Reactivity of 4‐nitropyridine‐N‐oxide: Preparation of 4‐substituted derivatives of pyridine‐N‐oxide and pyridine

It is shown that the nitro‐group in 4‐nitropyridine‐N‐oxide can be readily replaced by negative ions and that the N‐oxides thus obtained, can be reduced quantitatively to the corresponding pyridine derivatives. This fact reveals an excellent method for the preparation of several 4‐substituted pyridine‐N‐oxides and pyridines. It is all the more useful, since the synthesis of 4‐nitropyridine‐N‐oxide has been simplified. The preparation of 4‐bromo‐, 4‐chloro‐ and 4‐ethoxypyridine‐N‐oxide is described in detail.