Synthesis of fluazolate via the application of regioselective [3+2] cyclocondensation and nucleophilic substitution-cyclization strategies

Design, Synthesis, and Biological Activity Determination of Novel Phenylpyrazole Protoporphyrinogen Oxidase Inhibitor Herbicides Containing Five-Membered Heterocycles

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) inhibitor herbicides have attracted widespread attention in recent years as ideal herbicides due to their high efficiency, low toxicity, and low pollution. In this article, 30 phenylpyrazole derivatives containing five-membered heterocycles were designed and synthesized according to the principle of bioelectronic isoarrangement and active substructure splicing. A series of structural characterizations were performed on the synthesized compounds. The herbicide activity in greenhouse was evaluated to determine their growth inhibition effect on weeds, their IC50 value through in vitro PPO enzyme activity measurement was calculated, and target compounds 2i and 3j that have herbicide effects comparable to pyraflufen-ethyl were selected. Crop safety experiments have shown that when the spraying concentration is 300 g of ai/ha, gramineous crops such as wheat, corn, and rice are more tolerant to compound 2i, with wheat exhibiting high tolerance, which is equivalent to the crop safety of pyraflufen-ethyl. Compound 2i can be used as a candidate herbicide for wheat, corn, and paddy fields, and the results are consistent with the cumulative concentration experiment. Molecular docking results showed that compound 2i interacted with the amino acid residue ARG-98 by forming two hydrogen bonds and interacted with the amino acid residue PHE-392 by forming two π-π stacking interactions, indicating that compound 2i has more excellent herbicidal activity than pyraflufen-ethyl and is expected to become a potential lead compound of phenylpyrazole PPO inhibitor herbicides.

Regioselective Synthesis of Functionalized 3- or 5-Fluoroalkyl Isoxazoles and Pyrazoles from Fluoroalkyl Ynones and Binucleophiles

A facile synthetic route toward either 3- or 5-fluoroalkyl-substituted isoxazoles or pyrazoles containing an additional functionalization site was developed and applied on a multigram scale. The elaborated approach extends the scope of fluoroalkyl substituents for introduction into the heterocyclic moiety, and uses convenient transformations of the side chain for incorporation of fluoroalkyl-substituted azoles into the structures of biologically active molecules. The utility of the obtained building blocks for isosteric replacement of alkyl-substituted isoxazole and pyrazole was shown by the synthesis of fluorinated Isocarboxazid and Mepiprazole analogues.

Electrophilic halogenation of hydrazones of CF3-ynones. Regioselective synthesis of 4-halo-substituted 3-CF3-pyrazoles

An efficient approach for the synthesis of 4-halo-3-CF3-pyrazoles was elaborated using the cyclization of hydrazones of CF3-ynones induced by electrophilic halogenation. This method can be used for the regioselective synthesis of 3-CF3-pyrazoles substituted at the 4-position with any halogen (I, Br or Cl). The high (up to quantitative) yields, mild conditions and simplicity of the reaction protocol are the advantages of the proposed method. It was demonstrated that cross-coupling with 4-iodo-3-CF3-pyrazoles can be used for the synthesis of a broad family of tetrasubstituted pyrazoles. Moreover, it was found that this method is suitable for the synthesis of 4-substituted derivatives of Celebrex and SC-560.