A series of novel 1,2,4-triazole derivatives containing oxime ether and phenoxy pyridine moiety were designed and synthesized. The new compounds were identified by nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS). Compound (Z)-1-(6-(4-nitrophenoxy)pyridin-3-yl)-2-(1H-1,2,4-triazol-1-yl)ethan-1-one O-methyl oxime (5a18) was further confirmed by X-ray single crystal diffraction. Their antifungal activities were evaluated against eight phytopathogens. The in vitro bioassays indicated that most of the title compounds displayed moderate to high fungicidal activities. Compound (Z)-1-(6-(4-bromo-2-chlorophenoxy)pyridin-3-yl)-2-(1H-1,2,4-triazol-1-yl)ethan-1-one O-methyl oxime (5a4) exhibited a broad-spectrum antifungal activities with the EC50 values of 1.59, 0.46, 0.27 and 11.39 mg/L against S. sclerotiorum, P. infestans, R. solani and B. cinerea, respectively. Compound (Z)-1-(6-(2-chlorophenoxy)pyridin-3-yl)-2-(1H-1,2,4-triazol-1-yl)ethan-1-one O-benzyl oxime (5b2) provided the lowest EC50 value of 0.12 mg/L against S. sclerotiorum, which were comparable to the commercialized difenoconazole. Moreover, homologous modeling and molecular docking disclosed possible binding modes of compounds 5a4 and 5b2 with CYP51. This work provided useful guidance for the discovery of new 1,2,4-triazole fungicides.
β,γ-Unsaturated α-ketoester is a class of polyfunctional synthon. Due to its 1,2-dicarbonyl structure and multiple reactive sites, it has been used for the synthesis of various compounds. In the past twenty years, a number of chiral Lewis acid catalysts and organocatalysts have been applied to asymmetric catalytic reactions using β,γ-unsaturated α-ketoesters and various optically active compounds have been synthesized. The current progress of β,γ-unsaturated α-ketoesters in asymmetric catalysis according to the three different reaction sites, unsaturated acyl conjugate system, carbon-carbon double bond and carbonyl group, is summarized. Finally, the limitation of related reactions and the future development trends are also pointed out.
The first Ni(II)-catalyzed asymmetric [4 + 2] cycloaddition of silyloxyvinylindoles with 2-enoyl pyridines was successfully accomplished by using a diphenylmethylidene-tethered bis (oxazoline). A series of optically active hydrocarbazole derivatives with three contiguous stereocenters were achieved in good yield with both high diastereo-(> 20 : 1) and enantioeselectivities (up to 97 % ee) under mild conditions. Moreover, various 2-enoyl azaarenes were compatible with the reaction. A proposed mechanism was deducted.
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