Photoinduced Copper-Catalyzed Asymmetric Acylation of Allylic Phosphates with Acylsilanes

Fluoroalkylacylsilanes as Novel Ambiphilic Donor-Acceptor Carbene Precursors

ConspectusCarbenes, as highly reactive intermediates, have emerged as pivotal tools in organic synthesis, catalysis, and materials science due to their versatile reactivity and broad applicability. Among the diverse classes of carbenes, donor-acceptor carbenes (DACs) have attracted significant attention owing to their unique electronic properties and exceptional reaction selectivity. The distinctive reactivity of DACs arises from the synergistic electronic interplay between electron-withdrawing and electron-donating groups attached to the carbene center, enabling a wide array of transformations. These attributes have established DACs as indispensable building blocks for constructing complex molecular architectures and achieving precise control over chemical transformation.This Account highlights our recent advancements in the development of fluoroalkylacylsilanes as novel precursors for DACs. Under photocatalytic conditions, these fluoroalkylacylsilanes generate fluoroalkyl siloxycarbenes via a radical Brook rearrangement. The fluoroalkyl group, known for its strong electron-withdrawing properties, imparts electrophilic characteristics, while the siloxyl group stabilizes the carbene center. Together, these functionalities render fluoroalkylacylsilanes ideal candidates for the generation of DACs, providing a versatile platform for a wide range of novel transformations, including cycloadditions, bond insertions, and the construction of new molecular structures.First, we developed a visible-light-induced, organocatalyzed [2 + 1] cyclization of alkynes and trifluoroacetylsilanes, leading to the synthesis of cyclopropenols. Mechanistic studies provided compelling evidence for the involvement of triplet carbene intermediates in this reaction, demonstrating the utility of DACs in the synthesis of highly functionalized cyclic compounds. Second, we explored cyclopropanation reactions and elucidated the diastereoselective transfer of trifluoroacetylsilane-derived DACs to alkenes. Density functional theory (DFT) calculations revealed key insights into the origins of the observed diastereoselectivity, offering a molecular-level understanding of the stereochemical outcomes. Additionally, we extended the scope of our reactions to include organoboronic esters, enabling the divergent synthesis of fluoroalkyl ketones. By modulating the reactivity of the in situ-generated organoboronate complexes─formed through the reaction of DACs with organoboronic esters─we achieved selective synthesis of both fluorine-maintaining and defluorinated ketones. This transition-metal-free approach is operationally simple and compatible with a broad range of substrates, including aryl, alkenyl, and alkyl boronic esters. Beyond cyclization and C-B bond functionalization, we applied our novel DACs to C(sp2)-H functionalization reactions of 1,3-azoles. Mechanistic investigations suggest that the success of these reactions stems from the dual role of trifluoroacetylsilanes under photocatalytic conditions: they not only generate carbenes that participate in cyclopropanation but also produce biradicals that facilitate the ring-opening aromatization of the in situ-generated fused cyclopropanes.We anticipate that our work on fluoroalkylacylsilanes as ambiphilic donor-acceptor carbene precursors will lay the groundwork for further advancements in the use of functionalized acylsilanes in carbene chemistry. These developments are expected to inspire new strategies for the design of DACs and expand the utility of silanes in complex synthetic transformations, opening new avenues for the construction of intricate molecular architectures.

1,2-Acylcyanation of Styrenes by Photoinduced Nickel Catalysis to Generate Acyl Radicals from Acyl Fluorides

We report herein a photoinduced nickel-catalyzed 1,2-acylcyanation of styrenes with acyl fluorides and trimethylsilyl cyanide (TMSCN). Nickel(II) acyl complexes, formed from nickel(0) complexes and acyl fluorides, are photoexcited to generate acyl radicals via a ligand-to-metal charge transfer (LMCT) process. This transformation proceeds under mild conditions and thus can be applied to the late-stage functionalization (LSF) of natural product derivatives. Synthetic derivatizations show the utility of the products. The preparation of aza-DIPYs is also demonstrated.

Radical Brook rearrangement: past, present, and future

The Brook rearrangement has emerged as one of the most pivotal transformations in organic chemistry, with broad applications spanning organic synthesis, drug design, and materials science. Since its discovery in the 1950s, the anion-mediated Brook rearrangement has been extensively studied, laying the groundwork for the development of numerous innovative reactions. In contrast, the radical Brook rearrangement has garnered comparatively less attention, primarily due to the challenges associated with the controlled generation of alkoxyl radicals under mild conditions. However, recent advancements in visible-light catalysis and transition-metal catalysis have positioned the radical Brook rearrangement as a promising alternative synthetic strategy in organic synthesis. Despite these developments, significant limitations and challenges remain, warranting further investigation. This review provides an overview of the radical Brook rearrangement, tracing its development from past to present, and offers perspectives on future directions in the field to inspire the creation of novel synthetic tools based on this transformation.

Photoinduced Copper-Catalyzed Cross-Coupling of Acylsilanes with Heteroarenes via Bimetallic Relay

The transition metal-catalyzed direct coupling reactions involving electron-rich Fischer carbene species are largely underdeveloped and remain a big challenge. Here, a direct coupling reaction of azoles and azine N-oxides is reported with Fischer copper carbene species bearing an α-siloxy group i, which can be in situ generated from acylsilanes catalytically under photoirradiation and redox-neutral conditions. This coupling reaction between electron-rich α-siloxy Fischer Cu-carbene species with hard carbanion nucleophiles may undergo a bimetallic relay process, which is confirmed by the kinetic analysis and in situ NMR analysis. This reaction features mild conditions and remarkable heterocycle compatibility. Notably, this protocol tolerates a series of azole or azine N-oxide derivatives, including benzoxazole, benzothiazole, benzoimidazole, benzoisoxazole, oxazole, oxadiazole, triazolo[4,3-a]pyridine, purine, caffeine, pyridine N-oxide, quinoline N-oxide, pyrazine N-oxide, pyridazine N-oxide, etc. The synthetic value of this approach is demonstrated by the efficient synthesis of a histamine h4 receptor ligand and a marketed drug carbinoxamine.

Photoinduced Enantioselective Triplet Radical Reaction on Metal: Copper-Catalyzed Conjugate Addition of Acylsilanes to α,β-Unsaturated Ketones and Aldehydes

A photoinduced copper-catalyzed enantioselective conjugate addition of acylsilanes has been developed. The conjugate acylation of α,β-unsaturated ketones and aldehydes was promoted by a copper(I)/chiral NHC catalyst under visible-light irradiation for synthesizing various 2-substituted 1,4-dicarbonyl compounds in enantioenriched forms. Mechanistic studies combining experiments and quantum chemical calculations indicated a reaction mechanism involving copper-to-acyl charge transfer (i. e., metal-to-ligand charge transfer (MLCT)) excitation of an alkene-bound acylcopper complex. The MLCT excitation is followed by an electronical and geometrical change to generate a triplet β-radical-C-enolate-Cu(II)-acyl complex with an acyl radical character, which undergoes facile excited state C-C bond formation in the copper coordination sphere, affording the 1,4-conjugate addition product.

Stereoselective Synthesis of Silyl Enol Ethers with Acylsilanes and α,β-Unsaturated Ketones

Acylsilanes are emerging bench-stable reagents for the generation of electron-rich oxycarbenes that are difficult to access with unstable diazo compounds. Herein, we report a siloxycarbene-mediated stereoselective synthesis of silyl enol ethers through visible-light-induced intermolecular reactions between acylsilanes and α,β-unsaturated ketones. Both the solvent and low temperature are important for the success of the reaction. This approach features atomic economics, exclusive stereocontrol, and broad substrate scope. The synthetic potential of this methodology is demonstrated by gram-scale reaction and various downstream transformations including that requiring configuration purity of the silyl enol ethers.

Photoexcited Palladium-Catalyzed Deracemization of Allenes

The different enantiomers of specific chiral molecules frequently exhibit disparate biological, physiological, or pharmacological properties. Therefore, the efficient synthesis of single enantiomers is of particular importance not only to the pharmaceutical sector but also to other industrial sectors, such as agrochemical and fine chemical industries. Deracemization, a process during which a racemic mixture is converted into a nonracemic product with 100% atom economy and theoretical yield, is the most straightforward method to access enantioenriched molecules but a challenging task due to a decrease in entropy and microscopic reversibility. Axially chiral allenes bear a distinctive structure of two orthogonal cumulative π-systems and are acknowledged as synthetically versatile synthons in organic synthesis. The selective creation of axially chiral allenes with high optical purity under mild reaction conditions has always been a very popular and hot topic in organic synthesis but remains challenging. Herein, a photoexcited palladium-catalyzed deracemization of nonprefunctionalized disubstituted allenes is disclosed. This method provides an efficient and economical strategy to accommodate a broad scope of allenes with good enantioselectivities and yields (53 examples, up to 96% yield and 95% ee). The use of a suitable chiral palladium complex with visible light irradiation is an essential factor in achieving this transformation. A metal-to-ligand charge transfer mechanism was proposed based on control experiments and density functional theory calculations. Quantum mechanical studies implicate dual modes of asymmetric induction behind our new protocol: (1) sterically controlled stereoselective binding of one allene enantiomer under the ground-state and (2) facile, noncovalent interaction-driven excited-state isomerization toward the opposite enantiomer. The success of this newly established photochemical deracemization strategy should provide inspiration for expansion to other multisubstituted allenes and will open up a new mode for enantioselective excited-state palladium catalysis.

Desymmetrization-Addition Reaction of Cyclopropenes to Imines via Synergistic Photoredox and Cobalt Catalysis

Herein, we designed a reaction for the desymmetrization-addition of cyclopropenes to imines by leveraging the synergy between photoredox and asymmetric cobalt catalysis. This protocol facilitated the synthesis of a series of chiral functionalized cyclopropanes with high yield, enantioselectivity, and diastereoselectivity (44 examples, up to 93% yield and >99% ee). A possible reaction mechanism involving cyclopropene desymmetrization by Co-H species and imine addition by Co-alkyl species was proposed. This study provides a novel route to important chiral cyclopropanes and extends the frontier of asymmetric metallaphotoredox catalysis.

Visible photons as ideal reagents for the activation of coloured organic compounds

In recent decades, the traceless nature of visible photons has been exploited for the development of efficient synthetic strategies for the photoconversion of colourless compounds, namely, photocatalysis, chromophore activation, and the formation of an electron donor/acceptor (EDA) complex. However, the use of photoreactive coloured organic compounds is the optimal strategy to boost visible photons as ideal reagents in synthetic protocols. In view of such premises, the present review aims to provide its readership with a collection of recent photochemical strategies facilitated via direct light absorption by coloured molecules. The protocols have been classified and presented according to the nature of the intermediate/excited state achieved during the transformation.

Palladium-Catalyzed Addition of Trifluoroacetylsilanes to Alkenes and Allenes via the Cleavage of C-Si Bonds

The palladium-catalyzed addition of trifluoroacetylsilanes to alkenes and allenes via the cleavage of the C-Si bonds is reported. When alkenes are used, cyclopropanation occurs to afford cyclopropane derivatives bearing CF3 and siloxy groups with a high degree of stereoselectivity. When allenes are used, silylacylation occurs to form alkenylsilane derivatives bearing a trifluoroacetyl group at the allylic position with complete regioselectivity. Both reactions allow for highly atom-economical access to densely functionalized fluorinated organosilane derivatives using simple building blocks.

A Chiral Titanocene Complex as Regiodivergent Photoredox Catalyst: Synthetic Scope and Mechanism of Catalyst Generation

We describe a combined synthetic, spectroscopic, and computational study of a chiral titanocene complex as a regiodivergent photoredox catalyst (PRC). With Kagan's complex catCl2 either monoprotected 1,3-diols or 1,4-diols can be obtained in high selectivity from a common epoxide substrate in a regiodivergent epoxide opening depending on which enantiomer of the catalyst is employed. Due to the catalyst-controlled regioselectivity of ring opening and the broader substrate scope, the PRC with catCl2 is also a highly attractive branching point for diversity-oriented synthesis. The photochemical processes of cat(NCS)2, a suitable model for catCl2, were probed by time-correlated single-photon counting. The photoexcited complex displays a thermally activated delayed fluorescence as a result of a singlet-triplet equilibration, S1 ⇄ T1, via intersystem crossing and recrossing. Its triplet state is quenched by electron transfer to the T1 state. Computational and cyclic voltammetry studies highlight the importance of our sulfonamide additive. By bonding to sulfonamide additives, chloride abstraction from [catCl2]- is facilitated, and catalyst deactivation by coordination of the sulfonamide group is circumvented.

Visible Light Induced Copper-Catalyzed Enantioselective Deaminative Arylation of Amino Acid Derivatives Assisted by Phenol

The exploration of value-added conversions of naturally abundant amino acids has received considerable attention from the synthetic community. Compared with the well-established asymmetric decarboxylative transformation, the asymmetric deaminative transformation of amino acids still remains a formidable challenge, mainly due to the lack of effective strategies for the C-N bond activation and the potential incompatibility with chiral catalysts. Here, we disclose a photoinduced Cu-catalyzed asymmetric deaminative coupling reaction of amino acids with arylboronic acids. This new protocol provides a series of significant chiral phenylacetamides in generally good yields and excellent stereoselectivity under mild and green conditions (42-85 % yields, up to 97 % ee). Experimental investigations and theoretical calculations were performed to reveal the crucial role of additional phenols in improving catalytic efficiency and enantiocontrol.

Asymmetric Syntheses of (Z)- or (E)-β,γ-Unsaturated Ketones via Silane-Controlled Enantiodivergent Catalysis

Cu-catalyzed highly stereoselective and enantiodivergent syntheses of (Z)- or (E)-β,γ-unsaturated ketones from 1,3-butadienyl silanes are developed. The nature of the silyl group of the dienes has a significant impact on the stereo- and enantioselectivity of the reactions. Under the developed catalytic systems, the reactions of acyl fluorides with phenyldiemthylsilyl-substituted 1,3-diene gave (Z)-β,γ-unsaturated ketones bearing an α-tertiary stereogenic center with excellent enantioselectivities and high Z-selectivities, where the reactions with triisopropylsilyl-substituted 1,3-butadiene formed (E)-β,γ-unsaturated ketones with high optical purities and excellent E-selectivities. The products generated from the reactions contain three functional groups with orthogonal chemical reactivities, which can undergo a variety of transformations to afford synthetically valuable intermediates.

Photocatalytic 1,2-Phosphorus-Migrative [3 + 2] Cycloaddition of Tri(t-butyl)phosphine with Terminal Alkynes

Tri(t-butyl)phosphine and terminal alkynes undergo 1,2-phosphorus-migrative [3 + 2] cycloaddition in the presence of a proton source under photocatalytic conditions. The reaction exhibits broad functional group tolerance and affords substituted cyclic phosphonium salts, which are amenable to further derivatization by Wittig olefination. Theoretical studies suggest that the phosphorus 1,2-migration of a β-phosphonioalkyl radical proceeds through a phosphine radical cation-alkene complex as a pseudointermediate, and the two fragments in the intermediate are bound to each other through multiple noncovalent interactions.

Recent Advances in the Enantioselective Radical Reactions

The review covers research published since 2017 and is focused on enantioselective synthesis using radical reactions. It describes recent approaches to the asymmetric synthesis of chiral molecules based on the application of the metal catalysis, dual metal and organocatalysis and finally, pure organocatalysis including enzyme catalysis. This review focuses on the synthetic aspects of the methodology and tries to show which compounds can be obtained in enantiomerically enriched forms.

Bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction for construction of 5-oxazoylmethyl α-silyl alcohol

A bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction was developed. The reaction proceeded well with a broad range of N-propargylamides and acylsilanes, affording the target chiral 5-oxazoylmethyl α-silyl alcohols in up to 95% yield and 99% ee under mild conditions. Importantly, this facile protocol was available for the late-stage modification of several bioactive molecules. Based on the mechanistic study and control experiments, a possible catalytic cycle and transition state are proposed to elucidate the reaction process and enantioinduction.

A Catalytic Method for the Enantioselective Synthesis of α-Quaternary Ketones, α-Ketoesters and Aldehydes

A practical method for the efficient and enantioselective preparation of versatile ketones and aldehydes that contain an α-quaternary stereocenter is described. Reactions utilize simple carboxylic acid or ester starting materials, a monodentate chiral phosphine, and afford a variety of aryl, alkenyl, alkynyl, and alkyl-substituted ketone and aldehyde products in 25-94 % yield and 90 : 10 to >99 : 1 enantiomeric ratio. Reactions proceed by acyl substitution with in situ formed chiral allylic nucleophiles, and display selectivity and conversion dependence on a protic additive. The utility of the approach is demonstrated through several product transformations.

Electron-Rich Oxycarbenes: New Synthetic and Catalytic Applications beyond Group 6 Fischer Carbene Complexes

Oxycarbenes have emerged as useful intermediates in synthetic chemistry. Compared to the widely studied oxycarbene metal complexes bearing Group 6 metals, the synthetic and catalytic applications of oxycarbenes beyond Group 6 Fischer carbene complexes are less explored because of the difficulty in controlling their reactivity and the need to use a stoichiometric amount of a presynthesized Group 6 metal carbene complex as the starting material. This Minireview summarizes early synthetic and catalytic applications of late-transition-metal oxycarbene complexes and highlights recent advances in free oxycarbene reactions and transition-metal-catalyzed reactions involving oxycarbenes. We hope this Minireview will inspire further developments in this emerging area.

Photoinduced Cobalt-Catalyzed Desymmetrization of Dialdehydes to Access Axial Chirality

Enantioselective metallaphotoredox catalysis, which combines photoredox catalysis and asymmetric transition-metal catalysis, has become an effective approach to achieve stereoconvergence under mild conditions. Although many impressive synthetic approaches have been developed to access central chirality, the construction of axial chirality by metallaphotoredox catalysis still remains underexplored. Herein, we report two visible light-induced cobalt-catalyzed asymmetric reductive couplings of biaryl dialdehydes to synthesize axially chiral aldehydes (60 examples, up to 98% yield, >19:1 dr, and >99% ee). This protocol shows good functional group tolerance, broad substrate scope, and excellent diastereo- and enantioselectivity.

Photoinduced copper-catalyzed enantioselective coupling reactions

Copper-catalyzed enantioselective coupling has been widely investigated, which allows rapid construction of various chiral molecules. Despite important advances via polar and radical mechanisms, exploring general and practical strategies for the regio-, enantio- and diastereoselective assembly of stereogenic centers is of significant value but remains highly problematic. The integration of photocatalysis with asymmetric copper catalysis could provide appealing access to the development of new reaction pathways and structurally diverse chiral compounds, and extend the boundaries of radical chemistry. This review summarizes recent advances in photoinduced copper-catalyzed enantioselective coupling reactions, and discusses the mechanistic aspects.

Cu/SaBox-Catalyzed Photoinduced Coupling of Acylsilanes with Alkynes

The transition metal-catalyzed cross-coupling reaction with Fischer metal carbene intermediates bearing an electron-rich alkoxyl or siloxyl group remains a big challenge due to the lack of readily available corresponding carbene precursors. Herein, we report the coupling of alkynes with the Fischer-type copper carbene species bearing a α-siloxyl group, which could be in situ generated from acylsilanes catalytically under photoirradiation and redox-neutral conditions. The side-arm modified bisoxazoline (SaBox) ligands prove to be crucial for this coupling reaction, which provides the corresponding alkynyl alcohol in high yields with remarkable heterocycle tolerance and broad substrate scope.

Synthesis of Ketonylated Carbocycles via Excited-State Copper-Catalyzed Radical Carbo-Aroylation of Unactivated Alkenes

Carbocycles are core skeletons in natural and synthetic organic compounds possessing a wide diversity of important biological activities. Herein, we report the development of an excited-state copper-catalyzed radical carbo-aroylation of unactivated alkenes to synthesize ketonylated tetralins, di- and tetrahydrophenanthrenes, and cyclopentane derivatives. The reaction is operationally simple and features mild reaction conditions that tolerate a broad range of functional groups. Preliminary mechanistic studies suggest a reaction pathway beginning with photoexcitation of [CuI-BINAP]2 and followed by a single electron transfer (SET), radical aroylation of unactivated alkenes, radical cyclization, and re-aromatization, affording the desired ketonylated carbocycles.

Photocatalyzed Formal All-Carbon [3+2] Cycloaddition of Aromatic Aldehydes with Arylethynyl Silanes

Herein, we report a photoinduced TBADT-catalyzed formal all-carbon [3+2] cycloaddition of aromatic aldehydes and arylethynyl silanes, which combines acyl C-H and ortho C-H activation of aromatic aldehydes, offering a new method for constructing the indanone scaffold under mild conditions. By choosing an appropriate silane as the precursor, one can selectively retain or remove the α-silyl group of the indanone products during the reaction. Preliminary mechanistic studies point to a reaction mechanism involving a 1,5-H shift as a key step.

Photoactive Copper Complexes: Properties and Applications

Photocatalyzed and photosensitized chemical processes have seen growing interest recently and have become among the most active areas of chemical research, notably due to their applications in fields such as medicine, chemical synthesis, material science or environmental chemistry. Among all homogeneous catalytic systems reported to date, photoactive copper(I) complexes have been shown to be especially attractive, not only as alternative to noble metal complexes, and have been extensively studied and utilized recently. They are at the core of this review article which is divided into two main sections. The first one focuses on an exhaustive and comprehensive overview of the structural, photophysical and electrochemical properties of mononuclear copper(I) complexes, typical examples highlighting the most critical structural parameters and their impact on the properties being presented to enlighten future design of photoactive copper(I) complexes. The second section is devoted to their main areas of application (photoredox catalysis of organic reactions and polymerization, hydrogen production, photoreduction of carbon dioxide and dye-sensitized solar cells), illustrating their progression from early systems to the current state-of-the-art and showcasing how some limitations of photoactive copper(I) complexes can be overcome with their high versatility.

Asymmetric construction of allylicstereogenic carbon center featuring atrifluoromethyl group via enantioselective reductive fluoroalkylation

Emerging as a powerful tool for lead optimization in pharmaceutical research and development, to develop the facile, general protocols that allows the incorporation of fluorine-containing motif in drug candidates has accumulated enormous research interest in recent years. Among these important motifs, the incorporation of strategic motif CF₃ on aliphatic chain especially with the concomitant construction of trifluoromethylated alkanes bearing a CF₃-substituted stereogenic carbon, is of paramount importance. Herein, we disclose an asymmetric nickel-catalyzed reductive trifluoroalkylation of alkenyl halides for enantioselective syntheses of diverse α-trifluoromethylated allylic alkanes, offering a general protocol to access the trifluoromethyl analogue to chiral α-methylated allylic alkanes, one of the most prevalent key components among natural products and pharmaceuticals. Utilities of the method including the application of the asymmetric trifluoroalkylation on multiple biologically active complex molecules, derivatization of transformable alkenyl functionality were demonstrated, providing a facile method in the diversity-oriented syntheses of CF₃-containing chiral drugs and bioactive-molecules.

Excited-State Copper-Catalyzed [4 + 1] Annulation Reaction Enables Modular Synthesis of α,β-Unsaturated-γ-Lactams

Synthesis of α,β-unsaturated-γ-lactams continue to attract attention due to the importance of this structural motif in organic chemistry. Herein, we report the development of a visible-light-induced excited-state copper-catalyzed [4 + 1] annulation reaction for the preparation of a wide range of γ-H, -OH, and -OR-substituted α,β-unsaturated-γ-lactams using acrylamides as the 4-atom unit and aroyl chlorides as the 1-atom unit. This modular synthetic protocol features mild reaction conditions, broad substrate scope, and high functional group tolerance. The reaction is amenable to late-stage diversification of complex molecular architectures, including derivatives of marketed drugs. The products of the reaction can serve as versatile building blocks for further derivatization. Preliminary mechanistic studies suggest an inner-sphere catalytic cycle involving photoexcitation of the Cu(BINAP) catalyst, single-electron transfer, and capture of radical intermediates by copper species, followed by reductive elimination or protonation to give the desired γ-functionalized α,β-unsaturated-γ-lactams.

Shining Visible Light on Reductive Elimination: Acridine-Pd-Catalyzed Cross-Coupling of Aryl Halides with Carboxylic Acids

Despite the recent tremendous progress on transition-metal/photoredox dual catalysis in organic synthesis, single transition-metal catalysis under visible-light irradiation, which can utilize light energy more efficiently, is still underdeveloped. Herein, we report the design of photosensitizing phosphinoacridine bidentate ligands for visible-light-induced transition-metal catalysis, expecting that the electron-accepting acridine moiety would create a highly reactive electron-deficient metal center toward reductive elimination via metal-to-ligand charge transfer (MLCT). Using these ligands, we have achieved a palladium-catalyzed cross-coupling reaction of aryl halides with carboxylic acids under visible-light irradiation. Electronic tuning of the phosphinoacridine ligands not only enabled the use of a variety of aryl halides as the coupling partner, including less reactive aryl chlorides, under blue light irradiation, but also realized the employment of lower-energy green and red light for the cross-coupling. Experimental mechanistic studies have proved that the reductive elimination of aryl esters is induced by photoirradiation of phosphinoacridine-ligated arylpalladium(II) carboxylate complexes. The theoretical calculation suggests that the reductive elimination in the excited state is promoted by decreasing the electron density of the Pd center through photoinduced intramolecular electron transfer, i.e., MLCT, in the transition state owing to the electron-deficient acridine scaffold. This is a very rare example of photoinduced reductive elimination on palladium(II) complexes.

Photoexcited Chiral Copper Complex-Mediated Alkene E → Z Isomerization Enables Kinetic Resolution

While asymmetric synthesis has been established as a powerful synthetic tool for the construction of versatile enantioenriched molecules in the most efficient and practical manner, the resolution of racemates is still the most universal industrial approach to the synthesis of chiral compounds. However, the direct formation of enantiopure Z-isomers through the catalytic nonenzymatic kinetic resolution of racemic E-alkenes remains challenging. Herein, we disclose an unprecedented enantioselective E → Z isomerization mediated by a photoexcited chiral copper complex. This catalytic system enables kinetic resolution of 2-styrylpyrrolidines. This process is difficult to realize under thermal conditions. Mechanistic experiments and density functional theory (DFT) calculations revealed that different overall sensitization rates of the substrate-catalyst complex of the two enantiomers led to the observed excellent kinetic resolution efficiency. This photochemical transformation expands the potential of kinetic resolution beyond their established ground-state reactivity, furnishing a novel reaction mode for enantioselective catalysis at its excited state.

Light-driven oxidation of CH4 to C1 chemicals catalysed by an organometallic Ru complex with O2

CH₄ conversion is one of the most challenging chemical reactions due to its inertness in terms of physical and chemical properties. We have achieved photo-induced C–H bond breaking of CH₄ and successive C–O bond formation to form CH₃OH concomitant with HCHO by an organometallic Ru complex with O₂.

We have achieved aerobic transformation of methane to C₁ chemicals catalysed by a homogeneous organometallic catalyst with light energy input.

Cobalt-catalysed acyl silane directed ortho C–H functionalisation of benzoyl silanes

Acyl silanes can be engaged as weakly coordinating directing groups in cobalt catalysed C–H functionalisation reactions to prepare benzoyl silanes that are highly amenable to subsequent synthetic manipulations yet inaccessible via existing methods.