Cross-dehydrogenative Coupling Reaction Research Articles

Open frame-like Co-Fe oxides superstructures for highly efficient cross-dehydrogenative coupling reaction of N-phenyltetrahydroisoquinoline under mild conditions

An open frame-like Co-Fe oxides catalyst has been successfully prepared using a time-controlled strategy. Benefiting from the unique open frame-like superstructure and synergistic bimetallic composition, this novel catalyst exhibits excellent catalytic activity (up to 91 % isolated yield) and substrate suitability for Cross-Dehydrogenative Coupling reaction (CDC) of N-phenyltetrahydroisoquinolines and nitroalkanes using oxygen as the oxidant under mild reaction conditions. And after several runs, the reused catalyst still maintains great stability. This may attributed to the interaction between Fe and Co. In addition, through the radical trapping experiments, we found that O2·− species play an important role in the cross-dehydrogenative coupling reaction.

Synthesis of α-Carbonyl-α'-sulfenyl Sulfoxonium Ylides in Water at Room Temperature.

An efficient synthesis of α-carbonyl-α'-sulfenyl sulfoxonium ylides through a KIO3-promoted cross-dehydrogenative coupling reaction of aryl thiols and α-carbonyl sulfoxonium ylides in an aqueous medium at room temperature has been described. The α-carbonyl sulfoxonium ylides and aryl thiols adorned with various functional groups were well-tolerated and afforded moderate to high yields of α-carbonyl-α'-sulfenyl sulfoxonium ylide derivatives. Finally, by converting synthesized ylide 3a into other valuable compounds, we demonstrated the practicality of this synthetic method.

RuII-Catalyzed C-H Activated Diverse Cyclization with Transformation of Substrate-DG to Functional Groups: Synthesis of Functionalized Indoles and Indenones.

We present an elegant and efficient method for Ru(II)-catalyzed C-H activation, followed by a diverse range of intermolecular cross-dehydrogenative coupling reactions. This process is facilitated by an intrinsic directing group (DG) and includes the in situ transformation of the DG into common and useful functional groups. Notably, this method avoids the installation and deinstallation of the directing group. Our approach enables the selective functionalization of benzimidate, coupled with the cyclization of o-alkynyl-aniline, resulting in the high-yield synthesis of diverse compounds such as indoles, and indenones. The sequential formation of C-N, C-C, and C-O bonds, followed by hydrolysis, underscores the versatile in situ transformation of the directing group. This work not only broadens the synthetic toolbox for constructing complex heterocyclic structures but also highlights the potential for sustainable and selective synthesis of valuable compounds.

Photoinduced HCl-Mediated Cross-Dehydrogenative Coupling of Quinolines with Alcohols and Ethers.

Via light irradiation, cross-dehydrogenative coupling of quinolines with alcohols and ethers was achieved under mild conditions. A stoichiometric amount of HCl and room temperature were necessary to promote the reaction. A green Minisci-type cross-dehydrogenative coupling reaction was performed without an oxidant or a transition-metal catalyst.

Anchoring Catalytic Metal Nodes within a Single-Crystalline Pyrazolate Metal-Organic Framework for Efficient Heterogeneous Catalysis.

The synthesis of single-crystalline and robust pyrazolate metal-organic frameworks (Pz-MOFs) capable of facilitating challenging organic transformations is fundamentally significant in catalysis. Here we demonstrate a metal-node-based catalytic site anchoring strategy by synthesizing a single-crystalline and robust Pz-MOF (PCN-1004). PCN-1004 features one-dimensional (1D) copper-Pz chains interconnected by well-organized ligands, forming a porous three-dimensional (3D) network with two types of 1D open channels. Notably, PCN-1004 displays exceptional stability in aqueous solutions across a broad pH range (1 to 14), attributed to the robust copper-Pz coordination bonds. Significantly, PCN-1004 functions as an outstanding catalyst in cross dehydrogenative coupling reactions for constructing C-O/C-S bonds, even in the absence of directing groups, achieving yields of up to ~99%, with long cycle lives and high substrate compatibility. PCN-1004 outperforms all previously reported porphyrin-based homogeneous and heterogeneous catalysts. Control experiments and computations elucidate the pivotal catalytic role of the copper-Pz chains and reveal a free radical pathway for the reaction. This work not only demonstrates the successful implementation of a metal-node-based catalytic site anchoring strategy for the efficient catalysis of challenging organic transformations but also highlights the synergistic effect of a robust framework, 1D open channels, and active sites in enhancing catalytic efficiency within MOFs.

Anchoring Catalytic Metal Nodes within a Single‐Crystalline Pyrazolate Metal‐Organic Framework for Efficient Heterogeneous Catalysis

The synthesis of single‐crystalline and robust pyrazolate metal‐organic frameworks (Pz‐MOFs) capable of facilitating challenging organic transformations is fundamentally significant in catalysis. Here we demonstrate a metal‐node‐based catalytic site anchoring strategy by synthesizing a single‐crystalline and robust Pz‐MOF (PCN‐1004). PCN‐1004 features one‐dimensional (1D) copper‐Pz chains interconnected by well‐organized ligands, forming a porous three‐dimensional (3D) network with two types of 1D open channels. Notably, PCN‐1004 displays exceptional stability in aqueous solutions across a broad pH range (1 to 14), attributed to the robust copper‐Pz coordination bonds. Significantly, PCN‐1004 functions as an outstanding catalyst in cross dehydrogenative coupling reactions for constructing C‐O/C‐S bonds, even in the absence of directing groups, achieving yields of up to ~99%, with long cycle lives and high substrate compatibility. PCN‐1004 outperforms all previously reported porphyrin‐based homogeneous and heterogeneous catalysts. Control experiments and computations elucidate the pivotal catalytic role of the copper‐Pz chains and reveal a free radical pathway for the reaction. This work not only demonstrates the successful implementation of a metal‐node‐based catalytic site anchoring strategy for the efficient catalysis of challenging organic transformations but also highlights the synergistic effect of a robust framework, 1D open channels, and active sites in enhancing catalytic efficiency within MOFs.

Hollow CoFe Oxide Prisms for Cross-Dehydrogenative Coupling Reactions of 1,2,3,4-Tetrahydroisoquinolines under Mild Conditions.

A three-dimensional hollow CoFe oxide prism catalyst was successfully prepared via a self-template strategy. This bimetallic oxide catalyst demonstrated excellent catalytic activity in cross-dehydrogenative coupling reactions of 1,2,3,4-tetrahydroisoquinolines under mild conditions compared to its monometallic oxide counterparts. A preliminary mechanistic investigation showed the involvement of reactive oxygen species, produced from molecular O2 by the active bimetallic oxide catalyst in the catalytic cycle.

An environment-friendly phosphotungstic acid catalyzed cross-dehydrogenative coupling reaction to synthesize 9-substituted-9H-xanthenes with photoelectrochemical performance

An environment-friendly phosphotungstic acid catalyzed cross-dehydrogenative coupling reaction for the synthesis of 9-substituted-9H-xanthenes under oxygen and solvent-free conditions have been developed. The economic and practical reaction exhibited good substrate applicability tolerance, various 9-substituted-9H-xanthenes were synthesized in moderate to excellent yields by tuning the ratio of xanthenes and ketones (22 examples, up to 99% yield). By testing the photoelectrochemical performance, some of the xanthene derivatives (10c, 12c, 13c and 2d) showed stable photocurrent value, especially 2d had better cathode photocurrent value and application potential.

Investigation of heavy atom effects and pH sensitivity on the photocatalytic cross-dehydrogenative coupling reaction of halogenated fluorescein dyes

Fluorescein halogenated dyes are excellent photocatalysts for cross-dehydrogenation-coupled (CDC) reaction. In this paper, seven different halo-fluorescein dyes were selected to investigate the influence of heavy halogen atoms and proton concentrations on halo-fluoresceins for photocatalytic CDC reaction. The results showed that the heavy atoms directly affected intersystem crossing (ISC), which could act as a gatekeeper in the photoredox cycle and also affect photoinduced electron transfer (PET) process. Thus, the photocatalytic performance clearly increased in the following order: fluorescein FL (0.11 mol L−1•h−1)＜dibromo-fluorescein FL-2Br (0.19 mol L−1•h−1)＜diiodo-fluorescein FL-2I (0.29 mol L−1•h−1)＜tetrabromo-fluorescein FL-4Br (0.375 mol L−1•h−1)＜tetrabromo-tetrachloro-fluorescein FL-4Br–4Cl (0.53 mol L−1•h−1)＜tetraiodo-fluorescein FL-4I (0.58 mol L−1•h−1)＜ tetraiodo-tetrachloro-fluorescein FL-4I–4Cl (0.74 mol L−1•h−1). Furthermore, the visible light absorption of halogenated fluorescein dyes varied significantly with pH, thereby affecting their photocatalytic activity of CDC reaction. The dianionic FL-4I–4Cl could fully absorb light energy and exhibit excellent photocatalytic performance under mildly alkaline conditions (pH = 8), achieving a CDC reaction conversion rate of 99.92 %, which was 2.6 times higher than that of the lactone form of FL-4I–4Cl under acidic conditions (pH = 2).

Porous polyselenoviologen with long-lived charge separated states and highly cyclic stability for heterogeneous photocatalytic reaction and hydrogen production

A highly stable heterogeneous photocatalyst, porous polyselenoviologen (POP-SeV2+), was successfully synthesized via SN2 reaction. Compared to the monomer, POP-SeV2+ exhibited strong visible-light absorption, enhanced electron acceptor property, and prolonged lifetime of radical cations. Simultaneously, the femtosecond transient absorption (fs-TA) illustrated that the formation of tetrahedral multi-cationic structure is conducive to the rapid generation of molecular excited states and extending the duration of charge-separated states. Due to its remarkable characteristics, the POP-SeV2+ was employed as a photocatalyst for visible-light-induced cross-dehydrogenative coupling (CDC) reactions with a highly efficient yield (82 %). Additionally, its utilization was further extended to the hydrogen generation, demonstrating remarkable outcomes such as a high rate of H2 generation (300 μmol·h−1·g−1), and an apparent quantum yield (0.13 %). Notably, POP-SeV2+ displayed great stability and reusability in the photocatalytic process, which can distinguish it from those soluble SeV2+-based photocatalysts. The catalytic efficiency of POP-SeV2+ remained virtually unaffected even after undergoing several recycling cycles, which not only achieved the complete heterogeneous photocatalysis of SeV2+-based systems for the first time but also provided a new strategy to improve the application effect of viologen derivatives in solar energy conversion and utilization.

Tunable multicolor supramolecular assemblies based on phosphorescence cascade energy transfer for photocatalytic organic conversion and anti-counterfeiting

Making full use of the captured energy by phosphorescence light-harvesting systems (PLHSs) and the tunable photoluminescence in energy transfer process to realize the multiple applications is still the challenge of PLHSs research. In this study, we have successfully constructed a highly effective PLHS with tunable multicolor luminescence and efficient conversion of photosensitizer types, which can further be used in photocatalytic organic conversion, information anti-counterfeiting and storage. The supramolecular polymer of BDBP-CB[8], which is generated by cucurbit[8]uril (CB[8]) and 4-(4-bromophenyl)-pyridine derivative (BDBP), realizes a phosphorescence emission and a change in luminescence color. Notably, white light emission was achieved and the logic gate systems were constructed utilizing the application of adjustable luminescence color. More interestingly, PLHS can be constructed by employing BDBP-CB[8] as energy donors, Sulforhodamine 101 (SR101) and Cyanine5 (Cy5) as energy acceptors, which results in a remarkably tunable multicolor photoluminescence to achieve the information storage. Furthermore, we have also found that BDBP-CB[8] can serve as type II photosensitizer for the effective production of singlet oxygen (1O2) during the photooxidation process of styrene in aqueous environments, attaining a remarkable output rate reaching as high as 89 %. Particularly, compared with 1O2 produced by type II photosensitizer BDBP-CB[8], the construction of PLHS can effectively convert type II photosensitizer to type I photosensitizer and efficiently generate superoxide anion radical (O2•−), which can be used for photocatalytic cross-dehydrogenative coupling (CDC) reaction in the aqueous solution with a yield of 90 %. Thus, we have created a PLHS that not only achieves tunable multicolor emission for information anti-counterfeiting and storage, but also realizes the conversion of reactive oxygen species (ROS) for different types photocatalytic oxidation reactions.

RhRu Bimetallic Oxide Cluster Catalysts for Cross-Dehydrogenative Coupling of Arenes and Carboxylic Acids.

Noble-metal-based bimetallic oxide clusters are promising novel catalysts. In this study, we developed carbon-supported RhRu bimetallic oxide clusters (RhRuOx/C) with a mean diameter of 1.2 nm, which showed remarkable catalytic activity for the cross-dehydrogenative coupling (CDC) of arenes and carboxylic acids with O2 as the sole oxidant. RhRu bimetallic oxide cluster formation was confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy and synchrotron X-ray absorption spectroscopy. Kinetic isotope and substituent effects indicated that arene C-H bond cleavage was the rate-determining step and proceeded via electrophilic concerted metalation-deprotonation mechanism, with a carboxylate as an internal base. Density functional theory calculations supported the proposed mechanism and indicated that the active center for C-H bond activation was Rh(V) rather than Rh(III), while Ru enhanced the electrophilicity of the Rh(V) site by decreasing the negative charge of the surrounding oxygen atoms. Electron-rich arenes showed relatively high reactivity for the RhRuOx/C-catalyzed CDC reaction, and both aliphatic and aromatic carboxylic acids were applicable to the reaction. The RhRuOx/C catalyst is promising for the CDC reaction of arenes and carboxylic acids to produce aryl esters. This work promotes the development of noble-metal-based bimetallic oxide clusters for C-H bond activation reactions.

Phenotellurazine redox catalysts: elements of design for radical cross-dehydrogenative coupling reactions.

Redox active phenotellurazine catalysts have been recently utilized in two different cross-dehydrogenative coupling reactions. In this study, we revisit the design of the phenotellurazine redox catalysts. In particular, we investigate the level of cooperativity between the Te- and N-centers, the effect of secondary versus tertiary N-centers, the effect of heterocyclic versus non-heterocyclic structures, and the effect of substitution patterns on the redox catalytic activity.

Electricity-driven enantioselective cross-dehydrogenative coupling of two C(sp3)-H bonds enabled by organocatalysis

An efficient and scalable electrochemical asymmetric protocol with metal-free catalysts and even without additional oxidants for the cross-dehydrogenative coupling reaction (CDC) of two C(sp3)-H bonds is reported. A series of aldehydes including natural products and various substrates containing C(sp3)-H bonds including xanthenes, acridines, cycloheptatrienes and even diarylmethane have been shown to undergo asymmetric CDC to afford a series of carbon-carbon bond coupling products with up to 94% yield and 98% ee. Mechanistic studies such as radical clock experiment suggest that the reaction proceeds via nucleophilic attack by enamine under electrochemical conditions.

A Robust Pyrazolate Metal-Organic Framework for Efficient Catalysis of Dehydrogenative C-O Cross Coupling Reaction.

Construction of robust heterogeneous catalysts with atomic precision is a long-sought pursuit in the catalysis field due to its fundamental significance in taming chemical transformations. Herein, we present the synthesis of a single-crystalline pyrazolate metal-organic framework (MOF) named PCN-300, bearing a lamellar structure with two distinct Cu centers and one-dimensional (1D) open channels when stacked. PCN-300 exhibits exceptional stability in aqueous solutions across a broad pH range from 1 to 14. In contrast, its monomeric counterpart assembled through hydrogen bonding displays limited stability, emphasizing the role of Cu-pyrazolate coordination bonds in framework robustness. Remarkably, the synergy of the 1D open channels, excellent stability, and the active Cu-porphyrin sites endows PCN-300 with outstanding catalytic activity in the cross dehydrogenative coupling reaction to form the C-O bond without the "compulsory" ortho-position directing groups (yields up to 96%), outperforming homogeneous Cu-porphyrin catalysts. Moreover, PCN-300 exhibits superior recyclability and compatibility with various phenol substrates. Control experiments reveal the synergy between the Cu-porphyrin center and framework in PCN-300 and computations unveil the free radical pathway of the reaction. This study highlights the power of robust pyrazolate MOFs in directly activating C-H bonds and catalyzing challenging chemical transformations in an environmentally friendly manner.

Salicylaldehyde-Cobalt(II)-Catalyzed C-H Alkoxylation of Indoles with Secondary Alcohols.

A straight and efficient protocol for the synthesis of hindered indole-ethers via C-H alkoxylation of indoles was developed by a cobalt-catalyzed cross-dehydrogenative coupling reaction with secondary alcohols. The selection of the salicylaldehyde-Co(II) catalyst enables the reaction to proceed under conditions without acid or base addition in the presence of limited alcohols. The protocol has broad substrate scope for both indole and secondary alcohols and exhibits good functional tolerance. The synthetic applications are proven by gram-scale reaction and further diversification of the product. Preliminary mechanistic investigations indicate that the activation of C-H bonds is not the rate-determining step of the reaction.

Aromatic Amine Catalysts for the O2-Mediated Cross-Dehydrogenative Phenothiazination Reaction?

AbstractMetal-free aromatic amines have been utilized recently as redox-active catalysts in various oxidative coupling reactions. In this study, we investigated a series of aromatic amines and their potential redox catalytic activity, in particular compared to our previously reported amino-Te(II) catalysts. The O2-mediated cross-dehydrogenative phenothiazination of phenols was utilized as a benchmark test reaction, as well as the O2-mediated cross-dehydrogenative coupling of indoles. We thus identified a proton sponge as an effective aromatic amine redox catalyst. It was moreover found that although the proton sponge displays clear catalytic activity, it is generally less active than previously reported phenotellurazine catalysts. The insights provided by this study should guide future research efforts for the development of innovative redox-catalyzed cross-dehydrogenative coupling reactions.

Rose‐Bengal‐Photocatalyzed Cross‐Dehydrogenative Coupling Reactions under Visible Light

AbstractOver the past few years, organic chemistry has used the organic dye rose bengal‘s ability to absorb visible light. In present‐day research, the innovation of environmentally friendly processes for carbon‐carbon/carbon‐heteroatoms (Nitrogen, Oxygen, Sulphur, and Phosphorus) bond formation has great importance. The photocatalyzed cross‐dehydrogenative coupling (CDC) reactions using rose bengal (RB) is a promising technique for creating carbon‐carbon/carbon‐heteroatom bonds directly from readily available compounds. Our review focuses on the current advancement in rose bengal that uses photocatalyzed carbon‐carbon/carbon‐heteroatom bond‐making reactions to synthesize various important organic molecules via CDC reactions.

Pd-Catalyzed Oxidative Functionalization of Alkenes, Arenes, and 1,3-Dienes Using Molecular Oxygen as the Terminal Oxidant

AbstractThis Account presents palladium-complex-catalyzed oxidative couplings mainly developed by the author’s group, including oxidative amination and silylation of terminal alkenes, direct oxidative arylation of aromatic compounds, and oxidative difunctionalization of 1,3-dienes. The catalytic cycles in these representative reactions feature re-oxidation of the palladium species with molecular oxygen as the terminal oxidant. Varying the combination of palladium catalyst and re-oxidant enables the formation of a variety of bonds through dehydrogenative cross-coupling reactions.1 Introduction2 Oxidative Amination of Terminal Alkenes3 Direct Oxidative Arylation of Aromatic Compounds4 Oxidative Silylation of Terminal Alkenes5 Oxidative Difunctionalization of 1,3-Dienes6 Conclusions and Perspectives

Enones from aldehydes and alkenes by carbene-catalyzed dehydrogenative couplings

Enones are widely explored in synthetic chemistry as fundamental building blocks for a wide range of reactions and exhibit intriguing biological activities that are pivotal for drug discovery. The development of synthetic strategies for highly efficient preparation of enones thereby receives intense attention, in particular through the transition metal-catalyzed coupling reactions. Here, we describe a carbene-catalyzed cross dehydrogenative coupling (CDC) reaction that enables effective assembly of simple aldehydes and alkenes to afford a diverse set of enone derivatives. Mechanistically, the in situ generated aryl radical is pivotal to “activate” the alkene by forming an allyl radical through intermolecular hydrogen atom transfer (HAT) pathway and thus forging the carbon-carbon bond formation with aldehyde as the acyl synthon. Notably, our method represents the first example on the enone synthesis through coupling of “non-functionalized” aldehydes and alkenes as coupling partners, and offers a distinct organocatalytic pathway to the transition metal-catalyzed coupling transformations.