# Synthesis, Structure, and Antifungal Activities of 3-(Difluoromethyl)-Pyrazole-4-Carboxylic Oxime Ester Derivatives

Authors: Bin Wang; Wei-Ting Chen; Li-Jing Min; Liang Han; Na-Bo Sun; Xing-Hai Liu
Journal: Heteroatom Chemistry
 (2022)

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## Abstract

Fifteen new pyrazole-4-carboxylic oxime ester derivatives were conveniently synthesized, and their structures were confirmed by1H NMR, 13C NMR, HRMS, and X-ray diffraction. Antifungal assays indicated that some of these compounds possessed good activity against S. sclerotiorum, B. cinerea, R. solani, P. oryae, and P. piricola at 50 ppm. Structure-activity relationships (SAR) were studied by molecular docking simulation.


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## Body

## 1. Introduction

Nitrogen-linked heterocycles are an important skeleton in synthetic chemistry or natural product chemistry because of their diversity of structure and activity [1–5]. Among these nitrogen-linked heterocycles; pyrazole compounds, especially pyrazole carboxamide compounds, exhibit diverse activity, with examples possessing nematocidal [6–10], insecticidal [11, 12], antibacterial [13], IRAK4 inhibitor [14], antiproliferative [15], antimicrobial [16], immunomodulatory [17], and fungicidal activity [18–20]. Some pyrazole amide compounds have been commercialized as fungicides [21] or insecticides [22]. For example, benzovindiflupyr, a new succinate dehydrogenase inhibitor (SDH) fungicide developed by Syngenta. In these SDH fungicides, the pyrazole ring and carboxamide group are the key functional groups accounting for their activity.In our previous work, many nitrogen-linked heterocyclic compounds with diverse activity were synthesized [23–27], including many fungicidal pyrazole carboxamide derivatives. In this work, the carboxamide group was replaced by an oxime ester group (Figure 1). In this paper, a set of pyrazole oxime esters were synthesized, and their fungicidal activity was assessed. This data was used to assess the structure-activity relationship (SAR) using molecular docking.Figure 1
Design strategy of pyrazole oxime ester compounds 5a∼5o.


## 2. Materials and Methods

### 2.1. Instruments

Melting points were measured by an X-4 apparatus (Gongyi, China) and the temperature was uncorrected.1H NMR and 13C NMR spectra were tested on a Bruker AV III-500 instrument and 13C NMR spectra were tested on a Bruker AV-400 instrument in CDCl3. DART-HRMS was measured on a JEOL AccuTOF instrument. Single crystal diffraction was performed on a Bruker CCD area detector diffractometer.


### 2.2. Chemicals

All benzaldehydes (98% purity) were purchased from Duodian Chemical Co. Ltd, China. Ethyl difluoroacetate and methyl hydrazine were purchased from Taizhou Yongxiang Pharmaceutical company; triethyl orthoformate, acetic acid, ethanol, hydroxylamine hydrochloride, and dichlorosulfoxide were purchased from Mclean; sodium hydroxide was purchased from Yongda Reagent company; potassium carbonate, hydrochloric acid, and DCM were purchased from Sinopharm Chemical Reagent Co. Ltd.; TEA was purchased from Qidian Reagent company.


### 2.3. Experimental Methods

#### 2.3.1. Synthesis of Intermediate Oximes

Benzaldehyde (9.5 mmol) was added to a mixture of Na2CO3 (0.5 g, 4.7 mmol) in ethanol (10 mL) and the mixture was stirred at room temperature. After 30 min, NH2OH·HCl (0.7 g, 10.4 mmol) was added, and the reaction was monitored by TLC. The water phase was extracted with ethyl acetate (3 × 20 mL). The combined organic layers were washed with saturated brine (3 × 10 mL), dried with MgSO4, and evaporated in vacuo. The crude product was recrystallized from ethanol and used without further purification.


#### 2.3.2. Synthesis of Target Compounds5a-5o

The two key intermediates: benzaldehyde oxime and 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride were synthesized according to our previous reported work [26].A solution of intermediate benzaldehyde oxime (7.5 mmol) and NEt3 (1 mL) in dichloromethane (20 mL), 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride (7.5 mmol) was added dropwise at ice bath condition, then the mixture was stirred at 20°C. When the reaction was complete (TLC monitoring (VEA/VPE = 1/2)), the solvent was removed in vacuo, and the crude products were purified by flash chromatography to afford the title compound 5a-5o.


#### 2.3.3. (E)-Benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5a

White solid, yield 73%, m.p. 171–177°C;1H NMR (CDCl3, 500 MHz), δ:8.46 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.80–7.76 (m, 2H, Ph), 7.52–7.42 (m, 3H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.2, 156.8, 146.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 146.2, 135.3, 131.9, 129.8, 128.9, 128.5, 109.3 (t, J = 238.4 Hz, CHF2), 110.8, 39.81; HRMS (DART) for C13H11F2N3O2 m/z: calculated, 280.0892, found, 280.0897 [M+H]+.


#### 2.3.4. (E)-2-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5b

White solid, yield 72%, m.p. 120–123°C;1H NMR (CDCl3, 500 MHz), δ:8.71 (s, 1H, CH), 8.04 (d, J = 1.0 Hz, 1H, pyrazole), 7.88 (dd, J = 7.8, 1.4 Hz, 1H, Ph), 7.38 (td, J = 7.5, 1.4 Hz, 1H, Ph), 7.28–7.24 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3), 2.51 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 155.7, 146.6 (t, J = 26.3 Hz, Py-CHF2), 138.2, 135.1, 131.5, 131.0, 128.3, 128.2, 126.3, 110.8, 109.2 (t, J = 238.4 Hz, CHF2), 39.8, 19.9; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


#### 2.3.5. (E)-3-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5c

White solid, yield 71%, m.p. 119–123°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.65 (d, J = 2.1 Hz, 1H, Ph), 7.53 (d, J = 7.3 Hz, 1H, Ph), 7.34–7.26 (m, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.39 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 138.8, 135.2, 132.7, 129.7, 128.7, 128.5, 126.0, 110.8, 109.3 (t, J = 238.4 Hz, CHF2), 39.8, 21.1; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


#### 2.3.6. (E)-4-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5d

White solid, yield 71%, m.p. 147–150°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.02 (s, 1H, Pyrazole), 7.67 (d, J = 8.1 Hz, 2H, Ph), 7.24 (d, J = 8.0 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.40 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.3, 156.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 142.5, 135.3, 129.6 (2C, Ph), 128.4 (2C, Ph), 126.9, 110.9, 109.3 (t, J = 238.1 Hz, CHF2), 39.8, 21.6; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


#### 2.3.7. (E)-2-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5e

Light yellow solid, yield 70%, m.p. 116–120°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.02–8.01 (m, 2H, pyrazole, Ph), 7.46 (ddd, J = 8.8, 7.5, 1.8 Hz, 1H, Ph), 7.16 (t, J = 53.8 Hz, 1H, CHF2), 7.00 (t, J = 7.5 Hz, 1H, Ph), 6.93 (dd, J = 8.5, 0.9 Hz, 1H, Ph), 4.00 (s, 3H, CH3), 3.89 (s, 3H, CH3O), 1.26 (d, J = 7.0 Hz, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.3, 158.4, 152.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.2, 127.4, 120.7, 118.1, 111.0, 110.8, 109.1 (t, J = 238.4 Hz, CHF2), 55.5, 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


#### 2.3.8. (E)-4-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5f

Light yellow solid, yield 70%, m.p. 131–138°C;1H NMR (CDCl3, 500 MHz), δ:8.40 (s, 1H, CH), 8.02 (s, 1H, pyrazole), 7.73 (d, J = 8.8 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 6.96 (d, J = 8.8 Hz, 2H, Ph), 4.00 (s, 3H, CH3), 3.86 (s, 3H, CH3O); 13C NMR (CDCl3, 101 MHz), δ: 162.5, 159.4, 156.3, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 132.3, 130.2 (2C, Ph), 122.2, 114.4 (2C, Ph), 109.3 (t, J = 237.1 Hz, CHF2), 55.4, 39.4; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


#### 2.3.9. (E)-3,4,5-Trimethoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5g

White solid, yield 68%, m.p. 153–157°C;1H NMR (CDCl3, 500 MHz), δ:8.37 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.10 (t, J = 53.8 Hz, 1H, CHF2), 6.99 (s, 2H, Ph), 4.00 (s, 3H, CH3), 3.91 (d, J = 3.4 Hz, 9H, CH3O); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 153.4, 146.3 (t, J = 26.3 Hz, Py-CHF2), 141.1, 135.3, 125.0, 110.7, 109.3 (t, J = 237.0 Hz, CHF2), 105.5, 60.7, 56.2 (2C, OCH3), 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 370.1209, found, 370.1213 [M+H]+.


#### 2.3.10. (E)-2-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5h

Light yellow solid, yield 70%, m.p. 124–130°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.11 (dd, J = 7.6, 2.0 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.63 (dd, J = 7.8, 1.5 Hz, 1H, Ph), 7.39–7.33 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.8, 146.6 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.1, 132.9, 129.3, 128.6, 127.7, 124.8, 110.3, 109.1 (t, J = 238.4 Hz, CHF2), 39.7. HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9972 [M+H]+.


#### 2.3.11. (E)-4-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5i

Light yellow solid, yield 69%, m.p.180–183°C;1H NMR (CDCl3, 500 MHz), δ:8.41 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.66 (d, J = 8.5 Hz, 2H, Ph), 7.60 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 125 MHz) δ: 155.7, 153.7, 145.9 (t, J = 25.6 Hz, Py-CHF2), 135.5, 132.3 (2C, Ph), 129.8 (2C, Ph), 128.8, 126.5, 109.3 (t, J = 237.3 Hz, CHF2), 49.1, 40.2; HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9977 [M+H]+.


#### 2.3.12. (E)-2-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5j

White solid, yield 73%, m.p. 146–149°C;1H NMR (CDCl3, 500 MHz), δ:9.09 (s, 1H, CH), 8.19 (ddd, J = 17.1, 8.0, 1.4 Hz, 2H, Ph), 8.06 (s, 1H, pyrazole), 7.76 (td, J = 7.6, 1.3 Hz, 1H, Ph), 7.70 (td, J = 7.8, 1.5 Hz, 1H, Ph), 7.13 (t, J = 53.7 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.8, 153.6, 148.0, 146.9 (t, J = 24.8 Hz, Py-CHF2), 135.3, 134.1, 132.0, 130.1, 125.5, 125.1, 110.2, 109.1 (t, J = 237.3 Hz, CHF2), 39.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


#### 2.3.13. (E)-3-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5k

Light yellow solid, yield 71%, m.p.172–176°C;1H NMR (CDCl3, 500 MHz), δ:8.59 (t, J = 1.9 Hz, 1H, Ph), 8.56 (s, 1H, CH), 8.35 (ddd, J = 8.2, 2.3, 1.1 Hz, 1H, Ph), 8.21 (dt, J = 7.9, 1.4 Hz, 1H, Ph), 8.06 (s, 1H, pyrazole), 7.67 (t, J = 8.0 Hz, 1H, Ph), 7.07 (t, J = 53.8 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 157.7, 153.4, 145.8, 145.5 (t, J = 27.3 Hz, Py-CHF2), 145.3, 134.6, 132.5, 130.8, 129.1, 125.2, 122.5, 108.4 (t, J = 238.4 Hz, CHF2), 38.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


#### 2.3.14. (E)-4-Fluorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5l

Light yellow solid, yield 71%, m.p. 144–147°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.79 (dd, J = 8.8, 5.3 Hz, 2H, Ph), 7.14 (t, J = 8.6 Hz, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ 163.5, 159.1, 155.50, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 130.5 (d, J = 8.1 Hz, 2C, Ph), 126.1 (d, J = 3.0 Hz, Ph), 116.3 (d, J = 11.1 Hz, 2C, Ph), 110.7, 109.3 (t, J = 238.4 Hz, CHF2), 39.8; HRMS (DART) for C13H10F3N3O2 m/z: calculated, 298.0798, found, 298.0803 [M+H]+.


#### 2.3.15. (E)-4-(Trifluoromethyl)benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5m

White solid, yield 70%, m.p. 129–133°C;1H NMR (CDCl3, 500 MHz), δ:8.51 (s, 1H, CH), 8.05 (s, 1H, pyrazole), 7.90 (d, J = 8.1 Hz, 2H, Ph), 7.70 (d, J = 8.2 Hz, 2H, Ph), 7.08 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.3, 146.3 (t, J = 25.3 Hz, Py-CHF2), 135.8, 135.6 (2C, Ph), 133.3, 128.7 (2C, Ph), 125.9 (q, J = 3.8 Hz, Ph), 124.9 (q, J = 272.8 Hz, CF3), 110.0, 109.3 (t, J = 236.9 Hz, CHF2), 39.8; HRMS (DART) for C14H10F5N3O2 m/z: calculated, 348.0766, found, 348.0771 [M+H]+.


#### 2.3.16. (E)-4-Chlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5n

White solid, yield 69%, m.p.163–169°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.73 (d, J = 8.5 Hz, 2H, Ph), 7.44 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.0, 155.5, 146.5 (t, J = 24.3 Hz, Py-CHF2), 138.0, 135.4, 132.3, 129.6 (2C, Ph), 129.3 (2C, Ph), 128.3, 109.3 (t, J = 237.0 Hz, CHF2), 39.9; HRMS (DART) for C13H1035ClF2N3O2 m/z: calculated, 314.0502, found, 314.0508 [M+H]+; for C13H1037ClF2N3O2 m/z: calculated, 316.0502, found, 316.0508 [M+H]+.


#### 2.3.17. (E)-2,4-Dichlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5o

White solid, yield 67%, m.p. 173–176°C;1H NMR (CDCl3, 500 MHz), δ:8.83 (s, 1H, CH), 8.10 (d, J = 8.5 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.47 (d, J = 2.1 Hz, 1H, Ph), 7.33 (ddd, J = 8.5, 2.0, 0.7 Hz, 1H, Ph), 7.11 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 152.7, 146.8 (t, J = 26.3 Hz, Py-CHF2), 138.4, 135.7, 135.3, 129.9, 129.2, 127.9, 126.4, 110.4, 109.2 (t, J = 238.4 Hz, CHF2), 39.9; HRMS (DART) for C13H935Cl2F2N3O2 m/z: calculated, 348.0113, found, 348.0118 [M+H]+; for C13H937Cl2F2N3O2 m/z: calculated, 350.0113, found, 350.0118 [M+H]+.


### 2.4. Structure Determination

One colorless crystal was cultivated in EtOH by self-volatilization with dimensions of 0.28 mm × 0.22 mm × 0.14 mm for X-ray on a Bruker CCD area detector diffractometer equipped with a graphite-monochromatic MoKα radiation (λ = 0.71073 Å). The structure of compound 5d was solved using direct methods by ShelXS [28] structure solution program and refined with the ShelXL [29] refinement package using least squares minimization in Olex2 software [30]. The detailed crystal data are listed in Table 1.Table 1
Crystal data of compound5d.
Name5dEmpirical formulaC14H13F2N3O2Formula weight293.27Temperature/K296 (2)Crystal systemMonoclinicCrystal size/mm30.36 × 0.34 × 0.32Space groupC2/ca/Å16.6161 (11)b/Å15.7963 (9)c/Å12.9160 (8)α/°90β/°124.693 (2)γ/°90Volume/Å2787.4 (3)Z8ρcalcg/cm31.398μ/mm−10.114F (000)1216.0RadiationMoKα (λ = 0.71073)2Θ range for data collection/°5.964 to 54.944Index ranges-21 ≤h ≤ 21, -20 ≤ k ≤ 20, -16 ≤ l ≤ 16Reflections collected32252Independent reflections3192 [Rint = 0.0505, Rsigma = 0.0285]Data/restraints/parameters3192/0/192Goodness-of-fit on F21.046FinalR indexes (I ≥ 2σ (I))R1 = 0.0491, wR2 = 0.1243FinalR indexes (all data)R1 = 0.0763, wR2 = 0.1394Largest diff. peak/hole/e Å−30.23/-0.24


### 2.5. Fungicidal Activity

Fungicidal activities of pyrazole-4-carboxylic oxime ester derivatives5a∼5o were tested according to reported work [31, 32]. The antifungal activities of compounds 5a-5o and fluxapyroxad were tested in vitro against Gibberella zeae (GZ), Fusarium oxysporum (FO), Phytophthora infestans (PI), Phytophthora capsici (PC), Rhizoctonia solani (RS), Sclerotinia sclerotiorum (SS), Alternaria solani (AS), Physalospora piricola (PP), Cercospora arachidicola (CA), and Botrytis cinerea (BC). The relative percent inhibition (%) has been determined using the mycelium growth rate method. The inhibition of the test compounds compared to the blank assay was calculated via the following equation:(1)inhibition%=CK−CICK×100%,where CK is the average diameter of mycelia in the blank test and CI is the average diameter of mycelia in the presence of those compounds. All experiments were replicated three times.


## 2.1. Instruments

Melting points were measured by an X-4 apparatus (Gongyi, China) and the temperature was uncorrected.1H NMR and 13C NMR spectra were tested on a Bruker AV III-500 instrument and 13C NMR spectra were tested on a Bruker AV-400 instrument in CDCl3. DART-HRMS was measured on a JEOL AccuTOF instrument. Single crystal diffraction was performed on a Bruker CCD area detector diffractometer.


## 2.2. Chemicals

All benzaldehydes (98% purity) were purchased from Duodian Chemical Co. Ltd, China. Ethyl difluoroacetate and methyl hydrazine were purchased from Taizhou Yongxiang Pharmaceutical company; triethyl orthoformate, acetic acid, ethanol, hydroxylamine hydrochloride, and dichlorosulfoxide were purchased from Mclean; sodium hydroxide was purchased from Yongda Reagent company; potassium carbonate, hydrochloric acid, and DCM were purchased from Sinopharm Chemical Reagent Co. Ltd.; TEA was purchased from Qidian Reagent company.


## 2.3. Experimental Methods

### 2.3.1. Synthesis of Intermediate Oximes

Benzaldehyde (9.5 mmol) was added to a mixture of Na2CO3 (0.5 g, 4.7 mmol) in ethanol (10 mL) and the mixture was stirred at room temperature. After 30 min, NH2OH·HCl (0.7 g, 10.4 mmol) was added, and the reaction was monitored by TLC. The water phase was extracted with ethyl acetate (3 × 20 mL). The combined organic layers were washed with saturated brine (3 × 10 mL), dried with MgSO4, and evaporated in vacuo. The crude product was recrystallized from ethanol and used without further purification.


### 2.3.2. Synthesis of Target Compounds5a-5o

The two key intermediates: benzaldehyde oxime and 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride were synthesized according to our previous reported work [26].A solution of intermediate benzaldehyde oxime (7.5 mmol) and NEt3 (1 mL) in dichloromethane (20 mL), 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride (7.5 mmol) was added dropwise at ice bath condition, then the mixture was stirred at 20°C. When the reaction was complete (TLC monitoring (VEA/VPE = 1/2)), the solvent was removed in vacuo, and the crude products were purified by flash chromatography to afford the title compound 5a-5o.


### 2.3.3. (E)-Benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5a

White solid, yield 73%, m.p. 171–177°C;1H NMR (CDCl3, 500 MHz), δ:8.46 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.80–7.76 (m, 2H, Ph), 7.52–7.42 (m, 3H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.2, 156.8, 146.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 146.2, 135.3, 131.9, 129.8, 128.9, 128.5, 109.3 (t, J = 238.4 Hz, CHF2), 110.8, 39.81; HRMS (DART) for C13H11F2N3O2 m/z: calculated, 280.0892, found, 280.0897 [M+H]+.


### 2.3.4. (E)-2-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5b

White solid, yield 72%, m.p. 120–123°C;1H NMR (CDCl3, 500 MHz), δ:8.71 (s, 1H, CH), 8.04 (d, J = 1.0 Hz, 1H, pyrazole), 7.88 (dd, J = 7.8, 1.4 Hz, 1H, Ph), 7.38 (td, J = 7.5, 1.4 Hz, 1H, Ph), 7.28–7.24 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3), 2.51 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 155.7, 146.6 (t, J = 26.3 Hz, Py-CHF2), 138.2, 135.1, 131.5, 131.0, 128.3, 128.2, 126.3, 110.8, 109.2 (t, J = 238.4 Hz, CHF2), 39.8, 19.9; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


### 2.3.5. (E)-3-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5c

White solid, yield 71%, m.p. 119–123°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.65 (d, J = 2.1 Hz, 1H, Ph), 7.53 (d, J = 7.3 Hz, 1H, Ph), 7.34–7.26 (m, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.39 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 138.8, 135.2, 132.7, 129.7, 128.7, 128.5, 126.0, 110.8, 109.3 (t, J = 238.4 Hz, CHF2), 39.8, 21.1; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


### 2.3.6. (E)-4-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5d

White solid, yield 71%, m.p. 147–150°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.02 (s, 1H, Pyrazole), 7.67 (d, J = 8.1 Hz, 2H, Ph), 7.24 (d, J = 8.0 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.40 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.3, 156.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 142.5, 135.3, 129.6 (2C, Ph), 128.4 (2C, Ph), 126.9, 110.9, 109.3 (t, J = 238.1 Hz, CHF2), 39.8, 21.6; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


### 2.3.7. (E)-2-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5e

Light yellow solid, yield 70%, m.p. 116–120°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.02–8.01 (m, 2H, pyrazole, Ph), 7.46 (ddd, J = 8.8, 7.5, 1.8 Hz, 1H, Ph), 7.16 (t, J = 53.8 Hz, 1H, CHF2), 7.00 (t, J = 7.5 Hz, 1H, Ph), 6.93 (dd, J = 8.5, 0.9 Hz, 1H, Ph), 4.00 (s, 3H, CH3), 3.89 (s, 3H, CH3O), 1.26 (d, J = 7.0 Hz, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.3, 158.4, 152.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.2, 127.4, 120.7, 118.1, 111.0, 110.8, 109.1 (t, J = 238.4 Hz, CHF2), 55.5, 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


### 2.3.8. (E)-4-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5f

Light yellow solid, yield 70%, m.p. 131–138°C;1H NMR (CDCl3, 500 MHz), δ:8.40 (s, 1H, CH), 8.02 (s, 1H, pyrazole), 7.73 (d, J = 8.8 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 6.96 (d, J = 8.8 Hz, 2H, Ph), 4.00 (s, 3H, CH3), 3.86 (s, 3H, CH3O); 13C NMR (CDCl3, 101 MHz), δ: 162.5, 159.4, 156.3, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 132.3, 130.2 (2C, Ph), 122.2, 114.4 (2C, Ph), 109.3 (t, J = 237.1 Hz, CHF2), 55.4, 39.4; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


### 2.3.9. (E)-3,4,5-Trimethoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5g

White solid, yield 68%, m.p. 153–157°C;1H NMR (CDCl3, 500 MHz), δ:8.37 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.10 (t, J = 53.8 Hz, 1H, CHF2), 6.99 (s, 2H, Ph), 4.00 (s, 3H, CH3), 3.91 (d, J = 3.4 Hz, 9H, CH3O); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 153.4, 146.3 (t, J = 26.3 Hz, Py-CHF2), 141.1, 135.3, 125.0, 110.7, 109.3 (t, J = 237.0 Hz, CHF2), 105.5, 60.7, 56.2 (2C, OCH3), 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 370.1209, found, 370.1213 [M+H]+.


### 2.3.10. (E)-2-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5h

Light yellow solid, yield 70%, m.p. 124–130°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.11 (dd, J = 7.6, 2.0 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.63 (dd, J = 7.8, 1.5 Hz, 1H, Ph), 7.39–7.33 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.8, 146.6 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.1, 132.9, 129.3, 128.6, 127.7, 124.8, 110.3, 109.1 (t, J = 238.4 Hz, CHF2), 39.7. HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9972 [M+H]+.


### 2.3.11. (E)-4-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5i

Light yellow solid, yield 69%, m.p.180–183°C;1H NMR (CDCl3, 500 MHz), δ:8.41 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.66 (d, J = 8.5 Hz, 2H, Ph), 7.60 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 125 MHz) δ: 155.7, 153.7, 145.9 (t, J = 25.6 Hz, Py-CHF2), 135.5, 132.3 (2C, Ph), 129.8 (2C, Ph), 128.8, 126.5, 109.3 (t, J = 237.3 Hz, CHF2), 49.1, 40.2; HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9977 [M+H]+.


### 2.3.12. (E)-2-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5j

White solid, yield 73%, m.p. 146–149°C;1H NMR (CDCl3, 500 MHz), δ:9.09 (s, 1H, CH), 8.19 (ddd, J = 17.1, 8.0, 1.4 Hz, 2H, Ph), 8.06 (s, 1H, pyrazole), 7.76 (td, J = 7.6, 1.3 Hz, 1H, Ph), 7.70 (td, J = 7.8, 1.5 Hz, 1H, Ph), 7.13 (t, J = 53.7 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.8, 153.6, 148.0, 146.9 (t, J = 24.8 Hz, Py-CHF2), 135.3, 134.1, 132.0, 130.1, 125.5, 125.1, 110.2, 109.1 (t, J = 237.3 Hz, CHF2), 39.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


### 2.3.13. (E)-3-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5k

Light yellow solid, yield 71%, m.p.172–176°C;1H NMR (CDCl3, 500 MHz), δ:8.59 (t, J = 1.9 Hz, 1H, Ph), 8.56 (s, 1H, CH), 8.35 (ddd, J = 8.2, 2.3, 1.1 Hz, 1H, Ph), 8.21 (dt, J = 7.9, 1.4 Hz, 1H, Ph), 8.06 (s, 1H, pyrazole), 7.67 (t, J = 8.0 Hz, 1H, Ph), 7.07 (t, J = 53.8 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 157.7, 153.4, 145.8, 145.5 (t, J = 27.3 Hz, Py-CHF2), 145.3, 134.6, 132.5, 130.8, 129.1, 125.2, 122.5, 108.4 (t, J = 238.4 Hz, CHF2), 38.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


### 2.3.14. (E)-4-Fluorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5l

Light yellow solid, yield 71%, m.p. 144–147°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.79 (dd, J = 8.8, 5.3 Hz, 2H, Ph), 7.14 (t, J = 8.6 Hz, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ 163.5, 159.1, 155.50, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 130.5 (d, J = 8.1 Hz, 2C, Ph), 126.1 (d, J = 3.0 Hz, Ph), 116.3 (d, J = 11.1 Hz, 2C, Ph), 110.7, 109.3 (t, J = 238.4 Hz, CHF2), 39.8; HRMS (DART) for C13H10F3N3O2 m/z: calculated, 298.0798, found, 298.0803 [M+H]+.


### 2.3.15. (E)-4-(Trifluoromethyl)benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5m

White solid, yield 70%, m.p. 129–133°C;1H NMR (CDCl3, 500 MHz), δ:8.51 (s, 1H, CH), 8.05 (s, 1H, pyrazole), 7.90 (d, J = 8.1 Hz, 2H, Ph), 7.70 (d, J = 8.2 Hz, 2H, Ph), 7.08 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.3, 146.3 (t, J = 25.3 Hz, Py-CHF2), 135.8, 135.6 (2C, Ph), 133.3, 128.7 (2C, Ph), 125.9 (q, J = 3.8 Hz, Ph), 124.9 (q, J = 272.8 Hz, CF3), 110.0, 109.3 (t, J = 236.9 Hz, CHF2), 39.8; HRMS (DART) for C14H10F5N3O2 m/z: calculated, 348.0766, found, 348.0771 [M+H]+.


### 2.3.16. (E)-4-Chlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5n

White solid, yield 69%, m.p.163–169°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.73 (d, J = 8.5 Hz, 2H, Ph), 7.44 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.0, 155.5, 146.5 (t, J = 24.3 Hz, Py-CHF2), 138.0, 135.4, 132.3, 129.6 (2C, Ph), 129.3 (2C, Ph), 128.3, 109.3 (t, J = 237.0 Hz, CHF2), 39.9; HRMS (DART) for C13H1035ClF2N3O2 m/z: calculated, 314.0502, found, 314.0508 [M+H]+; for C13H1037ClF2N3O2 m/z: calculated, 316.0502, found, 316.0508 [M+H]+.


### 2.3.17. (E)-2,4-Dichlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5o

White solid, yield 67%, m.p. 173–176°C;1H NMR (CDCl3, 500 MHz), δ:8.83 (s, 1H, CH), 8.10 (d, J = 8.5 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.47 (d, J = 2.1 Hz, 1H, Ph), 7.33 (ddd, J = 8.5, 2.0, 0.7 Hz, 1H, Ph), 7.11 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 152.7, 146.8 (t, J = 26.3 Hz, Py-CHF2), 138.4, 135.7, 135.3, 129.9, 129.2, 127.9, 126.4, 110.4, 109.2 (t, J = 238.4 Hz, CHF2), 39.9; HRMS (DART) for C13H935Cl2F2N3O2 m/z: calculated, 348.0113, found, 348.0118 [M+H]+; for C13H937Cl2F2N3O2 m/z: calculated, 350.0113, found, 350.0118 [M+H]+.


## 2.3.1. Synthesis of Intermediate Oximes

Benzaldehyde (9.5 mmol) was added to a mixture of Na2CO3 (0.5 g, 4.7 mmol) in ethanol (10 mL) and the mixture was stirred at room temperature. After 30 min, NH2OH·HCl (0.7 g, 10.4 mmol) was added, and the reaction was monitored by TLC. The water phase was extracted with ethyl acetate (3 × 20 mL). The combined organic layers were washed with saturated brine (3 × 10 mL), dried with MgSO4, and evaporated in vacuo. The crude product was recrystallized from ethanol and used without further purification.


## 2.3.2. Synthesis of Target Compounds5a-5o

The two key intermediates: benzaldehyde oxime and 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride were synthesized according to our previous reported work [26].A solution of intermediate benzaldehyde oxime (7.5 mmol) and NEt3 (1 mL) in dichloromethane (20 mL), 3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbonyl chloride (7.5 mmol) was added dropwise at ice bath condition, then the mixture was stirred at 20°C. When the reaction was complete (TLC monitoring (VEA/VPE = 1/2)), the solvent was removed in vacuo, and the crude products were purified by flash chromatography to afford the title compound 5a-5o.


## 2.3.3. (E)-Benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5a

White solid, yield 73%, m.p. 171–177°C;1H NMR (CDCl3, 500 MHz), δ:8.46 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.80–7.76 (m, 2H, Ph), 7.52–7.42 (m, 3H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.2, 156.8, 146.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 146.2, 135.3, 131.9, 129.8, 128.9, 128.5, 109.3 (t, J = 238.4 Hz, CHF2), 110.8, 39.81; HRMS (DART) for C13H11F2N3O2 m/z: calculated, 280.0892, found, 280.0897 [M+H]+.


## 2.3.4. (E)-2-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5b

White solid, yield 72%, m.p. 120–123°C;1H NMR (CDCl3, 500 MHz), δ:8.71 (s, 1H, CH), 8.04 (d, J = 1.0 Hz, 1H, pyrazole), 7.88 (dd, J = 7.8, 1.4 Hz, 1H, Ph), 7.38 (td, J = 7.5, 1.4 Hz, 1H, Ph), 7.28–7.24 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3), 2.51 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 155.7, 146.6 (t, J = 26.3 Hz, Py-CHF2), 138.2, 135.1, 131.5, 131.0, 128.3, 128.2, 126.3, 110.8, 109.2 (t, J = 238.4 Hz, CHF2), 39.8, 19.9; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


## 2.3.5. (E)-3-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5c

White solid, yield 71%, m.p. 119–123°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.65 (d, J = 2.1 Hz, 1H, Ph), 7.53 (d, J = 7.3 Hz, 1H, Ph), 7.34–7.26 (m, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.39 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 146.5 (t, J = 26.3 Hz, Py-CHF2), 138.8, 135.2, 132.7, 129.7, 128.7, 128.5, 126.0, 110.8, 109.3 (t, J = 238.4 Hz, CHF2), 39.8, 21.1; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


## 2.3.6. (E)-4-Methylbenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5d

White solid, yield 71%, m.p. 147–150°C;1H NMR (CDCl3, 500 MHz), δ:8.42 (s, 1H, CH), 8.02 (s, 1H, Pyrazole), 7.67 (d, J = 8.1 Hz, 2H, Ph), 7.24 (d, J = 8.0 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3), 2.40 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.3, 156.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 142.5, 135.3, 129.6 (2C, Ph), 128.4 (2C, Ph), 126.9, 110.9, 109.3 (t, J = 238.1 Hz, CHF2), 39.8, 21.6; HRMS (DART) for C14H13F2N3O2 m/z: calculated, 294.1049, found, 294.1054 [M+H]+.


## 2.3.7. (E)-2-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5e

Light yellow solid, yield 70%, m.p. 116–120°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.02–8.01 (m, 2H, pyrazole, Ph), 7.46 (ddd, J = 8.8, 7.5, 1.8 Hz, 1H, Ph), 7.16 (t, J = 53.8 Hz, 1H, CHF2), 7.00 (t, J = 7.5 Hz, 1H, Ph), 6.93 (dd, J = 8.5, 0.9 Hz, 1H, Ph), 4.00 (s, 3H, CH3), 3.89 (s, 3H, CH3O), 1.26 (d, J = 7.0 Hz, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 159.3, 158.4, 152.7, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.2, 127.4, 120.7, 118.1, 111.0, 110.8, 109.1 (t, J = 238.4 Hz, CHF2), 55.5, 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


## 2.3.8. (E)-4-Methoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5f

Light yellow solid, yield 70%, m.p. 131–138°C;1H NMR (CDCl3, 500 MHz), δ:8.40 (s, 1H, CH), 8.02 (s, 1H, pyrazole), 7.73 (d, J = 8.8 Hz, 2H, Ph), 7.12 (t, J = 53.8 Hz, 1H, CHF2), 6.96 (d, J = 8.8 Hz, 2H, Ph), 4.00 (s, 3H, CH3), 3.86 (s, 3H, CH3O); 13C NMR (CDCl3, 101 MHz), δ: 162.5, 159.4, 156.3, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 132.3, 130.2 (2C, Ph), 122.2, 114.4 (2C, Ph), 109.3 (t, J = 237.1 Hz, CHF2), 55.4, 39.4; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 310.0998, found, 310.1003 [M+H]+.


## 2.3.9. (E)-3,4,5-Trimethoxybenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5g

White solid, yield 68%, m.p. 153–157°C;1H NMR (CDCl3, 500 MHz), δ:8.37 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.10 (t, J = 53.8 Hz, 1H, CHF2), 6.99 (s, 2H, Ph), 4.00 (s, 3H, CH3), 3.91 (d, J = 3.4 Hz, 9H, CH3O); 13C NMR (101 MHz, CDCl3) δ:159.2, 156.7, 153.4, 146.3 (t, J = 26.3 Hz, Py-CHF2), 141.1, 135.3, 125.0, 110.7, 109.3 (t, J = 237.0 Hz, CHF2), 105.5, 60.7, 56.2 (2C, OCH3), 39.7; HRMS (DART) for C14H13F2N3O3 m/z: calculated, 370.1209, found, 370.1213 [M+H]+.


## 2.3.10. (E)-2-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5h

Light yellow solid, yield 70%, m.p. 124–130°C;1H NMR (CDCl3, 500 MHz), δ:8.86 (s, 1H, CH), 8.11 (dd, J = 7.6, 2.0 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.63 (dd, J = 7.8, 1.5 Hz, 1H, Ph), 7.39–7.33 (m, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.8, 146.6 (t, J = 26.3 Hz, Py-CHF2), 135.1, 133.1, 132.9, 129.3, 128.6, 127.7, 124.8, 110.3, 109.1 (t, J = 238.4 Hz, CHF2), 39.7. HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9972 [M+H]+.


## 2.3.11. (E)-4-Bromobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5i

Light yellow solid, yield 69%, m.p.180–183°C;1H NMR (CDCl3, 500 MHz), δ:8.41 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.66 (d, J = 8.5 Hz, 2H, Ph), 7.60 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 125 MHz) δ: 155.7, 153.7, 145.9 (t, J = 25.6 Hz, Py-CHF2), 135.5, 132.3 (2C, Ph), 129.8 (2C, Ph), 128.8, 126.5, 109.3 (t, J = 237.3 Hz, CHF2), 49.1, 40.2; HRMS (DART) for C13H1079BrF2N3O2 m/z: calculated, 357.9997, found, 358.0003 [M+H]+; for C13H1081BrF2N3O2 m/z: calculated, 359.9977, found, 359.9977 [M+H]+.


## 2.3.12. (E)-2-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5j

White solid, yield 73%, m.p. 146–149°C;1H NMR (CDCl3, 500 MHz), δ:9.09 (s, 1H, CH), 8.19 (ddd, J = 17.1, 8.0, 1.4 Hz, 2H, Ph), 8.06 (s, 1H, pyrazole), 7.76 (td, J = 7.6, 1.3 Hz, 1H, Ph), 7.70 (td, J = 7.8, 1.5 Hz, 1H, Ph), 7.13 (t, J = 53.7 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.8, 153.6, 148.0, 146.9 (t, J = 24.8 Hz, Py-CHF2), 135.3, 134.1, 132.0, 130.1, 125.5, 125.1, 110.2, 109.1 (t, J = 237.3 Hz, CHF2), 39.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


## 2.3.13. (E)-3-Nitrobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5k

Light yellow solid, yield 71%, m.p.172–176°C;1H NMR (CDCl3, 500 MHz), δ:8.59 (t, J = 1.9 Hz, 1H, Ph), 8.56 (s, 1H, CH), 8.35 (ddd, J = 8.2, 2.3, 1.1 Hz, 1H, Ph), 8.21 (dt, J = 7.9, 1.4 Hz, 1H, Ph), 8.06 (s, 1H, pyrazole), 7.67 (t, J = 8.0 Hz, 1H, Ph), 7.07 (t, J = 53.8 Hz, 1H, CHF2), 4.02 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ: 157.7, 153.4, 145.8, 145.5 (t, J = 27.3 Hz, Py-CHF2), 145.3, 134.6, 132.5, 130.8, 129.1, 125.2, 122.5, 108.4 (t, J = 238.4 Hz, CHF2), 38.9; HRMS (DART) for C13H10F2N4O4 m/z: calculated, 325.0743, found, 325.0748 [M+H]+.


## 2.3.14. (E)-4-Fluorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5l

Light yellow solid, yield 71%, m.p. 144–147°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.79 (dd, J = 8.8, 5.3 Hz, 2H, Ph), 7.14 (t, J = 8.6 Hz, 2H, Ph), 7.14 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ 163.5, 159.1, 155.50, 146.4 (t, J = 26.3 Hz, Py-CHF2), 135.3, 130.5 (d, J = 8.1 Hz, 2C, Ph), 126.1 (d, J = 3.0 Hz, Ph), 116.3 (d, J = 11.1 Hz, 2C, Ph), 110.7, 109.3 (t, J = 238.4 Hz, CHF2), 39.8; HRMS (DART) for C13H10F3N3O2 m/z: calculated, 298.0798, found, 298.0803 [M+H]+.


## 2.3.15. (E)-4-(Trifluoromethyl)benzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5m

White solid, yield 70%, m.p. 129–133°C;1H NMR (CDCl3, 500 MHz), δ:8.51 (s, 1H, CH), 8.05 (s, 1H, pyrazole), 7.90 (d, J = 8.1 Hz, 2H, Ph), 7.70 (d, J = 8.2 Hz, 2H, Ph), 7.08 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 155.3, 146.3 (t, J = 25.3 Hz, Py-CHF2), 135.8, 135.6 (2C, Ph), 133.3, 128.7 (2C, Ph), 125.9 (q, J = 3.8 Hz, Ph), 124.9 (q, J = 272.8 Hz, CF3), 110.0, 109.3 (t, J = 236.9 Hz, CHF2), 39.8; HRMS (DART) for C14H10F5N3O2 m/z: calculated, 348.0766, found, 348.0771 [M+H]+.


## 2.3.16. (E)-4-Chlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5n

White solid, yield 69%, m.p.163–169°C;1H NMR (CDCl3, 500 MHz), δ:8.43 (s, 1H, CH), 8.03 (s, 1H, pyrazole), 7.73 (d, J = 8.5 Hz, 2H, Ph), 7.44 (d, J = 8.5 Hz, 2H, Ph), 7.09 (t, J = 53.8 Hz, 1H, CHF2), 4.00 (s, 3H, CH3); 13C NMR (CDCl3, 101 MHz), δ: 159.0, 155.5, 146.5 (t, J = 24.3 Hz, Py-CHF2), 138.0, 135.4, 132.3, 129.6 (2C, Ph), 129.3 (2C, Ph), 128.3, 109.3 (t, J = 237.0 Hz, CHF2), 39.9; HRMS (DART) for C13H1035ClF2N3O2 m/z: calculated, 314.0502, found, 314.0508 [M+H]+; for C13H1037ClF2N3O2 m/z: calculated, 316.0502, found, 316.0508 [M+H]+.


## 2.3.17. (E)-2,4-Dichlorobenzaldehyde O-(3-(Difluoromethyl)-1-methyl-1h-pyrazole-4-carbonyl) Oxime5o

White solid, yield 67%, m.p. 173–176°C;1H NMR (CDCl3, 500 MHz), δ:8.83 (s, 1H, CH), 8.10 (d, J = 8.5 Hz, 1H, Ph), 8.05 (s, 1H, pyrazole), 7.47 (d, J = 2.1 Hz, 1H, Ph), 7.33 (ddd, J = 8.5, 2.0, 0.7 Hz, 1H, Ph), 7.11 (t, J = 53.8 Hz, 1H, CHF2), 4.01 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ:158.9, 152.7, 146.8 (t, J = 26.3 Hz, Py-CHF2), 138.4, 135.7, 135.3, 129.9, 129.2, 127.9, 126.4, 110.4, 109.2 (t, J = 238.4 Hz, CHF2), 39.9; HRMS (DART) for C13H935Cl2F2N3O2 m/z: calculated, 348.0113, found, 348.0118 [M+H]+; for C13H937Cl2F2N3O2 m/z: calculated, 350.0113, found, 350.0118 [M+H]+.


## 2.4. Structure Determination

One colorless crystal was cultivated in EtOH by self-volatilization with dimensions of 0.28 mm × 0.22 mm × 0.14 mm for X-ray on a Bruker CCD area detector diffractometer equipped with a graphite-monochromatic MoKα radiation (λ = 0.71073 Å). The structure of compound 5d was solved using direct methods by ShelXS [28] structure solution program and refined with the ShelXL [29] refinement package using least squares minimization in Olex2 software [30]. The detailed crystal data are listed in Table 1.Table 1
Crystal data of compound5d.
Name5dEmpirical formulaC14H13F2N3O2Formula weight293.27Temperature/K296 (2)Crystal systemMonoclinicCrystal size/mm30.36 × 0.34 × 0.32Space groupC2/ca/Å16.6161 (11)b/Å15.7963 (9)c/Å12.9160 (8)α/°90β/°124.693 (2)γ/°90Volume/Å2787.4 (3)Z8ρcalcg/cm31.398μ/mm−10.114F (000)1216.0RadiationMoKα (λ = 0.71073)2Θ range for data collection/°5.964 to 54.944Index ranges-21 ≤h ≤ 21, -20 ≤ k ≤ 20, -16 ≤ l ≤ 16Reflections collected32252Independent reflections3192 [Rint = 0.0505, Rsigma = 0.0285]Data/restraints/parameters3192/0/192Goodness-of-fit on F21.046FinalR indexes (I ≥ 2σ (I))R1 = 0.0491, wR2 = 0.1243FinalR indexes (all data)R1 = 0.0763, wR2 = 0.1394Largest diff. peak/hole/e Å−30.23/-0.24


## 2.5. Fungicidal Activity

Fungicidal activities of pyrazole-4-carboxylic oxime ester derivatives5a∼5o were tested according to reported work [31, 32]. The antifungal activities of compounds 5a-5o and fluxapyroxad were tested in vitro against Gibberella zeae (GZ), Fusarium oxysporum (FO), Phytophthora infestans (PI), Phytophthora capsici (PC), Rhizoctonia solani (RS), Sclerotinia sclerotiorum (SS), Alternaria solani (AS), Physalospora piricola (PP), Cercospora arachidicola (CA), and Botrytis cinerea (BC). The relative percent inhibition (%) has been determined using the mycelium growth rate method. The inhibition of the test compounds compared to the blank assay was calculated via the following equation:(1)inhibition%=CK−CICK×100%,where CK is the average diameter of mycelia in the blank test and CI is the average diameter of mycelia in the presence of those compounds. All experiments were replicated three times.


## 3. Results and Discussion

### 3.1. Chemistry

The intermediate4 (pyrazole-4-carbonyl chloride) was prepared by a previously reported method [20] in four synthetic steps from commercial starting materials. For the intermediate substituted-benzaldehyde oximes (Scheme 1), commercially available substituted benzaldehydes were condensed with excess NH2OH·HCl and were used without purification. Finally, the oximes were condensed with acid chloride 4 to afford the target compounds as white or light-yellow solids 5a-5o (Scheme 2). From Figure 2, the torsion angles, C (6)-O (2)-N (3)-C (7) was 172.50 (15)°, which indicated the two C=N groups are E configuration.Scheme 1
The synthetic route of substituted oxime.Scheme 2
Design strategy of pyrazole oxime ester compounds5a∼5o.Figure 2
Molecular structure of (E)-4-methylbenzaldehyde (O)-(3-(difluoromethyl)-1-methyl-1 (H)-pyrazole-4-carbonyl) oxime.


### 3.2. Fungicidal Activity

Fungicidal activities of compounds5a∼5o and positive control fluxapyroxad against Rhizoctonia solani(RS), Phytophthora capsici(PC), Alternaria solani(AS), Pyricularia oryae(PO), Gibberella zeae(GZ), Botrytis cinerea(BC), Sclerotinia sclerotiorum(SS), Fusarium oxysporum(FO), Physalospora piricola(PP), and Cercospora arachidicolawere tested at 50 ppm, the results are shown in Table 2. The fungicidal activity results showed some compounds exhibited good inhibition against S. sclerotiorum, B. cinerea, P. oryae, R. solani, and P. piricola. For the P. oryae, compounds 5g (85.7%) and 5j (71.4%) possessed good inhibition, compared to that of the control fluxapyroxad (27.3%). Compound 5k (42.9%) exhibited moderate activity against P. oryae. For S. sclerotiorum, compounds 5f (60.7%) and 5i (71.4%) possessed good inhibition, but was weaker than that of fluxapyroxad (96.4%). While compound 5b (44.6%), 5g (44.6%), 5h (53.6%), 5k (50.0%), and 5n (44.6%) displayed moderate activity against S. sclerotiorum. For R. solani, compound 5e (62.1%) possessed good inhibition, however, it was weaker than the control fluxapyroxad (88.4%). Compound 5c (43.1%), 5f (44.8%), 5h (50.0%), and 5j (55.2%) exhibited moderate activity against R. solani. For B. cinerea, only compound 5h (75.0%) possessed good inhibition. For P. piricola, compound 5e (53.1%), 5h (46.9%), 5j (62.5%), and 5o (56.3%) possessed moderate activity. Most of the title pyrazole oxime ester compounds showed weak activity against A. solani, G. zeae, P. capsici, F. oxysporum, and C. arachidicola.Table 2
The fungicidal activity of compounds5a∼5o at 50 ppm.
No.RASGZPOPCSSBCRSFOCAPP5aH27.8 ± 0.112.2 ± 0.128.6 ± 0.45.3 ± 0.117.9 ± 0.39.4 ± 0.332.8 ± 0.27.7 ± 0.117.6 ± 0.115.6 ± 0.25b2-CH311.1 ± 0.212.2 ± 0.117.1 ± 0.410.5 ± 0.144.6 ± 0.312.5 ± 0.420.7 ± 0.119.2 ± 0.317.6 ± 0.125.0 ± 0.25c3-CH316.7 ± 0.212.2 ± 0.114.3 ± 0.510.5 ± 0.217.9 ± 0.13.1 ± 0.343.1 ± 0.315.4 ± 0.123.5 ± 0.131.3 ± 0.25d4-CH333.3 ± 0.312.2 ± 0.317.1 ± 0.25.3 ± 0.125.0 ± 0.49.4 ± 0.337.9 ± 0.17.7 ± 0.117.6 ± 0.131.3 ± 0.15e2- OCH327.8 ± 0.329.3 ± 0.114.3 ± 0.113.2 ± 0.117.9 ± 0.312.5 ± 0.162.1 ± 0.319.2 ± 0.429.4 ± 0.153.1 ± 0.15f4- OCH316.7 ± 0.122.0 ± 0.128.6 ± 0.15.3 ± 0.260.7 ± 0.118.8 ± 0.144.8 ± 0.119.2 ± 0.417.6 ± 0.19.4 ± 0.25g3,4,5-tri-OCH333.3 ± 0.112.2 ± 0.185.7 ± 0.17.9 ± 0.244.6 ± 0.418.8 ± 0.129.3 ± 0.115.4 ± 0.117.6 ± 0.13.1 ± 0.15h2-Br16.7 ± 0.217.1 ± 0.314.3 ± 0.15.3 ± 0.153.6 ± 0.175.0 ± 0.350.0 ± 0.323.1 ± 0.329.4 ± 0.346.9 ± 0.35i4-Br11.1 ± 0.412.2 ± 0.128.6 ± 0.45.3 ± 0.171.4 ± 0.118.8 ± 0.137.9 ± 0.115.4 ± 0.111.8 ± 0.131.3 ± 0.15j2-NO25.6 ± 0.212.2 ± 0.171.4 ± 0.118.4 ± 0.27.1 ± 0.325.0 ± 0.455.2 ± 0.123.1 ± 0.147.1 ± 0.162.5 ± 0.15k4-NO25.6 ± 0.112.2 ± 0.242.9 ± 0.15.3 ± 0.150.0 ± 0.112.5 ± 0.127.6 ± 0.519.2 ± 0.117.6 ± 0.43.1 ± 0.35l4-F11.1 ± 0.112.2 ± 0.128.6 ± 0.210.5 ± 0.321.4 ± 0.334.4 ± 0.134.5 ± 0.17.7 ± 0.317.6 ± 0.112.5 ± 0.15m4-CF35.6 ± 0.312.2 ± 0.114.3 ± 0.15.3 ± 0.132.1 ± 0.19.4 ± 0.517.2 ± 0.37.7 ± 0.35.9 ± 0.328.1 ± 0.35n4-Cl16.7 ± 0.317.1 ± 0.117.1 ± 0.35.3 ± 0.144.6 ± 0.125.0 ± 0.137.9 ± 0.119.2 ± 0.117.6 ± 0.128.1 ± 0.35o2,4-di-Cl11.1 ± 0.212.2 ± 0.114.3 ± 0.15.3 ± 0.17.1 ± 0.312.5 ± 0.220.7 ± 0.515.4 ± 0.417.6 ± 0.256.3 ± 0.4CK88.9 ± 0.228.6 ± 0.227.3 ± 0.216.7 ± 0.296.4 ± 0.263.6 ± 0.288.4 ± 0.229.4 ± 0.2100 ± 0.263.6 ± 0.2


### 3.3. Docking Study

In order to study the mode of action of these compounds, molecular docking was carried out between the compound5g and the enzyme SDH (PDB:2FBW) using DS 2.5. The docking results indicated that compound 5g can well occupy the active site of SDH (Figure 3). From Figure 3 (above), two π-cation interactions exist between Arg 43 amino acid residue of SDH and the compound 5g with the distances of 3.6 Å and 3.9 Å, respectively. There are two hydrogen bonds between the compound 5g and SDH. One is between the Ser 39 amino acid residue of SDH and the O atom of carboxamide group in compound 5g and with the distance of 2.3 Å. The other is between the Tyr 58 amino acid residue of SDH and the O atom of MeO group with the distance of 2.0 Å. From the docking results, the pyrazole ring and amide group are key active groups in this fungicide, which is the same as the lead compound pydiflumetofen (Figure 3).Figure 3
Docking modeling and molecular receptor-ligand interactions of compound 5g (above, left 3D, right 2D) and CK (down, left 3D, right 2D) with SDH.


## 3.1. Chemistry

The intermediate4 (pyrazole-4-carbonyl chloride) was prepared by a previously reported method [20] in four synthetic steps from commercial starting materials. For the intermediate substituted-benzaldehyde oximes (Scheme 1), commercially available substituted benzaldehydes were condensed with excess NH2OH·HCl and were used without purification. Finally, the oximes were condensed with acid chloride 4 to afford the target compounds as white or light-yellow solids 5a-5o (Scheme 2). From Figure 2, the torsion angles, C (6)-O (2)-N (3)-C (7) was 172.50 (15)°, which indicated the two C=N groups are E configuration.Scheme 1
The synthetic route of substituted oxime.Scheme 2
Design strategy of pyrazole oxime ester compounds5a∼5o.Figure 2
Molecular structure of (E)-4-methylbenzaldehyde (O)-(3-(difluoromethyl)-1-methyl-1 (H)-pyrazole-4-carbonyl) oxime.


## 3.2. Fungicidal Activity

Fungicidal activities of compounds5a∼5o and positive control fluxapyroxad against Rhizoctonia solani(RS), Phytophthora capsici(PC), Alternaria solani(AS), Pyricularia oryae(PO), Gibberella zeae(GZ), Botrytis cinerea(BC), Sclerotinia sclerotiorum(SS), Fusarium oxysporum(FO), Physalospora piricola(PP), and Cercospora arachidicolawere tested at 50 ppm, the results are shown in Table 2. The fungicidal activity results showed some compounds exhibited good inhibition against S. sclerotiorum, B. cinerea, P. oryae, R. solani, and P. piricola. For the P. oryae, compounds 5g (85.7%) and 5j (71.4%) possessed good inhibition, compared to that of the control fluxapyroxad (27.3%). Compound 5k (42.9%) exhibited moderate activity against P. oryae. For S. sclerotiorum, compounds 5f (60.7%) and 5i (71.4%) possessed good inhibition, but was weaker than that of fluxapyroxad (96.4%). While compound 5b (44.6%), 5g (44.6%), 5h (53.6%), 5k (50.0%), and 5n (44.6%) displayed moderate activity against S. sclerotiorum. For R. solani, compound 5e (62.1%) possessed good inhibition, however, it was weaker than the control fluxapyroxad (88.4%). Compound 5c (43.1%), 5f (44.8%), 5h (50.0%), and 5j (55.2%) exhibited moderate activity against R. solani. For B. cinerea, only compound 5h (75.0%) possessed good inhibition. For P. piricola, compound 5e (53.1%), 5h (46.9%), 5j (62.5%), and 5o (56.3%) possessed moderate activity. Most of the title pyrazole oxime ester compounds showed weak activity against A. solani, G. zeae, P. capsici, F. oxysporum, and C. arachidicola.Table 2
The fungicidal activity of compounds5a∼5o at 50 ppm.
No.RASGZPOPCSSBCRSFOCAPP5aH27.8 ± 0.112.2 ± 0.128.6 ± 0.45.3 ± 0.117.9 ± 0.39.4 ± 0.332.8 ± 0.27.7 ± 0.117.6 ± 0.115.6 ± 0.25b2-CH311.1 ± 0.212.2 ± 0.117.1 ± 0.410.5 ± 0.144.6 ± 0.312.5 ± 0.420.7 ± 0.119.2 ± 0.317.6 ± 0.125.0 ± 0.25c3-CH316.7 ± 0.212.2 ± 0.114.3 ± 0.510.5 ± 0.217.9 ± 0.13.1 ± 0.343.1 ± 0.315.4 ± 0.123.5 ± 0.131.3 ± 0.25d4-CH333.3 ± 0.312.2 ± 0.317.1 ± 0.25.3 ± 0.125.0 ± 0.49.4 ± 0.337.9 ± 0.17.7 ± 0.117.6 ± 0.131.3 ± 0.15e2- OCH327.8 ± 0.329.3 ± 0.114.3 ± 0.113.2 ± 0.117.9 ± 0.312.5 ± 0.162.1 ± 0.319.2 ± 0.429.4 ± 0.153.1 ± 0.15f4- OCH316.7 ± 0.122.0 ± 0.128.6 ± 0.15.3 ± 0.260.7 ± 0.118.8 ± 0.144.8 ± 0.119.2 ± 0.417.6 ± 0.19.4 ± 0.25g3,4,5-tri-OCH333.3 ± 0.112.2 ± 0.185.7 ± 0.17.9 ± 0.244.6 ± 0.418.8 ± 0.129.3 ± 0.115.4 ± 0.117.6 ± 0.13.1 ± 0.15h2-Br16.7 ± 0.217.1 ± 0.314.3 ± 0.15.3 ± 0.153.6 ± 0.175.0 ± 0.350.0 ± 0.323.1 ± 0.329.4 ± 0.346.9 ± 0.35i4-Br11.1 ± 0.412.2 ± 0.128.6 ± 0.45.3 ± 0.171.4 ± 0.118.8 ± 0.137.9 ± 0.115.4 ± 0.111.8 ± 0.131.3 ± 0.15j2-NO25.6 ± 0.212.2 ± 0.171.4 ± 0.118.4 ± 0.27.1 ± 0.325.0 ± 0.455.2 ± 0.123.1 ± 0.147.1 ± 0.162.5 ± 0.15k4-NO25.6 ± 0.112.2 ± 0.242.9 ± 0.15.3 ± 0.150.0 ± 0.112.5 ± 0.127.6 ± 0.519.2 ± 0.117.6 ± 0.43.1 ± 0.35l4-F11.1 ± 0.112.2 ± 0.128.6 ± 0.210.5 ± 0.321.4 ± 0.334.4 ± 0.134.5 ± 0.17.7 ± 0.317.6 ± 0.112.5 ± 0.15m4-CF35.6 ± 0.312.2 ± 0.114.3 ± 0.15.3 ± 0.132.1 ± 0.19.4 ± 0.517.2 ± 0.37.7 ± 0.35.9 ± 0.328.1 ± 0.35n4-Cl16.7 ± 0.317.1 ± 0.117.1 ± 0.35.3 ± 0.144.6 ± 0.125.0 ± 0.137.9 ± 0.119.2 ± 0.117.6 ± 0.128.1 ± 0.35o2,4-di-Cl11.1 ± 0.212.2 ± 0.114.3 ± 0.15.3 ± 0.17.1 ± 0.312.5 ± 0.220.7 ± 0.515.4 ± 0.417.6 ± 0.256.3 ± 0.4CK88.9 ± 0.228.6 ± 0.227.3 ± 0.216.7 ± 0.296.4 ± 0.263.6 ± 0.288.4 ± 0.229.4 ± 0.2100 ± 0.263.6 ± 0.2


## 3.3. Docking Study

In order to study the mode of action of these compounds, molecular docking was carried out between the compound5g and the enzyme SDH (PDB:2FBW) using DS 2.5. The docking results indicated that compound 5g can well occupy the active site of SDH (Figure 3). From Figure 3 (above), two π-cation interactions exist between Arg 43 amino acid residue of SDH and the compound 5g with the distances of 3.6 Å and 3.9 Å, respectively. There are two hydrogen bonds between the compound 5g and SDH. One is between the Ser 39 amino acid residue of SDH and the O atom of carboxamide group in compound 5g and with the distance of 2.3 Å. The other is between the Tyr 58 amino acid residue of SDH and the O atom of MeO group with the distance of 2.0 Å. From the docking results, the pyrazole ring and amide group are key active groups in this fungicide, which is the same as the lead compound pydiflumetofen (Figure 3).Figure 3
Docking modeling and molecular receptor-ligand interactions of compound 5g (above, left 3D, right 2D) and CK (down, left 3D, right 2D) with SDH.


## 4. Conclusions

In conclusion, a series of pyrazole-4-carboxylic oxime ester derivatives were synthesized using a bioisosterism strategy. The X-ray analysis results showed that the oxime has anE configuration. The antifungal activity of the target pyrazole-4-carboxylic oxime ester compounds against ten fungi was tested at 50 ppm, and some of the target compounds showed good fungicidal activity against B. cinerea, S. sclerotiorum, R. solani, P. oryae, and P. piricola. These structures can be further optimized for discovering new fungicides.



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*Source: 6078017-2022-08-28.xml*