Update 1 of: Asymmetric fluorination, trifluoromethylation, and perfluoroalkylation reactions

Synthesis of (2S)-2-Chloro-2-fluororibolactone via Stereoselective Electrophilic Fluorination

A novel and efficient route for the preparation of (2S)-2-chloro-2-fluorolactone 29 is described. This approach takes advantage of a highly efficient diastereoselective electrophilic fluorination reaction (94% yield; >50:1 dr).

Synthesis of Sulfur Perfluorophenyl Compounds Using a Pentafluorobenzenesulfonyl Hypervalent Iodonium Ylide

A novel pentafluorobenzenesulfonyl hypervalent iodonium ylide 3 was designed and synthesized as a useful tool for the preparation of sulfur pentafluorophenyl compounds containing a C₆F₅S or C₆F₅SO₂ unit. Electrophilic pentafluorophenylthiolation of enamines, formal [3+2] cycloaddition reaction of nitriles and alkynes, and intramolecular S_NAr cyclization were achieved using iodonium ylide 3. The fluoro-click reaction was also demonstrated using one of the products via an intermolecular S_NAr reaction with heterocentered nucleophiles.

Forging Fluorine-Containing Quaternary Stereocenters by a Light-Driven Organocatalytic Aldol Desymmetrization Process

Reported herein is a light-triggered organocatalytic strategy for the desymmetrization of achiral 2-fluoro-substituted cyclopentane-1,3-diketones. The chemistry is based on an intermolecular aldol reaction of photochemically generated hydroxy-o-quinodimethanes and simultaneously forges two adjacent fully substituted carbon stereocenters, with one bearing a stereogenic carbon-fluorine unit. The method uses readily available substrates, a simple chiral organocatalyst, and mild reaction conditions to afford an array of highly functionalized chiral 2-fluoro-3-hydroxycyclopentanones.

Selective Synthesis of Fluorine-Containing Cyclic β-Amino Acid Scaffolds

Fluorine-containing organic molecules have generated increasing impact in drug research over the past decade. Their preparation and development of novel synthetic methods towards new types of fluorinated molecules among them of β-amino acid derivatives has received large interest. Our research group have designed various highly selective and stereocontrolled methods for the construction of fluorine-containing cyclic β-amino acid derivatives. The synthetic approaches developed for the synthesis of various pharmacologically interesting cyclic β-amino acid derivatives as monomers with multiple stereogenic centers might be valuable protocols for the access of other classes of organic compounds.

Trifluoroethoxy-Coated Phthalocyanine Catalyzes Perfluoroalkylation of Alkenes under Visible-Light Irradiation

We disclose herein the perfluoroalkylation of alkenes catalyzed by trifluoroethoxy-coated zinc phthalocyanine under irradiation of visible light. Perfluoroalkyl iodides were nicely incorporated into unsaturated substrates, including alkyne, to provide perfluoroalkyl and iodide adducts in moderate to good yields. Trifluoromethylation is also possible by trifluoromethyl iodide under the same reaction conditions. The mechanistic study is discussed.

Barbier-type anti-Diastereo- and Enantioselective Synthesis of β-Trimethylsilyl, Fluorinated Methyl, Phenylthio Homoallylic Alcohols

Catalytic Asymmetric allylation of aldehydes with functionalized allylic reagents represents an important process in synthetic organic chemistry because the resulting chiral homoallylic alcohols are valuable building blocks in diverse research fields. Despite the obvious advantages of allyl halides as allylation reagent under Barbier-type conditions, catalytic asymmetric version using functionalized allyl halides remains largely underdeveloped. Here, we addressed this issue by employing a chromium-catalysis system. The use of readily available allyl bromides with γ substitutions including trimethylsilyl, fluorinated methyl and phenylthio groups provided an efficient and convenient method to introduce those privileged functionalities into homoallylic alcohols. Good yields, high anti-diastereo- and excellent enantioselectivities were achieved under mild reaction conditions.

Enantioselective Formation of CF3-Bearing All-Carbon Quaternary Stereocenters via C-H Functionalization of Methanol: Iridium Catalyzed Allene Hydrohydroxymethylation

Using an iridium catalyst modified by PhanePhos, CF3-allenes react with methanol to form branched products of hydrohydroxymethylation as single regioisomers with excellent levels of enantiomeric enrichment. This hydrogen autotransfer process enables catalytic enantioselective formation of acyclic CF3-bearing all-carbon quaternary stereocenters in the absence of stoichiometric metals or byproducts.

Construction of β-Trifluoromethyl Enol Ether via Base-Promoted C-O Coupling and Rearrangement of Hydrogen Atom

A novel, high-efficiency and high-selectivity construction of β-trifluoromethyl enol ether via base-induced/promoted C-O coupling of trifluoromethylated vinyl chloride and phenols is presented with a broad substrate scope. The reaction mechanism, especially the significantly high selectivity, was excavated and understood via DFT calculation and is well supported by the experimental observation.

Synthesis of o-Methyl Trifluoromethyl Sulfide Substituted Benzophenones via 1,2-Difunctionalization of Aryne by Insertion into the C-C Bond

An efficient process for the preparation of valuable o-methyl trifluoromethyl sulfide substituted benzophenones has been developed. The transition-metal-free method features insertion of aryne into a C-C σ-bond under mild reaction conditions for the first time to achieve ortho-difunctionalized arenes containing a pharmaceutically important trifluoromethylthio functional group. A wide substrate scope has been demonstrated for the developed protocol.

Substrate-Controlled Product Divergence: Silver-Catalyzed Reaction of Trifluoromethyl Ketones with Terminal Alkynes

A distinct dichotomy in product distribution was initially observed in the silver-catalyzed reaction of trifluoromethyl (CF₃) ketones with terminal alkynes having two different types of electronic natures. The domino reaction smoothly proceeded almost exclusively with high stereoselectivity with terminal alkynes containing ester groups, whereas alkynylation occurred in good yield when terminal alkynes containing aryl or alkyl groups were present. The results indicated that the electronic nature of terminal alkynes can act as a switch that enables either the domino reaction or alkynylation between terminal alkynes and CF₃ ketones.

Copper-Catalyzed Asymmetric Borylation: Construction of a Stereogenic Carbon Center Bearing Both CF3 and Organoboron Functional Groups

Copper-catalyzed borylation of β-trifluoromethyl-α,β-unsaturated ketones was efficiently achieved by means of bis(pinacolato)diboron (B₂pin₂), affording the enantioenriched products in good yields with high enantioselectivities. CuI and (R,S)-Josiphos consist of the most efficient catalyst system under mild conditions. In the absence of the chiral ligand, the reactions could be performed more efficiently to form β-ketone derivatives which were directly borylated and indirectly trifluoromethylated at the β-carbon atom of the α,β-unsaturated ketone substrates. The present protocol provides a promising method to access a stereogenic carbon center bearing both CF₃ and organoboron functional groups.

Copper-Mediated Domino Cyclization/Trifluoromethylation/Deprotection with TMSCF3: Synthesis of 4-(Trifluoromethyl)pyrazoles

A copper-mediated synthesis of 4-(trifluoromethyl)pyrazoles is described. In one step from readily accessible α,β-alkynic tosylhydrazones, a remarkable domino sequence of cyclization, trifluoromethylation, and detosylation takes place to furnish the 4-CF₃ N-H pyrazole cores with good functional group compatibility. The reaction conditions are mild and convenient, at room temperature in air, using the commercially available trifluoromethyltrimethylsilane (TMSCF₃) as the CF₃ source. The method can be applied to the synthesis of a 4-CF₃ analogue of the anti-inflammatory drug celecoxib.

Phosphine-catalyzed remote α-C–H bond activation of alcohols or amines triggered by the radical trifluoromethylation of alkenes: reaction development and mechanistic insights

An efficient radical protocol for concomitant functionalization of both alkenes and remote α-C–H bonds of alcohols or amines via 1,5(6,7)-HAT was realized in a highly controlled site-selective manner.

Asymmetric synthesis of CF3-containing tetrahydroquinoline via a thiourea-catalyzed cascade reaction

The first example of the asymmetric introduction of CF₃ into the 2-position of tetrahydroquinolines was described by using β-CF₃-nitroalkene as the building block.

Copper-catalyzed regioselective 1,2-thioamidation of alkenes

An efficient method for regioselective 1,2-thioamidation of terminal alkenes, catalyzed by copper in the presence of NFSI and thiols, has been disclosed.

Computational study on NHC-catalyzed enantioselective and chemoselective fluorination of aliphatic aldehydes

A mechanistic study on NHC-catalyzed enantioselective and chemoselective fluorination of aliphatic aldehydes has been performed for the first time.

Copper-catalysed enantioselective Michael addition of malonic esters to β-trifluoromethyl-α,β-unsaturated imines

A diastereo- and enantioselective Michael addition of methyl malonate to β-trifluoromethyl unsaturated imines is presented.

1,2-Difunctionalization-type (hetero)arylation of unactivated alkenes triggered by radical addition/remote (hetero)aryl migration

A novel (hetero)arylation of unactivated alkenes has been developed via 1,4(5)-(hetero)aryl migration triggered by radical alkene azidation, trifluoromethylation, or phosphonylation.

Enantioselective electrophilic cyanation of β-keto amides catalysed by a cinchona organocatalyst

An operationally simple protocol for the enantioselective electrophilic α-cyanation of β-keto amides catalyzed by cinchona-derived catalysts has been demonstrated.

Visible-Light-Driven, Radical-Triggered Tandem Cyclization of o-Hydroxyaryl Enaminones: Facile Access to 3-CF2 /CF3-Containing Chromones

A practical and straightforward synthetic route to construct a variety of 3-CF₂/CF₃-containing chromones via photoredox catalysis was developed. This novel protocol features a visible-light-induced radical-triggered tandem cyclization.

A Stereocontrolled Protocol to Highly Functionalized Fluorinated Scaffolds through a Fluoride Opening of Oxiranes

A novel selective and substrate-dependent synthetic protocol has been developed towards the synthesis of various fluorine-containing, highly functionalized cycloalkane derivatives. The method involves the stereoselective epoxidation of some unsaturated cyclic β-amino acid derivatives as model compounds, followed by a regioselective fluoride opening of oxiranes under various conditions with Deoxofluor and XtalFluor-E reagents, thereby offering an insight into this new epoxide opening methodology with fluoride.

Mechanism of Silver-Mediated Geminal Difluorination of Styrenes with a Fluoroiodane Reagent: Insights into Lewis-Acid-Activation Model

Fluorination mediated by the cyclic hypervalent fluoroiodane reagent (1) often requires an exogenous Lewis acid. The widely accepted Lewis-acid-activation model is that a given Lewis acid binds to the oxygen atom of 1 (O-coordination) to polarize the I-O bond. Computational studies of silver-mediated geminal difluorination of styrenes with 1 reveal a new "F-coordination" model that is energetically much preferred over the commonly accepted "O-coordination" model. The calculations rationalize the regioselective formation of the geminal difluorination product.