Synthesis and Antifungal and Insecticidal Activities of Novel N-Phenylbenzamide Derivatives Bearing a Trifluoromethylpyrimidine Moiety

Seventeen novel N-phenylbenzamide derivatives bearing a trifluoromethylpyrimidine moiety were synthesized via four-step reactions..eir antifungal and insecticidal properties were evaluated. Antifungal test results demonstrated that some of the synthesized compounds showed better in vitro bioactivities against Phomopsis sp., Botryosphaeria dothidea (B. dothidea), and Botrytis cinerea (B. cinerea) at 50 μg/mL than pyrimethanil. Unfortunately, the synthesized compounds revealed lower insecticidal activities against Spodoptera frugiperda (S. frugiperda) and Mythimna separata (M. separata) at 500μg/mL than chlorantraniliprole.


Introduction
Plant fungal diseases and insect pests have drawn widespread attention because of their enormous damage toward agriculture [14]. e traditional commercial fungicides and insecticides used to prevent and control plant diseases could increase the yield, improve the quality of agricultural products, and also not reduced huge loss annually [5,6]. However, the misuse of traditional fungicides and insecticides had speeded up the resistance of plant diseases, which is rapidly becoming a huge challenge in agriculture [7,8]. erefore, it is still an urgent and meaningful task to develop the novel, highly efficient, and promising pesticides.
Herein, to develop new highly bioactivity lead compounds, we replace benzamide to N-phenylbenzamide ( Figure 2) to design a series of novel N-phenylbenzamide derivatives containing a trifluoromethylpyrimidine moiety and then evaluate their antifungal and insecticidal activities.

Materials and Methods.
e melting points were obtained by using an XT-4 binocular microscope (Beijing Tech. Instrument Co., China). NMR spectral recorded on a Bruker Avance NEO 600 NMR spectrometer (Bruker Corporation, MA, USA) using DMSO-d 6 as an solvent. HRMS data were obtained on a ermo Scientific Q Exactive Fucus instrument ( ermo Fisher Scientific, CA, USA). Analytical TLC was performed on silica gel GF 254 .  reacted for 0.5 h at reflux temperature. After that, diisopropylethylamine (0.12 mol) was added dropwise and continuously reacted for 8 h. After completion, excess POCl 3 and CH 3 CN were removed by distillation, and then icewater mixture (120 mL) was added. Finally, the mixture was alkalified with 5 mol/L NaOH to pH 9 and extracted using CH 2 Cl 2 to give intermediate 2.

General Procedure for the Preparation of the Target Compounds (4a-4q).
To a 50 mL round bottom flask, the key intermediate 3 (0.024 mol), dichloromethane (20 mL), aromatic amides (0.02 mol), dimethylaminopyridine (DMAP, 0.0004 mol), and 1-(3-dimethylaminopropyl)-3ethylcarbodiimide hydrochloride (EDCI, 0.03 mol) were added, respectively. e reaction was carried out at room temperature for 8-10 h. After the completion of the reaction, the solvent was evaporated under vacuum condition and then the residue was recrystallized from ethanol to give pure target compounds 4a-4q. e physical characteristics, 1 H NMR, 13 C NMR, and HRMS data for all the target compounds are shown in Supplementary Materials.

In Vitro Antifungal Activity Test.
e in vitro antifungal activities against Phomopsis sp., B. dothidea, and B. cinerea of the target compounds 4a-4q at 50 μg/mL were evaluated by the mycelium growth rate technique [32]. Each compound was dissolved in 1 mL DMSO and 9 mL 0.1% Twain aqueous solution, and then the mixture solution was added to 90 mL potato dextrose agar (PDA) medium to obtain 100 mL mixed PDA medium with the test compound concentration of 50 μg/mL. e mixed PDA mediums were poured into 6 dishes and cooled to room temperature to prepare PDA plates. en, approximately 0.4 cm diameter mycelia dishes were cut from culture medium and transferred to the middle of PDA plates with a germfree inoculation needle. After that, the inoculated PDA plates were fostered at 27 ± 1°C for 3-4 days. ree replicates were conducted for each treatment.
e following formula (1) was used to calculate the inhibition rates I (%), where C (cm) represents the diameter of fungi growth on untreated PDA and T (cm) represents the diameter of fungi on treated PDA: 2.6. Insecticidal Activity Test. e insecticidal activities against S. frugiperda and M. separata of the target compounds 4a-4q at 500 μg/mL were performed according to the reported methods [33]. Each compound was added to 0.1 mg/L NP-10 solvent to prepare the test compound solution with 500 µg/mL concentration. en, approximately 5 cm length maize leaves and 3 cm diameter sweet corn leaves were soaked into the mixed solutions for 10 s and then dried at room temperature and placed in the Petri dish. After that, 30 larvae of second-instar S. frugiperda and M. separata were transferred into the Petri dish and cultivated in the incubator at 27 ± 1°C for 48 h. ree replicates were performed for each treatment.
e mortality rates were determined using Abbott's formula.

Antifungal Activity Test in Vitro.
According to the antifungal activity data, the difference of R 1 and R 2 substituent groups was related to the antifungal activity of the target compounds. When the R 2 was the same group, with the presence of -H at R 1 , the target compound revealed higher antifungal activity than compound with the R 1 was -CH 3 . When R 1 was H, compounds with the presence of -F and -OCF 3 at R 2 represented higher antifungal activity compared with the other target compounds. Table 2 shows that the target compounds 4a-4p indicated lower insecticidal activities against S. frugiperda (10.0-86.7%) and M. separata (13.3-90.0%) at 500 µg/mL than those of chlorantraniliprole. Especially, compound 4h demonstrated an excellent mortality rate of 90.0% against M. separata as well as compounds 4o and 4q revealed moderate insecticidal activity against S. frugiperda with the mortality rates of 83.3% and 86.7%, respectively.

Conclusion
In summary, 17 novel N-phenylbenzamide derivatives containing a trifluoromethylpyrimidine moiety were prepared, and their structures were confirmed by 1 H NMR, 13 C NMR, and HRMS. Biological activity results indicated that most of the target compounds exhibited moderate to good antifungal and insecticidal activities. Among them, compound 4q revealed the best antifungal activities against Phomopsis sp., B. dothidea, and B. cinerea than those of pyrimethanil and the other target compounds. is study provided hope for discovery, development, design, and synthesis of novel N-phenylbenzamide derivatives containing a trifluoromethylpyrimidine.
Data Availability e datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest
All authors state that there are no conflicts of interest.