Abstract:

For many years now, the chemistry of 1,2,4- triazolo[1,5-a]pyrimidine derivatives has been of considerable interest for applications in the areas of medicinal and agricultural chemistry. The synthesis of triazolopyridines from the cyclocondensation of aminotriazole and 1,3- dieletrophiles, such as enaminones, chalcones, dicarbonyl, and substituted vinyl ketones, is conventionally performed in the reflux of acetic acid, acetonitrile, ethanol, or pyridine/HCl. However, significant variations in yields and reaction times limit the choice of substrates that can be utilized. Consequently, the development in the last few years of synthetic protocols employing ultrasound irradiation has led to an important change in organic reactions and has permitted the activation of substrates with poor reactive properties. Considering the importance of triazolo[1,5- a]pyrimidine and the restrictions to its synthesis, in this paper we present an efficient approach to the highly regioselective synthesis of 1,2,4-triazolo[1,5- a]pyrimidines from the reaction of 3-amino-1,2,4- triazole with β-enamino-dimethyl vinyl ketones or 1,1,1-trifluoro-4-alkoxy-3-alqken-2-ones), under ultrasound irradiation.