,N, react with enamines that bear no hydrogens jS to the morpholino-group to give 1,2-thiazetidine 1,1-dioxides (139). The preparations and e.s.r. spectra of two relatively stable l,2-thiazet-2-yl radicals have been reported. ... 

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