Benzonitriles, halogen-substituted, reduction

The amine group in primary amines can be replaced by halogen by warming the benzoyl derivative with phosphorus pentachloride or phosphorus pentabromide. Oftentimes, the separation of the halide from the benzonitrile, which is also formed, is troublesome. The process has been applied mostly to high-moIecuIar-weight amines obtained by the Hofmann degradation of acid amides or by reduction of nitriles." Diamines lead to dihalogen derivatives." If N-benzoyl piperidines are treated, substituted pentamethylene halides are formed. An example is the synthesis of pentamethylene bromide by the action of phosphorus pentabromide on N-benzoyl piperidine (72%). ... 

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