TBPEH-TBPB Initiate the Radical Addition of Benzaldehyde and Allyl Esters.

Tert-butylperoxy-2-ethylhexanoate (TBPEH) and tert-butyl peroxybenzoate (TBPB) promote the radical acylation of allyl ester with benzaldehyde to synthesize new carbonyl-containing compounds under solvent-free and metal-free conditions. This reaction is compatible with electron-donating and halogen groups and has excellent atom utilization and chemical selectivity. Furthermore, the synthetic compounds can further apply to the preparation of lactone, piperidine, tetrazole and oxazole.

Synthesis, biological activity and toxicity to zebrafish of benzamides substituted with pyrazole-linked 1,2,4-oxadiazole.

To find pesticidal lead compounds with high activity, a series of novel benzamides substituted with pyrazole-linked 1,2,4-oxadiazole was designed and synthesized by using the splicing principle of active substructures. The chemical structures of the target compounds were confirmed by 1H NMR, 13C NMR and HRMS. The preliminary bioassay showed that most compounds displayed good larvicidal activities against mosquito larvae at 10 mg L-1. In particular, compound 12g exhibited obvious activity; its lethal rate reached up to 100% (at 5 mg L-1) and 55% (at only 2 mg L-1). Furthermore, compound 12f (70.6%) and 12h (100%) showed good fungicidal activities against Pyricularia oryzae, with EC50 values of 8.28 and 5.49 µg mL-1, respectively, which were superior to that of the control drug bixafen (9.15 µg mL-1). Finally, the LC50 of compound 12h to zebrafish embryo was 0.39 mg L-1, so it was classified as a high-toxic compound. Thus, this compound may be used as a potential lead compound for further structural optimisation to develop new compounds with high activity and low toxicity.

Structure-Based Bioisosterism Design, Synthesis, Biological Activity and Toxicity of 1,2,4-Oxadiazole Substituted Benzamides Analogues Containing Pyrazole Rings.

In order to discover pesticidal lead compounds with high activity and low toxicity, a series of novel benzamides substituted with pyrazole-linked 1,2,4-oxadiazole were designed via bioisosterism. The chemical structures of the target compounds were confirmed via 1H NMR, 13C NMR and HRMS analysis. The preliminary bioassay showed that most compounds exhibited good lethal activities against Mythimna separate, Helicoverpa armigera, Ostrinia nubilalis and Spodoptera frugiperda at 500 mg/L. Particularly in the case of Mythimna separate, compound 14q (70%) exhibited obvious insecticidal activity. In addition, compound 14h demonstrated good fungicidal activity against Pyricularia oryae with an inhibition rate of 77.8%, and compounds 14e, 14k, 14n and 14r also showed certain antifungal activities (55.6-66.7%). The zebrafish toxicity test showed that the LC50 of compound 14h was 14.01 mg/L, which indicated that it may be used as a potential leading compound for further structural optimization.

Benzamides Substituted with Quinoline-Linked 1,2,4-Oxadiazole: Synthesis, Biological Activity and Toxicity to Zebrafish Embryo.

To develop new compounds with high activity, broad spectrum and low-toxicity, 17 benzamides substituted with quinoline-linked 1,2,4-oxadiazole were designed using the splicing principle of active substructures and were synthesized. The biological activities were evaluated against 10 fungi, indicating that some of the synthetic compounds showed excellent fungicidal activities. For example, at 50 mg/L, the inhibitory activity of 13p (3-Cl-4-Cl substituted, 86.1%) against Sclerotinia sclerotiorum was superior to that of quinoxyfen (77.8%), and the inhibitory activity of 13f (3-CF3 substituted, 77.8%) was comparable to that of quinoxyfen. The fungicidal activities of 13f and 13p to Sclerotinia sclerotiorum were better than that of quinoxyfen (14.19 mg/L), with EC50 of 6.67 mg/L and 5.17 mg/L, respectively. Furthermore, the acute toxicity of 13p was 19.42 mg/L, classifying it as a low-toxic compound.