Oxidative aromatization of novel tetrahydrochromeno[4,3-b]quinolines using silica sulfuric acid/NaNO2

A combination of silica sulfuric acid and sodium nitrite in the presence of wet SiO2 was used as an effective oxidizing agent for the oxidative aromatization of novel Tetrahydrochromeno[4,3-b]quinolines to their corresponding pyridine derivatives under reflux and heterogeneous conditions in high yields.