Anodic oxidation of 4-(o-nitrophenyl)-1,4-dihydropyridines and reductive cyclization of the resulting o-nitrophenyl-pyridines

Abstract

In hydroalcoholic medium, electrochemical oxidation of Nifedipine and its N-methyl derivative on one hand and of the analog 3,5-dicyano-2,6-dimethyl-4-(o-nitrophenyl)-1,4-dihydropyridine and its N-methyl derivative on the other leads to the corresponding o-nitrophenyl-pyridines or pyridinium salts. High yield macroscale electrolyses are carried out in a flow cell at a graphite felt anode. Subsequent reductions of the nitrophenyl-pyridines or pyridiniums give new tricyclic compounds: N-hydroxy-benzo(c)-naphthyridinones from the ester derivatives and reducible amino-N-oxy-benzo(c)-naphthyridines from the cyano compounds.