Pyrimidine-2-acetonitrile 1-oxides

The synthesis of (LVII) is accomplished by formylation of p-(acetamido-phenyl)acetonitrile, followed by conversion to the methoxymethylene derivative with diazomethane, condensation with thiourea to give 2-mercapto-4-amino-5-(p-acetamidophenyl)pyrimidine, and oxidation by peroxide, followed by hydrolysis in base to produce (LVII) [347]. Alternatively, 5-phenylcytosine can be nitrated and reduced [348]. 

Thermal decarboxylation of pyrimidylcarboxylic organotin esters is another means to prepare the corresponding stannylpyrimidines [33]. This method obviates the intermediacy of lithiated pyrimidine species that would undergo undesired reactions at higher temperatures. The decarboxylation occurs at the activated positions. Therefore, thermal decarboxylation of tributyltin carboxylate 62, derived from refluxing carboxylic acid 61 with bis(tributyltin) oxide, provided 4-stannylpyrimidine 63. Addition of certain Pd(II) complexes such as bis(acetonitrile)palladium(II) dichloride improved the yields, whereas AIBN and illumination failed to significantly affect the yield. 

The second patent by Upjohn describes an improved route, obviating the use of the sealed tube reactor (Scheme 6). Therefore, 6-amino-4-chloro-2-imino-2H-pyrimidin-l-ol (28) was prepared from the oxidation of 4-chloro-pynmidine-2,6-diamine (27). The crude product was extracted with boiling acetonitrile to give pure 28 in 44.7% yield. Refluxing 28 with excess of piperidine for 1.5 h then afforded minoxidil (3) after extraction with boiling acetonitrile. 

Photolysis (10 h) of l,3-dimethyl-5-nitro-6-(l-methyl-2-acetophenyli-denehydrazino)pyrimidine-2,4-dione (71b) in acetonitrile gave an excellent yield of 2,6-dioxo-l,3,9-trimethyl-8-azapurine 7-JV-oxide (72). This product was apparently formed by the addition of a photoexcited NO2 group across the exocyclic double bond, followed by rearrangement of the tricyclic (dioxatriaza) product. ... 

Van et al. [197] studied the electrochemical behavior of pyridazine using cyclic voltammetry in acetonitrile with different supporting electrolytes. Dark, greenish-blue polypyridazine formed on the anode when either lithium perchlorate or ammonium tetrafluoroborate was used as the supporting electrolyte. Also investigated were variations in the acidity of the solution during the course of electrolysis and the effects of the synthetic conditions on the electrochemical and other properties of the films. The pyridazine rings are believed to be para linked and the perchlorate or tetrafluoroborate counteranions are present in a 2 1 molar ratio. Two isomers of pyridazine—pyrazine and pyrimidine—could also be oxidized, but these isomers yielded only yellowish, powdery precipitates and no films. 

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