Cyanogen, reaction with sulfur monochloride

Cyanoformamide (40), formed in quantitative yield by the acid-catalyzed reaction of cyanogen with water, is converted into 3-chloro-4-hydroxy-l,2,5-thiadiazole (41) by reaction with sulfur monochloride.Prior conversion of 40 to the imino ether (42) leads to 3-ethoxy-4-hydroxy-l,2,5-thiadiazole (43). 

Cyanogen itself is reported to react smoothly with sulfur monochloride to form 3,4-dichloro-l,2,5-thiadiazole 37. The reaction was not exothermic and was readily run by passing cyanogens into an S2CI2 solution in dimethylformamide at 80 °C (1967JOC2823 Scheme 21). 

The reaction products of cyanogen with alcohols, dialkyl oximidates (44) and alkylcyanoformimidates (45), also available through the reaction of sodium cyanide with chlorine in aqueous alcohol, both react with the sulfur chlorides forming the appropriately substituted thiadiazole. Wen reported the synthesis of diethoxy-1,2,5-thia-diazole (46) from 44 and sulfur dichloride. Several analogs of 45 were converted to 3-chloro-4-alkoxy-l,2,5-thiadiazoles (46a) by treatment with sulfur monochloride. 

A number of useful syntheses of 1,2,5-thiadiazoles from cyanogen and its derivatives have been reported all of which proceed in high yield. 3,4-Dichloro-l,2,5-thiadiazole (39) was prepared by reaction of cyanogen with sulfur dichloride or sulfur monochloride. Unlike... 

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