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The interaction of α,β-unsaturated nitro ketones and various enamines leads to the synthesis of 5-nitro-1,4-dihydropyridines containing acetyl, amide, benzoyl, ester, and cyano groups in position 3, and also unsymmetrical 3,5-dinitro-1,4-dihydropyridines. Aromatization of the nitrodihydropyridines was carried out with sodium nitrite in acetic acid.The synthesis of nitropyridines by the Hantzsch reaction is effected by the cyclocondensation of α,β-unsaturated nitro ketones (condensation products of aromatic aldehydes with nitroacetone and nitroacetophenone) with various enamines.The availability of nitroacetone and nitroacetopheone enables them to be considered as valuable raw materials in the synthesis of nitropyridines [2], possessing potential biological activity.Nitroacetone [3,4] and nitroacetophenone [5] used in the work were obtained by the condensation of nitromethane with acetaldehyde and benzaldehyde (the Anri reaction). The nitroalcohols obtained were oxidized with sodium dichromate.The condensation of nitroacetophenone with aromatic aldehydes proceeds readily and the corresponding nitrochalcones 1 are formed in preparative yield [6].Nitroacetone may interact with aromatic aldehydes at both the methyl and the methylene group. Under alkaline catalysis conditions the aldol condensation product is formed only at the methyl group. To obtain condensation products at the methylene group a less reactive Schiff's base of the aromatic aldehyde is used. In this way condensation products at the methylene group are formed in good yield only in the reaction of nitroacetone with Schiff's bases of an aromatic aldehyde containing an acceptor group in the nucleus [7], the yield of 2-nitro-1-phenyl-1-buten-3-one 1a was only 26%. Because of the low yield of chalcone 1a, the cyclocondensation of benzylideneacetoacetic ester with the enamine of nitroacetone 2f was used for the synthesis of nitrodihydropyridine 3d (variant B) (Scheme 1).The condensation of benzylidenenitroacetone 1a with aminocrotonic ester (variant A) in acetic acid at room temperature and an equimolar ratio of initial reactants leads to nitrodihydropyridine 3d in 56% yield. On condensation by variant B under analogous conditions pyridine 3d is formed with a yield of 40%. We also note that the enamine of nitroacetone 2f [8], obtained by the transamination of 2-dimethylamino-1-nitro-1-propene _______ * For Part 1 see [1]. __________________________________________________________________________________________

Cadogan reductive cyclization of substituted 2-aryl-3-nitropyridines to give δ-carbolines was performed under MoO2Cl2(DMF)2 catalysis with triphenylphosphine as a ligand. A new approach for the synthesis of the alkaloid quindoline based on a Mo(VI)-catalyzed Cadogan reductive cyclization of 2-phenyl-3-nitro-5,6,7,8-tetrahydroquinoline followed by aromatization of the resulting 2,3,4,10-tetrahydro-1H-indolo[3,2-b]quinoline is proposed. Various о-nitroarylpyridines, obtained by reacting acylpyruvates and cyclic hydroxymethylene ketones with nitroacetophenone enamines, were used as starting compounds for the preparation of δ-carbolines. The synthesized δ-carbolines were found to act as phosphors; their photophysical properties were studied and a structure–property relationship was revealed.

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