PERISELECTIVITY BETWEEN THE [1,4] AND [3,3] THERMAL SIGMATROPIC REARRANGEMENTS OF 2-ALLYLOXYPYRIDINE N-OXIDES

Thermal rearrangement of 2-allyloxypyridine N-oxides (4a-c) yields N-allyloxy-2-pyridones (5a-c) and 3-allyl-N-hydroxy-2-pyridones (6a-c). These transformations are shown to be regiospecific and on this basis it is proposed that the reactions involve concerted [1,4] and [3,3] sigmatropic rearrangements. Supporting evidence based on solvent effects, temperature effects, and substituent effects is given.