3-Nitro-2-pyridones

Methyl-5-nitropyrimidm-4n//)-one reaas v/ith ketones in the presence of ammonittm salts to give 4,5-disubsdntted pyrimidmes or 5,6-disubsdntted 3-nitro-2-pyridones depending on reacdon condidons fEq. 10.83. ... 

Methyl-5-nitropyrimidin-4(3f/)-one reacts with ketones in the presence of ammonium salts to give 4,5-disubstituted pyrimidines or 5,6-disubstituted 3-nitro-2-pyridones depending on reaction conditions (Eq. 10.83).142... 

Scheme 13 TCRT leading to pyrimidines and 3-nitro-2-pyridones...

The precipitated yellow solid during the reaction is 6-phenyl-3-nitro-2-pyridone 28g whose C2 - C3 - C4 unit is derived from the C4 - C5 - C6 unit of pyrimidinone 3. Another TCRT proceeds at the 4- and the 6-positions of pyrimidinone 3, which behaves as the synthetic equivalent of a-nitro-formylacetic acid 29. 

Both pyrimidines [46] and 3-nitro-2-pyridones [48-53] are often found in biologically active compounds or their synthetic intermediates. The present TCRT will be a useful protocol for construction of a useful library, however, it is required to control the selectivity of these products from the viewpoint of atom economy. The addition of acetic acid is influential for the selectivity of this reaction, and the results are summarized in Table 3. 

In the last sections, 3-nitro-2-pyridones 28 are synthesized by TCRT of nitropyrimidinone 3 with ketones 22 in the presence of ammonium acetate. The C2 - C3 - C4 unit of 28 is derived from the C4 - C5 - C6 unit of pyrim-idinone 3, which behaves as the synthetic equivalent of a-nitroformylacetic acid 29. The same partial structure is also found in l,3-dinitroquinolizin-4-one 35 [55], which is regarded as the dinitropyridone blocked with a benzene ring on the [/] face [56], and only a single kind of TCRT is expected to proceed. Nitropyridones 28 are actually prepared in moderate yields by TCRT upon treatment of quinolizinone 35 with ketones 22 in the presence of ammonium acetate as the nitrogen source (Table 7) [57]. 

Nitration of 2-pyridone, originally thought to give mainly 3-nitro-2-pyridone (47) together with some 3,5-dinitro-2-pyridone (48) and a trace of the 5-nitro derivative (49),123 was later shown to give a mixture of 47 and 48.124 Similarly, reaction of 6-methyl-2-pyridone with nitric acid in glacial acetic acid gave the product of nitration at C-3 (50).125 This preferential ortho-nitration is in marked contrast to... 

Nitromalonic ester reacts with enamino-ketones and esters to produce the 4-hydroxy-3-nitro-2-pyridones 85 [(Eq. (26)].76... 

Nitro-2-pyridone exists predominantly in the keto form in DMSO-[Pg.6]

Variations include the use of 3-alkoxy-enones (i.e. the enol ethers of 1,3-diketones) when the initial Michael-type interaction dictates the regiochemistry Using nitroacetamide instead of cyanoacetamide produces 3-nitro-2-pyridones and using H2NCOCH2C(NH2)=N H2 Cl gives 2-aminopyridine-... 

Alkylation of 4-hydroxy-6-methyl-3-nitro-2-pyridone (MI-552, R = H) and its 5-carbethoxy derivative (MI-552 = COj Cj H5) with diazomethane in ether or... 

Since 2-pyridones are nitrated mainly as their free bases and are probably in the pyridone form, °° it is not likely that a transition state involving hydrogen-bond participation by OH as has been suggested for ortho-nitration of phenol and for nitration of 2-substituted-3-pyridinols at the 4-position (this section, p. 809) is responsible for the formation of 3-nitro-2-pyridone, the major product. ... 

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