The chemistry of aromatic amine oxides, of which pyridine N-oxide is a representative compound, has re- ceived much attention for several decades.' From the standpoint of organic reactions theory, the fundamental issue in N-oxide substituent effects is that the substituent has an electron-supplying effect for the pyridine ring due to the resonance A and an electron-withdrawing effect due to B.2 The a and y positions of the ring are said to be ... (1) For examples, (a) ...