Α-trifluoromethyl Alkenes Research Articles

Transition-Metal-Free Late-Stage Decarboxylative gem-Difluoroallylation of Primary Alkyl Acids.

A transition-metal-free late-stage decarboxylative gem-difluoroallylation of carboxylic acids with α-trifluoromethyl alkenes has been described by the use of organo-photoredox catalysis. Both primary alkyl and heteroaryl acids were readily incorporated. This approach merits feedstock materials, mild reaction conditions, and wide functionality tolerance. The synthetic utility of this approach has been highlighted by the late-stage functionalization of a variety of acid-containing natural products and drug molecules.

Zn-Mediated Fragmentation of N-Alkoxyphthalimides Enabling the Synthesis of gem-Difluoroalkenes.

Zn-mediated generation of alkoxyl radicals from N-alkoxyphthalimides emerged as an efficient approach for forming diverse and valuable alkyl radicals through β-scission or a hydrogen atom transfer process. The alkyl radical species can be further trapped by α-trifluoromethyl alkenes to construct a series of gem-difluoroalkenes.

G-C3N4-Catalyzed photochemical synthesis of trifluoromethylated gem-difluoroalkenes from α-trifluoromethyl styrenes and CF3SO2Na

Trifluoromethyl-substituted gem-difluoroalkenes were synthesized via the reaction of α-trifluoromethyl styrenes with trifluoromethyl radical derived from sodium trifluoromethylsulfinate under the visible light induced graphitic carbon nitride-mediated heterogeneous photocatalysis. The disclosed process is based on the sequential radical/ionic transformations of α-trifluoromethyl alkenes. The developed approach exploits the dual role of g-C3N4 as a photocatalyst. g-C3N4 acts as an electron acceptor for the generation of CF3 radicals and participates in the reduction of intermediate carbon-centered radical with β-elimination of fluoride anion and formation of the target products.

Organo-Photoredox Catalyzed gem-Difluoroallylation of Glycine and Glycine Residue in Peptides.

An organo-photoredox catalyzed gem-difluoroallylation of glycine with α-trifluoromethyl alkenes via direct C(sp3)-H functionalization of glycine and C-F bond activation of α-trifluoromethyl alkenes has been described. As a consequence, a broad range of gem-difluoroalkene-containing unnatural amino acids are afforded in moderate to excellent yields. This reaction exhibits multiple merits such as readily available starting materials, broad substrate scope, and mild reaction conditions. The feasibility of this reaction has been highlighted by the late-stage modification of several peptides as well as the improved in vitro antifungal activity of compound 3v toward Valsa mali compared to that with commercial azoxystrobin.

Visible light-promoted defluorinative alkylation/arylation of α-trifluoromethyl alkenes with thianthrenium salts

Defluorinative alkylation and arylation between thianthrenium salts and α-trifluoromethyl alkene to afford gem-difluoroolefins by easily recycling thianthrene under visible light irradiation and free of metal photocatalyst.

Organo-photoredox catalyzed gem-difluoroallylation of ketone-derived dihydroquinazolinones via C(sp3)-C bond and C(sp3)-F bond cleavage.

An organo-photoredox catalyzed gem-difluoroallylation of both acyclic and cyclic ketone derivatives with α-trifluoromethyl alkenes has been demonstrated, thus giving access to a diverse set of gem-difluoroalkenes in moderate to high yields. Pro-aromatic dihydroquinazolinones can be either pre-formed or in situ generated for ketone activation. This reaction is characterized by readily available starting materials, mild reaction conditions, and broad substrate scope. The feasibility of this reaction has been highlighted by the late-stage modification of several natural products and drug-like molecules as well as the in vitro antifungal activity.

Visible-light-driven selective difluoroalkylation of α-CF3 alkenes to access CF2-containing gem-difluoroalkenes and trifluoromethylalkanes

A visible-light-mediated selective difluoroalkylation of α-trifluoromethyl alkenes with difluoroalkylating reagents was developed. This protocol allowed the formation of gem-difluoroalkene difluoroacetates and trifluoromethylated difluoroacetamides.

Solvent-Controllable C-F Bond Activation for Masked Formylation of α-Trifluoromethyl Alkenes via Organo-Photoredox Catalysis.

A solvent-controllable organo-photoredox-catalyzed C-F bond activation for masked formylation of α-trifluoromethyl alkenes with low-priced 1,3-dioxolane as masked formyl radical equivalent has been described. Consequently, a diversity of masked formylated gem-difluoroalkenes and monofluoroalkenes are constructed in moderate to high yields. This approach merits readily available starting materials, mild reaction conditions, and broad substrate scope. The feasibility of this approach has been highlighted by the one-pot masked formylation/hydrolysis sequence to form γ,γ-difluoroallylic aldehydes and late-stage modification of pharmaceutical and natural product derivatives.

Visible-Light-Induced Defluorinative α-C(sp3)-H Alkylation for the Synthesis of gem-Difluoroallylated α-Trifluoromethylamines.

Herein, we describe a novel and efficient photoredox catalytic Cα radical addition/defluoroalkylation coupling reaction between α-trifluoromethyl alkenes and N-trifluoroethyl hydroxylamine. A series of gem-difluoroallylated α-trifluoromethylamines were synthesized by the Cα radical addition enabled by a 1,2-H shift of the in situ-generated N-trifluoroethyl radical. Notably, this protocol is distinguished by its mild conditions, easy operation, and excellent functional group tolerability.

Nickel-Catalyzed Enantioselective Dearomative Heck-Reductive Allylic Defluorination Reaction of Indoles.

Herein, we describe a nickel-catalyzed asymmetric dearomative aryl-difluoroallylation reaction of indoles with α-trifluoromethyl alkenes as an electrophilic coupling partner. The reaction proceeds via a cascade sequence involving dearomative Heck cyclization and reductive allylic defluorination. A series of gem-difluoroallyl substituted indolines are obtained in moderate to good yields (36-77% yield) with excellent enantioselectivity (up to 99% ee). The reaction features broad functional group tolerance, scaled-up synthesis, and late-stage diversification.

Visible-Light-Induced Monofluoroalkenylation and gem-Difluoroallylation of Inactivated C(sp3)-H Bonds via 1,5-Hydrogen Atom Transfer (HAT).

The direct monofluoroalkenylation of C(sp3)-H bonds is of great importance and quite challenging. Current methods have been restricted to the monofluoroalkenylation of activated C(sp3)-H bonds. Here, we reported the photocatalyzed C(sp3)-H monofluoroalkenylation of inactivated C(sp3)-H bonds with gem-difluoroalkenes via 1,5-hydrogen atom transfer. This process shows good functional group tolerance, such as halides (F, Cl), nitrile, sulfone, ester, and pyridine, and good γ-selectivity. Moreover, this method succeeds in the photocatalyzed gem-difluoroallylation of inactivated C(sp3)-H with α-trifluoromethyl alkenes.

Visible-light-mediated C–F bond cleavage for the synthesis of polyfluorinated compounds

Herein, we describe a novel and efficient photo-redox catalytic difluorinated ester radical addition/defluoroalkylation coupling reaction between trifluoroacetic acid derivatives and α-trifluoromethyl alkenes.

Photoredox radical/polar crossover enables C-H gem-difunctionalization of 1,3-benzodioxoles for the synthesis of monofluorocyclohexenes.

A photocatalytic C-H gem-difunctionalization of 1,3-benzodioxoles with two different alkenes for the synthesis of highly functionalized monofluorocyclohexenes is described. Using 4CzIPN as the photocatalyst, the direct single electron oxidation of 1,3-benzodioxoles allows their defluorinative coupling with α-trifluoromethyl alkenes to produce gem-difluoroalkenes in a redox-neutral radical polar crossover manifold. The C-H bond of the resultant γ,γ-difluoroallylated 1,3-benzodioxoles was further functionalized via radical addition to electron-deficient alkenes using a more oxidizing iridium photocatalyst. The capture of in situ generated carbanions by an electrophilic gem-difluoromethylene carbon and consecutive β-fluoride elimination afford monofluorocyclohexenes. The synergistic combination of multiple termination pathways of carbanions enables rapid incorporation of molecular complexity via stitching simple and readily accessible starting materials together.

Visible-light-promoted defluorinated alkylation of trifluoromethyl alkenes initiated by radical [1,2]-Brook rearrangement: facile synthesis ofgem-difluoro homoallylic alcohol derivatives

A photoinduced radical [1,2]-Brook rearrangement/defluorinated alkylation reaction of α-trifluoromethyl alkenes with α-silyl alcohols was developed for facile access togem-difluoro homoallylic alcohol derivatives.

Organophotoredox-catalyzed ring-opening gem-difluoroallylation of nonstrained cycloalkanols

Gem-difluoroalkenes exhibit widespread applications in pharmaceuticals, pesticides, and materials, and also serve as versatile building blocks for the synthesis of fluorine-containing molecules. In this report, we present a visible-light-promoted metal-free protocol for the regiospecific construction of distally unsaturated ketones bearing both versatile ketone and gem-difluoroalkene moieties. A wide range of distal gem-difluoroalkenyl ketones were readily obtained in good yields by the organophotocatalytic ring-opening defluorinative gem-difluoroallylation of nonstrained cycloalkanols with α-trifluoromethyl alkenes. This transformation exhibits broad functional group compatibility and occurs under mild, metal-free, and redox-neutral conditions. Mechanistic studies disclose that the reaction proceeds through sequential intramolecular PCET, ring opening C–C bond scission, radical-polar crossover, and E1cB fluoride elimination processes.

Nickel-Catalyzed Radical Heck-Type C(sp3)-C(sp2) Coupling Cascades Enabled by Bromoalkane-Directed 1,4-Aryl Shift: Access to Olefinated Arylalanines.

A bromoalkane-directed radical 1,4-aryl shift strategy for nickel-catalyzed reductive Heck-type C(sp3)-C(sp2) coupling cascades of α-amino-β-bromocarboxylic acid esters with α-trifluoromethyl alkenes for producing gem-difluorinated arylalanines is presented. The α-aminoalkyl radicals generated from neophyl-type aryl migration function as robust coupling partners to allow for further Giese-type addition with electron-deficient α-trifluoromethyl alkenes and vinyl sulfones, thereby realizing a new radical cascade for the simultaneous installation of an aromatic ring and olefin motif into amino acid backbones.

Photocatalytic Defluorinative Three-Component Reaction of α-Trifluoromethyl Alkenes, Alkenes, and Sodium Sulfinates: Synthesis of Monofluorocyclopentenes.

A photocatalytic three-component reaction of α-trifluoromethyl alkenes, electron-rich alkenes, and sodium sulfinates for the synthesis of gem-difluoroalkenes in a radical/polar crossover manner was developed. Due to the strong electron-withdrawing nature of the sulfonyl group, the resultant gem-difluoroalkenes can be converted into various monofluorocyclopentenes via intramolecular base-mediated SNV reactions in one pot.

Synthesis of fluorinated pyrrolizidine, indolizidine and quinolizidine derivatives

This review provides literature data dealing with the synthesis of fluorinated pyrrolizidines, indolizidines, and quinolizidines. Synthesis of trifluoromethylated derivatives requires to use of commercially available building blocks bearing pre-installed trifluoromethyl group or synthetic trifluoromethylated templates incorporating a chiral auxiliary as starting materials. On the other hand, nucleophilic or radical difluoromethylation followed by cyclization reactions using different types of stable and readily available difluoromethylating agents was established as an efficient approach for the synthesis of difluoromethylenated pyrrolizidines, indolizidines, and quinolizidines. Furthermore, a new possibility to synthesize monofluorinated quinolizidines opens the reaction of α-trifluoromethyl alkenes and dihydroisoquinoline acetic acids using visible light photocatalysis. Generality and limitations of these methods are discussed

Oxalates as Activating Groups for Tertiary Alcohols in Photoredox-Catalyzed gem-Difluoroallylation To Construct All-Carbon Quaternary Centers.

Construction of challenging and important all-carbon quaternary centers has received growing attention. Herein, with oxalates as activating groups for tertiary alcohols, we report photoredox-catalyzed gem-difluoroallylation to construct all-carbon quaternary centers enabled by efficient tertiary radical addition to α-trifluoromethyl alkenes. This transformation shows good functional group tolerance for both α-trifluoromethyl alkenes and oxalates. Moreover, this strategy is also successfully applied to the synthesis of monofluoralkenes from the corresponding electron-rich gem-difluoroalkenes and cesium tertiary alkyl oxalates under modified conditions.

Iron-Catalyzed Allylic Defluorinative Ketone Olefin Coupling.

In this protocol, we demonstrate our discovery that iron is able to efficiently catalyze the reductive allylic defluorinative ketyl olefin coupling reaction between α-trifluoromethyl alkenes and unactivated ketones. This operationally simple cross-electrophile reaction circumvents the use of pre-generated organometallics and allows for the synthesis of diverse functional-group-rich tertiary gem-difluorohomoallylic alcohols through a polarity-reversed strategy. Preliminary mechanistic studies support a mechanism that proceeds through a ketyl formation/olefin insertion/β-fluoro elimination sequence.