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

Abstract 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, 1 H NMR, 13 C 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 IC 50 values of 24.90 and 28.28  μ g/mL, respectively.