Using unlabeled data for supervised learning
4-(3-Nitrophenyl)pyridine, an intermediate useful in the preparation of 1-(lower-alkyl)-1,4-dihydro-4-oxo-7-(4-pyridyl)-3-quinolinecarboxylates, which are useful as antibacterial agents, is prepared by reacting 3-nitrobenzaldehyde with two molar equivalents of di-(lower-alkyl) oxalacetate (II) in the presence of a catalytic condensing agent, preferably piperidine and/or its acetate, to produce tetra-(lower-alkyl) 3-(3-nitrophenyl)-1,5-pentanedione-1,2,4,5-tetracarboxylate (III), reacting III with ammonia to produce tetra-(lower-alkyl) 1,4-dihydro-4-(3-nitrophenyl)-2,3,5,6-pyridinetetracarboxylate (IV), oxidizing IV to produce tetra-(lower-alkyl) 4-(3-nitrophenyl)-2,3,5,6-pyridinetetracarboxylate (V), hydrolyzing V to produce 4-(3-nitrophenyl)-2,3,5,6-pyridinetetracarboxylic acid (VI) and decarboxylating VI to produce 4-(3-nitrophenyl)pyridine (VI). Intermediates III, IV, V and VI are novel.