THERMAL INTRA-MOLECULAR HYDROXYLATION REACTIONS INVOLVING 5-NITRO-PYRIDINE N-OXIDE DERIVATIVES

The N-oxides of 5-nitro-2-(aryloxy)pyridine, e.g. (2), undergo rearrangement on heating in an inert solvent to produce, as the major product, the corresponding 5-nitro-2-(2′-hydroxyaryloxy)pyridine, e.g. (4). Competition experiments indicate an intramolecular transfer of oxygen. The product (4) can be cleaved by hydrazine to produce the corresponding pyrocatechol and the scope of the net transformation, phenol to catechol, is briefly explored. Certain metals, in particular vanadium, affect the ratio of phenols produced.