From Thioureas or Ureas

The dehydrosulfurization of l-arenesulfonyl-3-alkylthioureas with HgO affords the corresponding N-sulfurcarbodiitnides only in low yields (8-14 %). However, reaction of 

Chemistry and Technology of Carbodiimides Henri Ulrich 2007 John Wiley Sons. Ltd. ISBN 978-0-470-06510-5 

Better results are obtained using carbonyl chloride or phosphorous pentachloride in the reaction with the sulfonylthioureas. Intermediates in this reaction are chloroformamidines 1, which, on heating, eliminate hydrogen chloride to give N-sulfonyl-N -alkylcarbodiimides 2. 

Similarly, N-p-toluenesulfonyl-N -cyclohexylcarbodiimide is obtained from the corresponding thiourea in 65 % yield.  

The dehydrochlorination of 1 can also be achieved using aqueous base. Bis(arenesulfonyl)carbodiimides are intermediates in the reaction of the corresponding chloroformamidines with hydrazine.  

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