Design, synthesis and fungicidal activities of some novel pyrazole derivatives.

Xue-Ru Liu,Zhi-Qing Ma,Hua Wu,Jun-Tao Feng,Xing Zhang,Ze-Yu He

doi:10.3390/molecules190914036

Abstract

In order to discover new compounds with good fungicidal activities, 32 pyrazole derivatives were designed and synthesized. The structures of the target compounds were confirmed by 1H-NMR, 13C-NMR, and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS), and their fungicidal activities against Botrytis cinerea, Rhizoctonia solani Kuhn, Valsa mali Miyabe et Yamada, Thanatephorus cucumeris (Frank) Donk, Fusarium oxysporum (S-chl) f.sp. cucumerinum Owen, and Fusarium graminearum Schw were tested. The bioassay results indicated that most of the derivatives exhibited considerable antifungal activities, especially compound 26 containing a p-trifluoromethyl- phenyl moiety showed the highest activity, with EC50 values of 2.432, 2.182, 1.787, 1.638, 6.986, and 6.043 μg/mL against B. cinerea, R. solani, V. mali, T. cucumeris, F. oxysporum, and F. graminearum, respectively. Moreover, the activities of compounds such as compounds 27–32 were enhanced by introducing isothiocyanate and carboxamide moieties to the 5-position of the pyrazole ring.

Highlights

It was well accepted that agricultural diseases caused by pathogenic fungi threaten the security and efficiency of crop production [1,2,3]
Thirty-two title compounds were prepared according to the methods presented in Scheme 1, including twenty-six 1,3,4-substituted-5-aminopyrazole derivatives, two 1,3,4-substituted pyrazole amides, and four 1,3,4-substituted pyrazole isothiocyanates
Most of target compounds were synthesized in good yields of 90% or higher and were characterized by 1H-NMR, 13C-NMR and HR-MS (ESI)

Summary

Introduction

It was well accepted that agricultural diseases caused by pathogenic fungi threaten the security and efficiency of crop production [1,2,3]. In order to maintain a substantial increase in crop production and to meet humans’ growing demand for food quality and quantity, fungicides are widely used for crop protection [4]. Many commercial chemical fungicides have been challenged by the development of resistance [5,6]. There is an urgent need for novel highly active fungicides, especially those with new modes of action, to handle these problems. Compounds with pyrazole functional units exhibit antimicrobial [7], herbicidal [8], antitumor [9], insecticidal [10,11,12,13], fungicidal [14,15,16,17,18] and antiviral activities [19,20]

Methods

Findings

Discussion

Conclusion