Reactions of Halogenated Carbodiimides

N-Trifluoromethyl-N -arylcarbodiitnldes 30 undergo dimerization and trimerization on attempted synthesis to form 31(R = 4-MeOPh, 2,6-Me2Ph) and 32 (R = Ph, 2,6-Me2Ph), respectively. The cycloaddition reactions occur across the aliphatic C=N bond.  

When the reaction is conducted with 2-aminopyridine, the intermediate carbodiimide 33 undergoes a [4 + 2] cycloaddition reaction to form the triazine derivative 34. 

The Q -chlorocarbodiimides 35, in the presence of N-ethyl-N,N-diisopropylamine, undergo a cyclocondensation reaction with 2-benzimidazolylacetonitriles at room 

The reaction of bis-a-chlorocarbodiimides with 37 with alcohols, phenols or carboxylic acids in the presence of triethylamine affords the expected substitution products 38 and 39. However, reaction with amines gives diazadiene derivatives 40.  

On heating of the carbodiimide 41 in toluene a [2 + 4] cycloaddition occurs giving rise to the formation of 4-imino-l,3-benzoxazins 42. This reaction is the first example of an intra-molecular electrophilic substitution on the benzene ring by a carbodiimide group.  

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