Halogenation of Isothiocyanates

The chlorination of isothiocyanates is the classical synthesis of carbonimidoyl dichlorides. Sell and Zierold in 1874 obtained phenyl-carbonimidoyl dichloride (IX) upon chlorination of phenyl isothiocyanate in chloroform at 0°C, and Nef ( ° ) observed that under the conditions 

Phenylcarbonimidoyl dichloride To a solution of 67.5 g (0.5 mole) of phenyl isothiocyanate in 200 ml of carbon tetrachloride chlorine is added with stirring and ice-cooling below 3°C until the chlorine is no longer absorbed (approximately three to four hours). The solvent and sulfur dichloride, formed in the reaction, are removed by distillation, and vacuum distillation of the residue yields 74-78 g (85-90%) of phenylcarbonimidoyl dichloride, b.p. 103-106°C (31 mm). 

In the aliphatic series, the chlorination of isothiocyanates proceeds exceedingly well, provided that the crude reaction products are treated with aqueous sodium sulfite and sodium carbonate in order to remove impurities which can give rise to decomposition during vacuum distillation ( ). 

In addition to isothiocyanates, compounds having the configuration RN=C(SX)2 (X = alkyl or K) react rapidly with chlorine to produce carbonimidoyl dichlorides. Thus, Neidlein and his co-workers and Gompper and Kunz ( )obtained arylsulfonylcarbonimidoyl dichlorides X in the reaction of S,S-dialkyl-N-sulfonyldithiocarbonimides XI with chlorine. 

Methanesulfonylcarbonimidoyl dichloride ). To a solution of 19 g of S,S-dimethyl N-methanesulfonylcarbonimide in 180 ml of glacial acetic acid chlorine is added below 15°C with cooling for a period of one hr. Evaporation of the solvent and vacuum distillation of the residue yields 14 g (83%) of methanesulfonylcarbonimidoyl dichioride, m.p. 73-76°C (m.p. 79-80 C is listed in Reference 95 the b.p. can not be established because the compound sublimes under vacuum). 

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