Rearrangement of Nitropyridylidenemalonate 1-Oxides. A Novel Method for the Synthesis of Aminopyridine Derivatives

Knoevenagel condensation between 3-nitro-2-pyridinecarbaldehyde and diethyl malonate catalyzed by titanium(IV) chloride gave diethyl 3-nitro-2-pyridylidenemalonate which was oxidized with peracetic acid to give corresponding 1-oxide. Reaction of the latter with diethylamine in the presence of primary and secondary alcohols resulted in the reduction of the nitro group and the oxidation of the vinylic carbon attached to the pyridine ring. Simultaneous migration of the malonic fragment gave the appropriate 3-amino-2-pyridinecarboxylate esters. The 4-nitro-3-pyridylidenemalonate 1-oxide rearranges into the corresponding 4-amino-3-pyridinecarboxylate analogue.