Uretone imines

Carbodiimide functionality can be produced by reacting isocyanates at elevated temperature with proper catalysis (Scheme 4.15). Although carbodiimides undergo a variety of reactions,23 most commonly as dehydrating agents, in the presence of excess isocyanate they will form uretone imines. This not only increases the average functionality of the isocyanate product but also lowers its freezing point. For example, a liquefied (or modified) version of 4,4,-MDI can... 

Scheme 4.15 Carbodiimidization of isocyanates and formation of uretone imines.

Carbodiimides can react with additional isocyanate groups to form uretone imines, which sometimes are used to modify polyisocyanates used in urethane structural adhesives. 

The reaction of a uretone imine with phosgene proceeds via ring opening to give a chloroformamidine [615a] ... 

The reaction of the uretone imine XXXIX (R = ethyl) with carbonyl chloride proceeds via ring opening with formation of the chloroformamidine XL(i ). 

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