Catalytic enantioselective trifluoromethylation of azomethine imines with trimethyl(trifluoromethyl)silane

1,3-Hydro-di/monofluoromethylation of N,N'-Cyclic Azomethine Imines with HCF2SO2Na/H2CFSO2Na via Photocatalytic Radical Addition

The radical 1,3-hydro-di/monofluoromethylation of N,N'-cyclic azomethine imines with HCF2SO2Na/H2CFSO2Na via photoredox catalysis is described. This reaction exhibits broad functional group compatibility, providing the desired products in good yields. However, CF3SO2Na failed to produce the trifluoromethyl product. DFT calculations revealed that the transition state activation energy for radical trifluoromethylation was significantly higher and the isotropic charge repulsion makes it difficult for the CF3 radical to transfer electrons.

Making Full Use of TMSCF3: Deoxygenative Trifluoromethylation/Silylation of Amides

As one of the most powerful trifluoromethylation reagents, (trifluoromethyl)trimethylsilane (TMSCF3) has been widely used for the synthesis of fluorine-containing molecules. However, to the best of our knowledge, the simultaneous incorporation of both TMS- and CF3- groups of this reagent onto the same carbon of the products has not been realized. Herein, we report an unprecedented SmI2/Sm promoted deoxygenative difunctionalization of amides with TMSCF3, in which both silyl and trifluoromethyl groups are incorporated into the final product, yielding α-silyl-α-trifluoromethyl amines with high efficiency. Notably, the silyl group could be further transformed into other functional groups, providing a new method for the synthesis of α-quaternary α-CF3-amines.

Asymmetric Mannich Reaction of Isatin-Derived Ketimines with α-Fluoroindanones Catalyzed by a Chiral Phase-Transfer Catalyst

A highly enantioselective Mannich reaction of α-fluoroindanones with isatin-derived N-Boc-ketimines catalyzed by a quinine-derived phase-transfer catalyst was developed. A variety of 3-substituted 3-amino-2-oxindoles bearing fluorine-containing, vicinal, tetrasubstituted stereocenters were constructed using this protocol in high yields (83-95%), with moderate to excellent enantioselectivities (66-91%) and high diastereoselectivities (up to >99:1).

Palladium-catalyzed enantioselective arylation of trichloro- or tri-/difluoroacetaldimine precursors

A palladium-catalyzed asymmetric α-arylation of N-carbamoyl imine precursors containing CCl3, CF3 and CF2H is presented. This protocol provides facile access to a series of chiral α-aryl trichloroethylamines bearing various functional groups, with moderate to high yields (40-82% yield) and high enantioselectivity (80-99% ee).

SCpRh(III)-Catalyzed Asymmetric C-H Trifluoromethylalkylation of N-Methoxybenzamides with β-Trifluoromethyl-α,β-Unsaturated Ketones

Asymmetric C-H trifluoromethylalkylation represents a novel and straightforward synthetic method for the construction of chiral CF3-containing compounds. However, the reported examples remain limited, given the challenges of reactivity and enantioselective control. Herein, we report a SCpRh(III)-catalyzed asymmetric aryl and alkenyl C-H trifluoromethylalkylation reaction with β-trifluoromethyl-α,β-unsaturated ketones. The chiral CF3-bearing adducts were obtained in moderate to good yields with high enantioselectivity (up to 81% yield and 96% ee). The reaction features mild conditions and broad substrate scope. The chiral CF3-bearing products could undergo diverse functional group transformations.

Ru-Catalyzed Asymmetric Reductive Amination of Aryl-Trifluoromethyl Ketones for Synthesis of Primary α-(Trifluoromethyl)arylmethylamines

The ruthenium-catalyzed asymmetric reductive amination of aryl-trifluoromethyl ketones affording high value primary α-(trifluoromethyl)arylmethylamines using cheap NH₄OAc as the nitrogen source and H₂ as the reductant is reported. This user-friendly and simple catalytic method tolerates various aromatic functions with electron-withdrawing or -donating substituents at the para- or meta-positions and as well challenging heteroaromatic functions, yielding primary α-(trifluoromethyl)arylmethylamines with excellent chemoselectivities, enantioselectivities, and useful yields (80-97% ee, 51-92% isolated yields). Finally, scalable and concise synthesis of key drug intermediates using this methodology is presented.

Photoredox Microfluidic Synthesis of Trifluoromethylated Amino Acids

Fluorinated amino acids are a class of highly valuable building blocks that are widely employed in biological science and pharmaceutical industry for improved stability, activity, and folding property of proteins. However, the synthetic approach has conventionally been constrained by harsh conditions and limited substrate range. We demonstrate a general synthetic protocol for photoinduced α-CF₃ amino acids using continuous flow technology that benefits from enhanced fusion and precise control of reaction time, making it potentially useful in large-scale peptide synthesis.

Fe-Catalyzed Alkylazidation of α-Trifluoromethylalkenes: An Access to Quaternary Stereocenters Containing CF3 and N3 Groups

A concise Fe-catalyzed alkylazidation of α-trifluoromethylalkenes via a C-C bond cleavage/radical addition/azidation cascade is described. This protocol features a broad substrate scope, excellent functional group compatibility, and the ability to be performed on a gram scale, thus offering a practical and step-economic approach to the synthetically useful tertiary α-trifluoromethyl azides.

Enantioselective nickel-catalyzed dicarbofunctionalization of 3,3,3-trifluoropropene

Despite paramount applications of chiral trifluoromethylated compounds in medicinal chemistry and materials science, limited strategies have been developed for catalytic asymmetric synthesis of such valuable fluorinated structures. Here, we report a nickel catalyzed enantioselective dicarbofunctionalization of inexpensive industrial chemical 3,3,3-trifluoropropene (TFP) with readily available tertiary alkyl and aryl iodides. The reaction overcomes the β-F elimination side reaction of TFP, and proceeds efficiently under mild reaction conditions. The protocol possesses advantages, such as synthetic convenience, high enantioselectivity, and excellent functional group tolerance, providing rapid and straightforward access to chiral trifluoromethylated compounds of medicinal interest.

Strategies for the catalytic asymmetric synthesis of trifluoromethylated compounds remain scarce. Here, the authors report the nickel-catalyzed enantioselective dicarbofunctionalization of 3,3,3-trifluoropropene.

Catalytic enantioselective synthesis of fluoromethylated stereocenters by asymmetric hydrogenation

Fluoromethyl groups possess specific steric and electronic properties and serve as a bioisostere of alcohol, thiol, nitro, and other functional groups, which are important in an assortment of molecular recognition processes. Herein we report a catalytic method for the asymmetric synthesis of a variety of enantioenriched products bearing fluoromethylated stereocenters with excellent yields and enantioselectivities. Various N,P-ligands were designed and applied in the hydrogenation of fluoromethylated olefins and vinyl fluorides.

Enantioselective Radical Trifluoromethylation of Benzylic C-H Bonds via Cooperative Photoredox and Copper Catalysis

The first enantioselective radical trifluoromethylation of benzylic C-H bonds has been established by a cooperative photoredox and copper catalysis system, providing straightforward access to structurally diverse benzylic trifluoromethylation products in good yields with excellent enantioselectivities under mild conditions. Our method features a broad substrate scope and excellent functional group compatibility. Merging the cooperative photoredox catalysis with copper catalysis is essential for the reaction, where the photoredox catalysis is used for the generation of benzylic radicals from alkyl arenes through a hydrogen atom transfer process and the copper catalysis is used for the enantioselective trifluoromethylation of the benzylic radicals.

Enantioselective Synthesis of α-Trifluoromethyl Amines via Biocatalytic N-H Bond Insertion with Acceptor-Acceptor Carbene Donors

The biocatalytic toolbox has recently been expanded to include enzyme-catalyzed carbene transfer reactions not occurring in Nature. Herein, we report the development of a biocatalytic strategy for the synthesis of enantioenriched α-trifluoromethyl amines through an asymmetric N–H carbene insertion reaction catalyzed by engineered variants of cytochrome c₅₅₂ from Hydrogenobacter thermophilus. Using a combination of protein and substrate engineering, this metalloprotein scaffold was redesigned to enable the synthesis of chiral α-trifluoromethyl amino esters with up to >99% yield and 95:5 er using benzyl 2-diazotrifluoropropanoate as the carbene donor. When the diazo reagent was varied, the enantioselectivity of the enzyme could be inverted to produce the opposite enantiomers of these products with up to 99.5:0.5 er. This methodology is applicable to a broad range of aryl amine substrates, and it can be leveraged to obtain chemoenzymatic access to enantioenriched β-trifluoromethyl-β-amino alcohols and halides. Computational analyses provide insights into the interplay of protein- and reagent-mediated control on the enantioselectivity of this reaction. This work introduces the first example of a biocatalytic N–H carbenoid insertion with an acceptor–acceptor carbene donor, and it offers a biocatalytic solution for the enantioselective synthesis of α-trifluoromethylated amines as valuable synthons for medicinal chemistry and the synthesis of bioactive molecules.

Regio- and enantioselective umpolung gem-difluoroallylation of hydrazones via palladium catalysis enabled by N-heterocyclic carbene ligand

The enantioselective construction of C-CF₂R (R: alkyl or fluoroalkyl) bonds has attracted the attention of synthetic chemists because of the importance of chiral fluorinated compounds in life and materials sciences. Catalytic asymmetric fluoroalkylation has mainly been realized under organocatalysis and Lewis acid catalysis, with substrates limited to carbonyl compounds. Few examples using transition-metal catalysis exist, owing to side reactions including decomposition and isomerization of fluoroalkylating reagents. Herein we report umpolung asymmetric difluoroallylation of hydrazones with 3-bromo-3,3-difluoropropene (BDFP) under palladium catalysis. Difluoroallylation products having quaternary chiral carbon centers are afforded in good yields with high α/γ- and enantioselectivities. The usefulness of the reaction products is demonstrated and an inner-sphere mechanism of the reaction is proposed. The use of chiral N-heterocyclic carbene as ligand is the key for the selectivities as well as the productivity of the reaction.

Iridium-catalyzed enantioselective addition of an N-methyl C-H bond to α-trifluoromethylstyrenes via C-H activation

The Ir-catalyzed enantioselective addition of an N-methyl C-H bond of 2-(methylamino)pyridine derivatives to α-trifluoromethylstyrenes proceeded via C-H activation to give chiral γ-branched amine derivatives having a trifluoromethyl-substituted stereocenter. It was found that a bulky and electron-withdrawing group at the 3-position of 2-(methylamino)pyridines was necessary for the present C-H addition reaction catalyzed by a cationic iridium/chiral bisphosphine complex.

Dual Nickel- and Photoredox-Catalyzed Reductive Cross-Coupling to Access Chiral Trifluoromethylated Alkanes

A dual nickel/photoredox-catalyzed enantioselective reductive cross-coupling of aryl halides with CF₃-substituted racemic alkyl electrophiles has been established. The approach accommodates a broad palette of aryl iodides and alkyl bromides to access a variety of chiral CF₃-containing compounds. The exceptionally mild conditions (visible light, ambient temperature, no strong base) and no need for Grignard reagents or stoichiometric metallic reductants provide this transformation huge potential in the application of the late-stage functionalization of complex molecules.

Diverse Synthesis of Chiral Trifluoromethylated Alkanes via Nickel-Catalyzed Asymmetric Reductive Cross-Coupling Fluoroalkylation

The trifluoromethyl group represents one of the most functional and widely used fluoroalkyl groups in drug design and screening, while the drug candidates containing chiral trifluoromethyl-bearing carbons are still few due to the lack of efficient methods for the asymmetric introduction of trifluoromethyl group into organic molecules. Herein, we described a nickel-catalyzed asymmetric trifluoroalkylation of aryl iodides, for the first time, by utilizing reductive cross-coupling in enantioselective fluoroalkylation. This novel method has demonstrated high efficiency, mild conditions, and excellent functional group tolerance, especially for substrates containing diverse pharmaceutical and bioactive molecules moieties. This strategy provided an efficient and facile way for diversity-oriented synthesis of chiral trifluoromethylated alkanes.

Strategies for the Catalytic Enantioselective Synthesis of α-Trifluoromethyl Amines

The exploitation of the α-trifluoromethylamino group as an amide surrogate in peptidomimetics and drug candidates has been on the rise. In a large number of these cases, this moiety bears stereochemistry with the stereochemical identity having important consequences on numerous molecular properties, such as the potency of the compound. Yet, the majority of stereoselective syntheses of α-CF3 amines rely on diastereoselective couplings with chiral reagents. Concurrent with the rapid expansion of fluorine into pharmaceuticals has been the development of catalytic enantioselective means of preparing α-trifluoromethyl amines. In this work, we outline the strategies that have been employed for accessing these enantioenriched amines, including normal polarity approaches and several recent developments in imine umpolung transformations.

A Role for Isatin Azomethine Imines as a Dipolarophile in Cycloaddition Reactions

An unusual [2 + 3] cycloaddition of isatin azomethine imines (AIs) and in situ generated azaoxyallyl cations has been developed. It is the first example where AIs serve as the [C,O] 2-atom synthon in organic synthesis. This work not only reveals a new role of isatin AIs in cycloaddition reaction but also provides an efficient access to unprecedented spiroheterocycle compounds.

Eosin Y-Catalyzed Visible-Light-Mediated Aerobic Transformation of Pyrazolidine-3-One Derivatives

By utilizing an underexplored reactivity of N1-substituted pyrazolidine-3-ones, we developed a visible-light-induced aerobic oxidation of N1-substituted pyrazolidine-3-one derivatives yielding the corresponding azomethine imines. The resulting azomethine imines can be further reacted with ynones in situ under copper catalyzed [3 + 2] cycloaddition reaction conditions yielding the corresponding pyrazolo[1,2-a]pyrazoles in good yields. The methodology can be extended to other 1-aryl-substituted pyrazolidinones which undergo endocyclic oxidation deriving the corresponding pyrazolones as single products.

Enantioselective synthesis of trifluoromethyl substituted cyclohexanones via an organocatalytic cascade Michael/aldol reaction

An enantioselective (92-99% ee) Michael/aldol cascade reaction between 4,4,4-trifluoroacetoacetates and α,β-unsaturated enones was established in the presence of cinchona alkaloid-based primary amines. Various β-CF3-cyclohexanones were constructed in high yields (81-99%) as a couple of separable diastereomers. This tandem reaction was sensitive to acidic co-catalysts, with a Michael/aldol condensation process favorably occurring to generate β-CF3-cyclohexenones (42-69% yield, 84-96% ee) in the presence of trifluoroacetic acid.

Enantio- and Diastereoselective Synthesis of Homoallylic α-Trifluoromethyl Amines by Catalytic Hydroalkylation of Dienes

We describe a strategy for the enantio- and diastereoselective synthesis of homoallylic α-trifluoromethyl amines by the catalytic hydroalkylation of terminal dienes. Trifluoromethyl-substituted isatin-derived azadienolate nucleophiles undergo γ-selective alkylation with a Pd-DTBM-SEGPHOS catalyst, which additionally promotes regioselective addition to the diene and delivers products in up to 86% yield, 10:1 dr, and 97.5:2.5 er.

Palladium-Catalyzed Asymmetric Allylic Fluoroalkylation/Trifluoromethylation

The first palladium-catalyzed asymmetric allylic trifluoromethylation is disclosed. The methodology evokes a fundamental principle by which the synergistic interplay of a leaving group and its subsequent activation of the nucleophilic trifluoromethyl group enabled the reaction. Allyl fluorides have been shown to be superior precursors for generation of π-allyl complexes, which lead to trifluoromethylated products with high selectivities and functional group tolerance. This study highlights the unique role of a bidentate diamidophosphite ligand class in palladium-catalyzed reactions that allow a challenging transformation to proceed.

2-Azadienes as Enamine Umpolung Synthons for the Preparation of Chiral Amines

The development of new strategies for the preparation of chiral amines is an important objective in organic synthesis. In this Synpacts, we summarize our approach for catalytically accessing nucleophilic aminoalkyl metal species from 2-azadienes, and its application in generating a number of important but elusive chiral amine scaffolds. Reductive couplings with ketones and imines afford 1,2-amino tertiary alcohols and 1,2-diamines, respectively, whereas fluoroarylations of gem-difluoro-2-azadienes deliver α-trifluoromethylated benzylic amines.

Photocatalytic reductive radical-radical coupling of N,N'-cyclicazomethine imines with difluorobromo derivatives

A visible-light-induced difluoroalkylation of N,N'-cyclicazomethine imine was successfully realized through a novel photoredox radical-radical cross-coupling reaction. This developed protocol exhibits high functional group tolerance and affords a variety of difluorinated 3-pyrazolidinone scaffolds. Extensive mechanistic investigations have been undertaken, well revealing the involvement of a reductive radical-radical coupling pathway.

F10BINOL-derived chiral phosphoric acid-catalyzed enantioselective carbonyl-ene reaction: theoretical elucidation of stereochemical outcomes

An enantioselective carbonyl-ene reaction of 1,1-disubstituted olefins with ethyl glyoxylate was accomplished using an F₁₀BINOL-derived chiral phosphoric acid of which the perfluoro-binaphthyl skeleton is beneficial not only for adopting high catalytic activity but also for creating an effective chiral environment.

An F₁₀BINOL-derived chiral phosphoric acid was shown to be an effective catalyst for an enantioselective carbonyl-ene reaction of 1,1-disubstituted olefins with ethyl glyoxylate as the common enophile. The perfluoro-binaphthyl skeleton is beneficial not only for adopting high catalytic activity but also for creating an effective chiral environment for enantioselective transformations. Indeed, the reaction afforded enantio-enriched homoallylic alcohols in high yields with high enantioselectivities. Theoretical studies identified that the multi-point C–H···O hydrogen bonds and the π interactions between the substrates and the 6-methoxy-2-naphthyl substituents at the 3,3′-positions of the F₁₀BINOL skeleton play a crucial role in determining the stereochemical outcomes. The significance of the perfluoro-binaphthyl skeleton in achieving the high enantioselectivity was also evaluated through a structural analysis of the catalysts.

Palladium-Catalyzed Synthesis of α-Trifluoromethyl Benzylic Amines via Fluoroarylation of gem-Difluoro-2-azadienes Enabled by Phosphine-Catalyzed Formation of an Azaallyl-Silver Intermediate

We report the synthesis of α-trifluoromethyl benzylic amines through the vicinal fluoroarylation of gem-difluoro-2-azadienes. Our studies indicate that XPhos plays an important role as a phase transfer catalyst that promotes the addition of AgF to the difluoroazadiene, generating an α-trifluoromethyl azaallyl-silver intermediate that we have characterized by NMR spectroscopy. This intermediate likely transmetallates to Pd, coupling several aryl iodides to deliver products in up to 90% yield. Modification of the azadiene's activating group facilitates challenging cross-couplings.

Copper-Catalyzed Highly Stereoselective Trifluoromethylation and Difluoroalkylation of Secondary Propargyl Sulfonates

It is challenging to stereoselectively introduce a trifluoromethyl group (CF₃ ) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper-catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.

Nucleophilic fluoroalkylation/cyclization route to fluorinated phthalides

Discribed in this article is a versatile and practical method for the synthesis of C3-perfluoroalkyl-substituted phthalides in a one-pot manner. Upon treatment of KF or triethylamine, 2-cyanobenzaldehyde reacted with (perfluoroalkyl)trimethylsilanes via nucleophilic addition and subsequent intramolecular cyclization to give perfluoroalkylphthalides in good yields.

Stereodivergent trifluoromethylation of N-sulfinylimines by fluoroform with either organic-superbase or organometallic-base

The first stereodivergent trifluoromethylation of N-sulfinylimines by fluoroform is reported.