From Carbamates and Thiocarbamates

By analogy with the general synthesis of imidoyl chlorides it can be expected that carbamates and thiocarbamates undergo reaction with a variety of acid halides to afford 1-haloformimidates and 1-halothio-formimidates, respectively. For example, carbamates have been reacted with carbonyl chloride ( ), pyrocatecholphosphorus trichloride ( ), and phosphorus pentachloride ( ), and isocyanates were obtained. In view of the catalytic effect of N,N-dimethylformamide in the phosgenation of carbamates to isocyanates, the intermediacy of 1-chloroformimidates X is anticipated ( ). 

The thermolysis of 1-chloroformimidates to isocyanates and alkyl halides occurs quite readily ( ), thus explaining the formation of the isolated isocyanates. Of course, dithiocarbamates react more readily, and Eilingsfeld and Mobius have synthesized a large number of 1-chlorothio-formimidinium chlorides by treating N,N-disubstituted dithiocarbamates with phosgene or phosphorus pentachloride. 

1-Chlorothioformimidinium chlorides general procedure) C ). To the solution of 1 mole of the N,N-disubstituted dithiocarbamate in 400-700 ml of toluene at 20-30°C approximately 1.5-2.0 moles of phosgene is added. After standing for several hours at room temperature, dry diethyl ether is added and the obtained 1-chlorothioformimidinium chlorides are collected by filtration. The obtained yields range from 72-100%. 

The compounds thus obtained are very hygroscopic and moisture has to be excluded during the work-up. 

The corresponding cyclic dithiocarbamates (2-mercaptothiazoles) are phosgenated in a similar manner to afford 2-chlorothiazolidinium salts For example, from 2-thioxo-3-methylthiazolidine (XI) and 

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