Amidines 5-nitropyrimidines

Another approach uses the reaction of 6-chloro-5-nitropyrimidines with a-phenyl-substituted amidines followed by base-catalyzed cyclization to pteridine 5-oxides, which can be reduced further by sodium dithionite to the heteroaromatic analogues (equation 97) (79JOC1700). Acylation of 6-amino-5-nitropyrimidines with cyanoacetyl chloride yields 6-(2-cyanoacetamino)-5-nitropyrimidines (276), which can be cyclized by base to 5-hydroxypteridine-6,7-diones (27S) or 6-cyano-7-oxo-7,8-dihydropteridine 5-oxides (277), precursors of pteridine-6,7-diones (278 equation 98) (75CC819). 

Experiments with mono- N-labeled amidines (the label is equally scrambled over both nitrogen atoms) have shown that in the 2-R-5-nitropyrimidines the excess of the enrichment is lower than that in the amidine (see Table III.2) (86JOC71). These measurements clearly indicate that during the reaction some labeling is lost. This result leads to the conclusion that besides formation of a mono- N-labeled 2-phenyl-5-nitropyrimidine (108), in which the N-label is scrambled over both nitrogens, a mono- N-labeled 2-phenyl-5-nitropyrimidine (109) is also obtained in which only one nitrogen is N-labeled (the benzamidine acts in this reaction as N-C donor) (Scheme III.55). 

N Content in Amidines and in Products Obtained in the Reaction of 5-Nitropyrimidines with Amidines... 

A variety of amidines react with nitromalonaldehyde in presence of Triton B or piperidine, to form the 5-nitropyrimidines 116 [Eq. (37)].106-110 Yields range from 30 to 90%. Acetamidine gives a very poor yield of the nitropyrimidine and formamidine does not give any isolable product. 

The reaction of 5-nitropyrimidine with amidines to afford 2-substituted 5-nitropyrimidines and 2-amino-5-nitropyridines and a new synthesis of 2-nitroimidazoles have been reported. ... 

Acetic anhydride pyridine 5-Nitropyrimidines from amidines... 

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