A novel application of the oxidizing properties of urea nitrate and peroxydisulfate-cobalt(II): aromatization of NAD(P)H model Hantzsch 1,4-dihydropyridines

4-Alkyl or aryl substituted derivatives of Hantzsch 1,4-dihydropyridine were readily oxidized by urea nitrate under microwave irradiation or refluxing conditions to the corresponding pyridine derivatives in quantitative yields. The oxidation reaction was also effected by peroxydisulfate in the presence of cobalt(II) in aqueous acetonitrile under refluxing conditions. When n-propyl, n-butyl and cinnamyl were the substituent groups in the 4-position, a mixture of 4-substituted and unsubstituted pyridines were formed. The catalysts used in the reaction are inexpensive and provide high yields in short reaction times. (C) 2002 Elsevier Science Ltd. All rights reserved.