Trifluoromethylation of Secondary Nitroalkanes

Copper-Catalyzed α-Arylation of Nitroalkanes with (Hetero)aryl Bromides/Iodides

α-Aryl substituted nitroalkanes are valuable synthetic building blocks that can be easily converted into α-aryl substituted aldehydes, ketones, carboxylic acids, as well as amines. Herein, an efficient Cu/oxalamide-catalyzed coupling between nitroalkanes and (hetero)aryl halides (Br, I) was developed to direct access highly diverse α-aryl substituted nitroalkanes. Compared with the current state of art, this protocol is more environmentally friendly and practical for synthetic chemists. This approach is characterized by a broad substrate scope on both nitroalkane part (primary nitroalkanes and nitromethane) and sp2 halide part ((hetero)aryl bromides/iodides and alkenyl bromides/iodides). The excellent functional group tolerance was observed, which would enable real world synthetic applications. More importantly, TON of current transformation reached to 3640, when some aryl iodides were used as coupling partners. This represents currently the highest catalyst turnover for transition-metal catalyzed α-arylation of nitroalkanes. Furthermore, the successful application in late-stage modification of complex molecules and synthesis of a known retinoid X receptor (RXR) antagonist exemplified its synthetic potential.

Three-Component cine,ipso-Disubstitution of Nitrocoumarins

The development of a three-component cine,ipso-disubstitution of nitrocoumarins is reported. The reaction leverages the electrophilicity of nitrocoumarins, the nucleophilicity of nitronates, and the leaving group ability of nitrite (NO2-) to yield complex polyfunctionalized biaryls that often display stable axial chirality.

Photoredox-Nickel Dual-Catalyzed C-Alkylation of Secondary Nitroalkanes: Access to Sterically Hindered α-Tertiary Amines

The preparation of tertiary nitroalkanes via the nickel-catalyzed alkylation of secondary nitroalkanes using aliphatic iodides is reported. Previously, catalytic access to this important class of nitroalkanes via alkylation has not been possible due to the inability of catalysts to overcome the steric demands of the products. However, we have now found that the use of a nickel catalyst in combination with a photoredox catalyst and light leads to much more active alkylation catalysts. These can now access tertiary nitroalkanes. The conditions are scalable as well as air and moisture tolerant. Importantly, reduction of the tertiary nitroalkane products allows rapid access to α-tertiary amines.

Synthesis and applications of S-(trifluoromethyl)-2,8-bis(trifluoromethoxy)dibenzothiophenium triflate (Umemoto reagent IV)

A new, powerful, and easy-to-handle electrophilic trifluoromethylating agent, S-(trifluoromethyl)-2,8-bis(trifluoromethoxy)dibenzothiophenium triflate (Umemoto reagent IV), was developed. Due to the extraordinary electronic effect of trifluoromethoxy group, Umemoto reagent IV was easily synthesized by a one-pot method from readily available 3,3'-bis(trifluoromethoxy)biphenyl. It was shown that Umemoto reagent IV was more powerful than Umemoto reagent II and could trifluoromethylate many kinds of nucleophilic substrates more effectively. In addition, Umemoto reagent IV was successfully utilized for the preparation of trifluoromethyl nonaflate, a useful trifluoromethoxylating agent. The direct conversion of 2,8-bis(trifluoromethoxy)dibenzothiophene to Umemoto reagent IV with triflic anhydride was achieved, albeit in low yield.

Leveraging Electron‐Deficient Iminium Intermediates in a General Synthesis of Valuable Amines

The development of reactions converting alkenes and alkynes into valuable building blocks remains one of the main goals of synthetic chemistry. Herein, we present the leveraging of highly electron‐deficient iminium ions, rare and fleeting intermediates, into a general amine synthesis. This enables the preparation of amines bearing e.g. valuable α‐trifluoromethyl moieties under mild conditions. This broad concept is highlighted by the late‐stage amination of quinine into a biologically interesting new analogue.

Nutzung von elektronenarmen Iminiumintermediaten zur Synthese von wertvollen Aminen

Die Entwicklung von Reaktionen zur Umwandlung von Alkenen und Alkinen in wertvolle Bausteine ist nach wie vor eines der Hauptziele in der synthetischen Chemie. In dieser Arbeit berichten wir von der Nutzbarmachung von stark elektronenarmen, seltenen und kurzlebigen Iminiumionen zur Synthese von Aminen. Dies ermöglicht die milde Herstellung von Aminen mit z. B. trifluormethylierten Einheiten. Dieses umfassende Konzept wird durch die Aminierung von Chinin zu einem biologisch interessanten neuen Analogon verdeutlicht.

Construction of fully substituted carbon centers containing a heteroatom and a CF3 group via in situ generated p-quinone methides

1,6-Conjugate additions of in situ generated δ-CF3-δ-substituted p-quinone methides have been achieved with a variety of heteronucleophiles under mild conditions, which led to facile and practical construction of fully substituted carbon centers including a heteroatom and a CF3 group. In particular, it was revealed that some amines themselves worked for efficient cleavage of the TBS protective group, and addition of a catalytic amount of an appropriate Brønsted acid was found to sometimes improve the progress of the desired process.

Photocatalyst and additive-free visible light induced trifluoromethylation-arylation of N-arylacrylamides with Umemoto's reagent

A visible light induced highly convenient and practical method for the trifluoromethyl-arylation of N-arylmethacrylamides has been developed using Umemoto's reagent as the trifluoromethyl source. This user-friendly approach can proceed under visible light irradiation without any transition metal, photocatalyst and additive at room temperature. The strategy presented here provides access to trifluoromethylated oxindoles in good to excellent yields with a broad functional group tolerance. Preliminary mechanistic experiments indicated that the reaction process involves a homolytic cleavage of Umemoto's reagent irradiated by visible light.

Copper-Catalyzed Enantioselective Synthesis of Oxazolines from Aminotriols via Asymmetric Desymmetrization

A copper-catalyzed enantioselective transformation of tris(hydroxymethyl)aminomethane-derived aminotriols was developed to provide multisubstituted oxazolines with a tetrasubstituted carbon center. The present transformation consisted of sequential reactions involving mono-sulfonylation of aminotriols, subsequent intramolecular cyclization to afford prochiral oxazoline diols, and sulfonylative asymmetric desymmetrization of resultant oxazoline diols. In addition, the kinetic resolution process would be involved in the sulfonylative asymmetric desymmetrization step, which would amplify the enantiopurities of the desired products. Various aminotriols were tolerated in the present reaction, affording the desired oxazolines in good to high yields with excellent enantioselectivities. The synthetic utility of the present reaction was demonstrated by the transformation of the optically active oxazoline into a chiral α-tertiary amine motif.

Metal-Free Construction of the C(sp3)-CF3 Bond: Trifluoromethylation of Hydrazones with Togni's Reagent under Mild Conditions

A metal-free trifluoromethylation of hydrazones with Togni's reagent under mild conditions was developed. Various functional groups including ester, methoxy, dimethoxy, nitro, halogen, and heterocyclic compounds were tolerated. This simple and green strategy provides a practical tool to construct C(sp³)-CF₃ bonds.

Nickel-Catalyzed Asymmetric C-Alkylation of Nitroalkanes: Synthesis of Enantioenriched β-Nitroamides

A general catalytic method for asymmetric C-alkylation of nitroalkanes using nickel catalysis is described. This method enables the formation of highly enantioenriched β-nitroamides from readily available α-bromoamides using mild reaction conditions that are compatible with a wide range of functional groups. When combined with subsequent reactions, this method allows access to highly enantioenriched products with nitrogen-bearing fully substituted carbon centers.

Copper-catalyzed regioselective cyclization of vinyl azides by gem-difluoromethylene for trisubstituted pyridines

A novel copper-catalyzed cyclization of readily available vinyl azides with gem-difluoromethylene is described.

Synthesis of Optically Active α-Trifluoromethylamines by Rearrangement of β-Amino-α-trifluoromethyl Alcohols

The synthesis of various optically active α-trifluoromethylamines has been realized from β-amino-α-trifluoromethyl alcohols via an aziridinium ion intermediate under kinetic conditions.

An ab initio and DFT study of trifluoromethylation using Umemoto's reagent

Theoretical calculations revealed that trifluoromethylation using Umemoto's reagent would occur through the ionic backside mechanism.