Synthesis of Isocyanates and Carbodiimides

Abstract

Abstract The reaction of 1,3‐disubstituted ureas and 1‐arylsulfonyl‐3‐alkylureas with phosgene permits the preparation of a number of isocyanates and sulfonyl isocyanates that had not previously been described, or that were difficult to prepare. 1,3‐Disubstituted thioureas and 1‐aryl‐(or alkyl)sulfonyl‐3‐alkylthioureas give carbodiimides. Thionyl chloride and phosphorus pentachloride react with the urea derivatives in the same way as phosgene. Oxalyl chloride reacts with ureas to form parabanic acid derivatives, whereas with thiourea it gives 2‐imino‐1,3‐thiazolidine‐4,5‐diones, which can isomerize to parabanic acid derivatives.