Synthesis of Six-Membered Nitro-Heterocycles

Most of the reported ring syntheses of nitropyridines result in the nitro group occupying position 3 of the pyridine nucleus. Only two reactions have been reported for 4-nitropyridines, of which one leads to a 2,4,6-trinitro-pyridine. 

The reaction of enamino-ketones with nitroacetic ester at 60° has been shown to generate the 3-nitropyridones (81) [(Eq. (25)].72 

The sodium salt of nitromalonaldehyde reacts with /J-aminocrotonic ester to give 2-methyl-5-nitronicotinate (82).7 3 

Surprisingly, a preference for the formation of a pyridine rather than a pyrimidine ring is shown in the reaction of sodio-nitromalonaldehyde with ethyl formamidinoacetate the product is ethyl 2-amino-5-nitronicotinate (83).74 

The condensation of sodio-nitromalonaldehyde with cyanoacetamide in the presence of Triton B gives 3-cyano-5-nitro-2-pyridone (84) (93%).75 

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