Nickel-catalyzed C H trifluoromethylation of pyridine N-oxides with Togni’s reagent

Visible Light-Induced Divergent Deoxygenation/Hydroxymethylation of Pyridine N-Oxides

This study explores the deoxygenation of pyridine N-oxides and presents a one-step photoredox method for the direct synthesis of 2-hydroxymethylated pyridines from pyridine N-oxides. Mechanism studies elucidate the role of the catalyst and provide evidence of the possible electron transfer process and the formation of key radicals. A range of pyridine derivatives, particularly 2-hydroxymethyl-substituted pyridines, which may be difficult to obtain, can be synthesized in a single step.

Metal-Free Synthesis of 2-(per)Fluoroalkyl-3-nitro Indoles via Intramolecular Cyclization of Amides

A metal-free intramolecular cyclization of N-acyl amides for the synthesis of 3-nitro-2-(per)fluoroalkyl indoles is reported. Good functional group tolerance and a broad range of substrates are the features of this approach. The developed method is easy to operate and is suitable for the preparation of 2-difluoromethyl/trifluoromethyl/perfluoroethyl/perfluoropropyl indoles in yields of 84 to 99%. Also, the application of this protocol in the gram scale is shown.

Regioselective C-H Trifluoromethylation and Its Related Reactions of (Hetero)aromatic Compounds

Fluorinated functional groups, including trifluoromethyl group, play important roles in the development of drugs, agrochemicals, and organic functional materials. Therefore, the development of highly effective and practical reactions to introduce fluorinated functional groups into (hetero)aromatic compounds is highly desirable. We have achieved several regioselective C-H trifluoromethylation and related reactions by electrophilic and nucleophilic activation of six-membered heteroaromatic compounds and steric protection of aromatic compounds. These reactions proceed in good to excellent yields, even on a gram scale, with high functional group tolerance, and are applicable to the regioselective trifluoromethylation of drug molecules. In this personal account, the background of the introduction reactions of fluorinated functional groups, our reaction designs to achieve regioselective C-H trifluoromethylation and the related reactions of (hetero)aromatic compounds are explained.

Recent Advances in Transition-Metal Mediated Trifluoromethylation Reactions

Fluorine compounds are known for their abundance in more than 20% of pharmaceutical and agrochemical products mainly due to the enhanced lipophilicity, metabolic stability and pharmacokinetic properties of organofluorides. Consequently,...

Photoinduced Trifluoromethylation of Arenes and Heteroarenes Catalyzed by High-Valent Nickel Complexes

We describe a series of air-stable Ni^III complexes supported by a simple, robust naphthyridine-based ligand. Access to the high-valent oxidation state is enabled by the CF₃ ligands on the nickel, while the naphthyridine exhibits either a monodentate or bidentate coordination mode that depends on the oxidation state and sterics, and enables facile aerobic oxidation of Ni^II to Ni^III . These Ni^III complexes act as efficient catalysts for photoinduced C(sp² )-H bond trifluoromethylation reactions of (hetero)arenes using versatile synthetic protocols. This blue LED light-mediated catalytic protocol proceeds via a radical pathway and demonstrates potential in the late-stage functionalization of drug analogs.

Synthesis of 2-trifluoromethylated quinolines from CF3-alkenes

α-CF₃-enamines can be prepared by the reaction of pyrrolidine with the corresponding haloalkenes. The prepared enamines react with 2-nitrobenzaldehydes to give ortho-nitro-substituted α,β-diaryl-CF₃-enones highly stereoselectively in up to 88% yield. Subsequent reduction of the nitro-group by an Fe-AcOH system promotes intramolecular cyclization to afford 2-CF₃-3-arylquinolines in up to 99% isolated yield. High synthetic utility of all synthetic steps of the sequence was shown. A one-pot procedure was developed to give the target trifluoromethylated quinolines directly from enamines or haloalkenes.

Transition-Metal-Free Oxidation of Benzylic C-H Bonds of Six-Membered N-Heteroaromatic Compounds

A novel oxidation of benzylic C-H bonds for the synthesis of diverse six-membered N-heteroaromatic aldehydes and ketones has been developed. The obvious advantages of this approach are the simple operation, mild reaction conditions, and without use of toxic reagent and transition metal. The present method should provide a useful access for the synthesis and modification of N-heterocycles.

Nickel-promoted C(2)–H amidation of quinoline N-oxides with N-fluorobenzenesulfonimide

The first example of nickel-promoted C–H amidation of quinoline N-oxides with NFSI.

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

Nickel-Catalyzed Direct C-H Trifluoromethylation of Free Anilines with Togni's Reagent

An efficient nickel-catalyzed C-H trifluoromethylation for the synthesis of trifluoromethylated free anilines using Togni's reagent has been developed. This approach exhibits a good functional group tolerance, good regioselectivity, and chemoselectivity under mild conditions. The newly developed economical one-step method is a better alternative to synthesize trifluoromethylated free anilines.

Bromide-catalyzed electrochemical trifluoromethylation/cyclization of N-arylacrylamides with low catalyst loading

An electro-generated trifluoromethyl radical mediated by a bromide ion is efficiently applied to the trifluoromethylarylation/cyclization of N-arylacrylamides.