Reaction of a nucleobase with nitrosonium ion leads to its diazotization. Due to the instability,the nucleobase-diazonium assumingly falls in dediazotization and successive ring openingreactions. The resulting intermediate of the ring opening reaction is able to covalently cross-linkthe opposite strands of DNA. To examine this assumption for cytosine, some 4-amino-5-cyanopyrimidines were synthesized via [3+3] condensation of amidines with ethoxymethylenemalonitrile and successively converted to the corresponding 4-amino-5carboxyamido derivatives. These compounds were then exposed to nitrosonium ion under different conditions. Results of this study indicate that the diazonium of a 4-aminopyrimidine prefers deamination over the dediazotization. Therefore, the dediazotization and its successive ring-opening reactions of the pyrimidine cation would happen under some exceptionalconditions which deserve to be explored in more detailed studies. In view of the cytosinechemistry and cytotoxicity of NO, the results are presented and discussed. تفاصيل المقالة

A simple, green and efficient method for synthesis of 2,4,5-trisubstituted imidazoles is described via three-component cyclocondensation of benzil or benzoin, aldehyde and ammonium acetate by using the nano SiO2-supported ferric hydrogen sulfate (FHS/SiO2), as a catalyst, under solvent-free conditions. The nano SiO2 support and catalyst were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and IR spectroscopy. In this project, the optimum conditions such as: reaction temperature, reaction time and amount of catalyst were investigated. The major advantages of the present method are high yields, shorter reaction times, easy work-up, purification of products by non-chromatographic method and the reusability of the catalyst. تفاصيل المقالة