Design, Synthesis and Fungicidal Activities of Some Novel Pyrazole Derivatives

Abstract

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 1 H-NMR, 13 C-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-trifluoromethylphenyl moiety showed the highest activity, with EC 50 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.

Selective Incorporation of Fluorine in Pyrazoles

“…[32] Fused-ring N-fluoroarylpyrazole systems have also been prepared and examples are shown in Scheme 2. [40] [33] Condensations of (4-fluorophenyl)hydrazine with cyclic β-oxodithioesters 13a, α-oxoketene dithioacetals 13b under basic conditions followed by desulfurization with Raney nickel to yield the regioisomeric fused-ring pyrazoles 14a and 14b, respectively, were reported by Peruncheralathan and co-workers in yields ranging from 45-96 %.…”

Design, Synthesis, and Anticancer Activity of Novel Benzothiazole Analogues

“…To a solution of compound 26 (0.37 g, 1 mmol) in DMF (10 mL) an equimolar amount of either compound 32 (0.17 g, 1 mmol) or compound 33 (0.22 g, 1 mmol) was added, and the reaction mixture was heated under reflux in the presence of TEA (two drops) for 66–70 h. The solvent was then evaporated, and the solid mass was triturated with ethanol, and the obtained solid was filtered, washed with ethanol, dried and crystallized from ethanol to afford compounds 34a and 34b , respectively.…”

Key Intermediates: A Simple and Highly Selective Synthesis of 5-<i>Amino</i>-1-<i>aryl</i>-1<i>H</i>-<i>pyrazole</i>-4-<i>carbonitriles</i> for Applications in the Crop Protection

“…HRMS were obtained on a Bruker micro QTOF-Q11 mass spectrometer equipped with an electrospray ionization (ESI). 1 H NMR (300 MHz), 13 C NMR (75 MHz). 19 F NMR (300 MHz), COSY (Correlation spectroscopy), HSQC (heteronuclear single-quantum correlation spectroscopy) and HMBC (heteronuclear multiple-bond correlation spectroscopy) experiments were recorded on a Bruker Avance 300 spectrometer in CDCl 3 using TMS as internal standard.…”

“…The above mentioned general procedure gave 3a-f in 84%, 47%, 63%, 67%, 47%, and 68% yields, respectively. Once purified, the pyrazole was characterized by NMR ( 1 H, 13 C, 19 F, COSY, HSQC and HMBC). For aryl hydrazines hydrochlorides 2b, 2f (1.2 mmol), a previous step of neutralization with Et 3 N (1.0 mmol) at 0˚C in ethanol (2 mL) was needed.…”