Oxidation of 1,4-dihydropyridines under mild and heterogeneous conditions using solid acids

A combination of solid acids, including Oxone(R), HIO3, H5IO6, and polystyrenesulfonic acid and sodium nitrite, in the presence of wet SiO2 were used as an effective oxidizing agents for the oxidation of dihydropyridines to their corresponding pyridine derivatives under mild and heterogeneous conditions in good to excellent yields.