Fluoroalkyl Amino Reagents for the Introduction of the Fluoro(trifluoromethoxy)methyl Group onto Arenes and Heterocycles

Methyl 4-amino-3-meth-oxy-isoxazole-5-carboxyl-ate

The title compound, C6H8N2O4, a new derivative of isoxazole, has been synthesized and structurally characterized. The crystal structure shows the mol-ecule to be almost planar (r.m.s. deviation for the non-hydrogen atoms = 0.029 Å), this conformation being supported by an intra-molecular N-H⋯O hydrogen bond. In the extended structure, the mol-ecules are linked by N-H⋯O hydrogen bonds into chains propagating along [010].

Silver-Catalyzed Trifluoromethoxylation of Aziridines

We disclose a silver-catalyzed trifluoromethoxylation of N-tosyl aziridines with trifluoromethyl arylsulfonate. The protocol is characterized by its mild conditions, simple operations, and good chemo- and regioselectivity. In addition, the trifluoromethoxylation of trisubstituted aziridines could construct C-OCF₃ quaternary centers exclusively, which is quite rare. This method unlocks a new catalytic blueprint for accessing β-trifluoromethoxylated amines, which could be important building blocks in synthetic chemistry.

Pyrazole Scaffold Synthesis, Functionalization, and Applications in Alzheimer's Disease and Parkinson's Disease Treatment (2011-2020)

The remarkable prevalence of pyrazole scaffolds in a versatile array of bioactive molecules ranging from apixaban, an anticoagulant used to treat and prevent blood clots and stroke, to bixafen, a pyrazole-carboxamide fungicide used to control diseases of rapeseed and cereal plants, has encouraged both medicinal and organic chemists to explore new methods in developing pyrazole-containing compounds for different applications. Although numerous synthetic strategies have been developed in the last 10 years, there has not been a comprehensive overview of synthesis and the implication of recent advances for treating neurodegenerative disease. This review first presents the advances in pyrazole scaffold synthesis and their functionalization that have been published during the last decade (2011-2020). We then narrow the focus to the application of these strategies in the development of therapeutics for neurodegenerative diseases, particularly for Alzheimer's disease (AD) and Parkinson's disease (PD).

Formation of synthetically relevant CF3-substituted phenonium ions in superacid media

Under superacidic conditions, CF₃-substituted phenonium ions can be generated to furnish original CF₃-substituted dihydrostilbenes of interest.

Copper(II)-Catalyzed Domino Synthesis of 4-Benzenesulfonyl Isoxazoles from 2-Nitro-1,3-enynes, Amines, and Sodium Benzenesulfinate

A simple and effective method for the synthesis of fully substituted 4-benzenesulfonyl isoxazoles through a copper(II)-catalyzed three-component reaction of 2-nitro-1,3-enynes, amines, and sodium benzenesulfinate is described. The reaction proceeds smoothly under mild conditions and provides the benzenesulfonyl isoxazoles with high chemoselectivity.

Synthesis of Fluorinated Amide Derivatives via a Radical N-Perfluoroalkylation-Defluorination Pathway

A one-pot approach to fluorinated hydroxamic acid, amide, and thioamide derivatives is reported. The reaction proceeds via an N-perfluoroalkylation of nitrosoarenes with perfluoroalkanesulfinates, resulting in labile N-perfluoroalkylated hydroxylamines. By the addition of suitable additives, a controllable oxy/thiodefluorination of the fluorinated hydroxylamine intermediates was achieved. The method highlights N-perfluoroalkylated amines as versatile intermediates for further synthesis.

Silver-mediated oxidative functionalization of alkylsilanes

A general approach to the functionalization of aliphatic C-Si bonds in the presence of silver salts and oxidants has been reported. This strategy encompasses a range of valuable C-Si transformations, including the direct conversions of a C-Si bond to C-OCF3, C-OBz, C-OCOCF3, C-SCF3, C-SCN, and C-N3 bonds. Among them, trifluoromethoxylation of alkylsilanes is reported for the first time. In addition, mechanistic studies indicate that this reaction may proceed through a radical mechanism.

Hydroximoyl fluorides as the precursors of nitrile oxides: synthesis, stability and [3 + 2]-cycloaddition with alkynes

The transformation of hydroximoyl fluorides to nitrile oxides for [3 + 2]-cycloaddition with alkynes has been achieved for the first time. The hydroximoyl fluorides used in this work appeared to be not stable, which was proved by a series of experiments. A DFT calculation was performed to better understand the properties of hydroximoyl fluorides. Although not stable, the hydroximoyl fluorides could be successfully converted to the corresponding nitrile oxides for in situ [3 + 2]-cycloaddition with alkynes to yield the isoxazoles. Furthermore, it was feasible to conduct [3 + 2]-cycloaddition reaction without purification after the synthesis of hydroximoyl fluorides from gem-difluoroalkenes. By investigating a class of interesting yet previously rarely explored fluorinated compounds, this work sheds new light on the stability and reactivity of a C-F bond on a C[double bond, length as m-dash]N double bond.

Cobalt-Catalyzed Trifluoromethoxylation of Epoxides

A catalytic ring-opening reaction of epoxides by nucleophilic trifluoromethoxylation of trifluoromethyl arylsulfonate has been developed based on the use of a cobalt catalyst. This reaction provides an efficient, simple route for directly construction of a wide range of vicinal trifluoromethoxyhydrins under mild conditions. In addition, this method can convert terminal epoxides into target products with good chemo- and regioselectivity.

Silver-Promoted Oxidative Benzylic C-H Trifluoromethoxylation

A silver-promoted oxidative benzylic C-H trifluoromethoxylation has been reported for the first time. With trifluoromethyl arylsulfonate as the trifluoromethoxylation reagent, various arenes, having diverse functional groups, undergo trifluoromethoxylation of their benzylic C-H bonds to form trifluoromethyl ethers under mild reaction conditions. In addition, the trifluoromethoxylation and the fluorination of methyl groups of electron-rich arenes have been achieved to prepare α-fluorobenzyl trifluoromethyl ethers in one step.

Direct Dehydroxytrifluoromethoxylation of Alcohols

The first example of a direct dehydroxytrifluoromethoxylation of alcohols has been developed. This method generated an alkyl fluoroformate in situ from alcohols, followed by nucleophilic trifluoromethoxylation with trifluoromethyl arylsulfonate (TFMS) as the trifluoromethoxylation reagent. The reaction is operationally simple and scalable, and it proceeds under mild reaction conditions to provide access to a wide range of trifluoromethyl ethers from alcohols. In addition, this method is suitable for the late-stage trifluoromethoxylation of complex small molecules.