Synthesis, crystal structure, characterization and antifungal activity of pyrazolo[1,5-a]pyrimidines derivatives

• A single-step synthesis was set up by microwave irradiation, yielding a mixture of isomers 2-(pyrazolo[1,5-a]pyrimidin-5-yl)phenols (3) and 2-(pyrazolo[1,5-a]pyrimidin -7-yl)phenols (4), and they were characterized by the spectroscopy of IR, 1H NMR, 13C NMR and HRMS.
• The crystal structure of 5-chloro-2-(2-methyl-pyrazolo[1,5-a]pyrimidin-5-yl)phenol was determined.
• Compounds 3 and 4 were evaluated the antifungal abilities against five phytopathogenic fungi.

Under microwave radiation, isomers 2-(pyrazolo[1,5-a]pyrimidin-5-yl)phenols (3) and 2-(pyrazolo[1,5-a]pyrimidin-7-yl)phenols (4) were simultaneously obtained by the condensation of chromones and 3-aminopyrazoles. These two isomers were fully characterized by IR, 1H NMR, 13C NMR and HRMS. In addition, a representative product 5-chloro-2-(2-methyl-pyrazolo[1,5-a] pyrimidin-5-yl)phenol (3e) was further conformed by the single crystal X-ray diffraction. The antifungal abilities of the obtained products 3 and 4 were evaluated against five phytopathogenic fungi (Cytospora sp., Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria solani and Fusarium solani). The results revealed that 2-(pyrazolo[1,5-a]pyrimidin-5-yl)phenol (3a) and 4-chloro-2-(2-methylpyrazolo[1,5-a]pyrimidin-7-yl)phenol (4e) exhibited good antifungal abilities against Colletotrichum gloeosporioides with the IC50 values of 24.90 and 28.28 μg/mL, respectively.

2-(pyrazolo[1,5-a]pyrimidin-5-yl)phenols (3) and 2-(pyrazolo[1,5-a]pyrimidin-7-yl) phenols (4) were simultaneously synthesized by the condensation of chromones and 3-aminopyrazoles under the microwave radiation. They were characterized by the method of IR, 1H NMR, 13C NMR and HRMS and were evaluated the antifungal abilities against five phytopathogenic fungi.Figure optionsDownload as PowerPoint slide