Reactions of N-polyfluorophenylcarbonimidoyl dichlorides with primary and secondary amines. Kinetics and mechanism. Synthesis of polyfluorinated carbodiimides, chloroformamidines, guamidines and benzimidazoles.

Abstract

The reaction of N-polyfluorophenylcarbonimidoyl dichlorides with primary and secondary aliphatic and aromatic amines have been studied. With primary aliphatic amines, the reactions led to carbodiimides or guanidines, depending on the amount of amine. The carbodiimides obtained reacted with amines to form guanidines. The reactions with primary aromatic amines produced only triarylguanidines. N-Pentafluorophenyllcarbonimidoyl dichloride (I) reacted with tetrafluoro-o-phenylene diamine to give 2-pentafluoroanilino-4,5,6,7-tetrafluorobenzimidazole. Polyfluorinated benzimidazole derivatives were also produced by the thermolysis of polyfluorinated triarylguanidines. Heating of N 1,N 2,N 3-tris(pentafluorophenyl)guanidine with K 2CO 3 in dimethylformamide led to 1,2,3,4,7,8,9,10-octafluoro-5-pentafluorophenyl-5H-benzimidazol[1,2-a]benzimidazole. N-Polyfluorophenylcarbonimidoyl dichlorides reacted with various secondary amines already at room temperature giving N-polyfluorophenylchloroformamidines in high yields. Elevated temperature and prolonged reaction time led to formation of N-polyfluorophenylguanidines. Kinetics and mechanism of the reactions of N-polyfluorophenylcarbonimidoyl dichlorides with primary and secondary amines in acetonitrile at 25°C have been studied. The reactions have been found to proceed by a bimolecular nucleophilic addition-elimination mechanism via a tetrahedral intermediate. Possible reasons of formation of different products in the above transformation are discussed in terms of this mechanism.