Regioselective [3 + 2] cycloaddition of di/trifluoromethylated hydrazonoyl chlorides with fluorinated nitroalkenes: a facile access to 3-di/trifluoroalkyl-5-fluoropyrazoles

Functionalization of Alkenes with Difluoromethyl Nitrile Oxide to Access the Difluoromethylated Derivatives

Electron-rich, electron-deficient, and non-activated alkenes can be rapidly functionalized by in situ-generated difluoromethyl nitrile oxide. The (3+2) cycloaddition proceeds at room temperature, has broad functional group tolerance, and can be used for the late-stage modification of bioactive molecules (finasteride and carbamazepine). The obtained CF2H-isoxazolines can be easily transformed into CF2H-containing building blocks for medicinal chemistry: amines, amino acids, amino alcohols, and spirocyclic scaffolds.

Electron Donor-Acceptor Complex Enabled Radical Cyclization of α-Diazodifluoroethyl Sulfonium Salt with Unactivated Alkynes

An α-diazodifluoroethane sulfonium reagent was developed in this study to undergo [3 + 2] radical cyclization with unactivated alkynes to give the corresponding 3-difluoromethyl pyrazoles under blue light irradiation conditions. The key to the success of this transformation lies in the formation of an electron donor-acceptor (EDA) complex between an electron-deficient α-diazo sulfonium salt and an electron-rich triaryl amine. This study circumvents a major substrate scope limitation in polar cycloaddition reactions of existent diazodifluoroethane reagents.

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

Nitrogen-containing organofluorine derivatives, which are prepared using fluorinated building blocks, are among the most important active fragments in various pharmaceutical and agrochemical products. This review focuses on the reactivity, synthesis, and applications of fluoromethylated hydrazones and acylhydrazones. It summarizes recent methodologies that have been used for the synthesis of various nitrogen-containing organofluorine compounds.

(3+2)-Cycloadditions of Levoglucosenone (LGO) with Fluorinated Nitrile Imines Derived from Trifluoroacetonitrile: An Experimental and Computational Study

The in situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile smoothly undergo (3+2)-cycloadditions onto the enone fragment of the levoglucosenone molecule, yielding the corresponding, five-membered cycloadducts. In contrast to the 'classic' C(Ph),N(Ph) nitrile imine, reactions with fluorinated C(CF3),N(Ar) analogues lead to stable pyrazolines in a chemo- and stereoselective manner. Based on the result of X-ray single crystal diffraction analysis, their structures were established as exo-cycloadducts with the location of the N-Ar terminus of the 1,3-dipole at the α-position of the enone moiety. The DFT computation demonstrated that the observed reaction pathway results from the strong dominance of kinetic control over thermodynamic control.

Synthesis of fused 3-trifluoromethyl-1,2,4-triazoles via base-promoted [3 + 2] cycloaddition of nitrile imines and 1H-benzo[d]imidazole-2-thiols

Here we report a strategy for the facile assembly of fused 3-trifluoromethyl-1,2,4-triazoles, which are difficult to synthesize using traditional strategies, in 50-96% yields through a triethylamine-promoted intermolecular [3 + 2] cycloaddition pathway. This protocol features high efficiency, good functional group tolerance, mild conditions, and easy operation. Furthermore, a gram-scale reaction and product derivatizations were carried out smoothly to illustrate the practicability of this method.