Preparation of Nuclear Halogenopyrazines

With the exception of those halogenopyrazines made by primary synthesis (see Chapters 1 and 2), most chloropyrazines have been made recently by the reaction of tautomeric pyrazinones with a phosphorus chloride or by the reaction of pyrazine iV-oxides with phosphoryl chloride in contrast, most other halogenopyrazines have been made by direct halogenation or by transhalogenation of chloropyrazines. A single interesting example of the conversion of a methoxy- into a chloropyrazine is included at the end of Section 4.1.1. 

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