1,2,3-Trithiole 2-oxide, 4,5-dicyano

Dicyano-l,2,3-trithiole 2-oxide (143) has been prepared from the silver salt of 2,3-dimercaptomaleonitrile (142) and thionyl chloride (66HC(2l-i)67). Similarly, the reaction of ethylene glycol (144) with thionyl chloride gave 1,3,2-dioxathiolane 2-oxide (145), the parent compound of saturated five-membered cyclic sulfites (see Chapter 4.33). 

The synthesis of 4,5-dicyano-l,2,3-trithiole 2-oxide (172) starts from sodium cyanide and carbon disulfide which via (170) gave the disodium salt of 2,3-mercaptomaleonitrile (171 M = Na). Treatment of the corresponding silver salt (171 M = Ag) with thionyl chloride yielded (172) <66HC(2l-l)l). Phenylsulfine (174), prepared in situ by dehy-drohalogenation of phenylmethanesulfinyl chloride (173), slowly decomposed in ether solution at room temperature to give cis- and trans-stilbenes, mms-4,5-diphenyl-l,2,3-trithiolane 1,1-dioxide (36) and a 5,6-diphenyl-l,2,3,4-tetrathiane dioxide (68JCS(C)1612). The mechanisms of formation of these heterocycles are obscure. 

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