Synthesis of Nitrogen Substituted Carbodiimides

The reaction of the N,N-dimethylamino semicarbazide derivative 1 with phosgene affords the chloroformamidine intermediate 2, which on treatment with sodium bicarbonate affords N-t-butyl-N -dimethylaminocarbodiimide 3, bp 150 °C in 64 % yield.  

On standing at room temperature, 3 undergoes dimerization to form two isomeric hetero-cyclic zwitterionic dimers. N-phenyl-N -dimethylaminocarbodiimide could not be obtained under similar conditions in pure form. 

Reaction of diethyl N-dimethylaminophosphoramidate with t-butyl- or t-octyl isocyanate affords the corresponding carbodiimides 4 in 60 % yield.  

The N-aminosubstituted carbodiimides 4 slowly dimerize on standing. Heating of the dimers regenerates the monomers. 

The reactions of N-substituted iminophosphoranes 5 with alkyl or aryl isocyanates proceed under mild conditions to give aziridin substituted carbodiimides 6 (R = H, Ph R = Me, Ph, a-naphthyl), which are only observed in solution, and their yield is 

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