Transition-Metal-Free Aryl–Aryl Cross-Coupling: C−H Arylation of 2-Naphthols with Diaryliodonium Salts

Transition-metal-free regioselecitive C−H arylation of 2-naphthols with diaryliodonium salts has been developed. The reaction proceeds under very simple experimental conditions and affords a range of products with various substitution patterns. The method allows for the incorporation of electron-deficient aryls, which complements well currently existing metal-free aryl–aryl cross-couplings of phenols that have been so far restricted to the introduction of electron-rich aryl moieties. The mechanism of the reaction was studied by means of DFT calculations, demonstrating that the C−C bond formation occurs via a dearomatization of 2-naphthol substrate, followed by a subsequent rearomatization by tautomerization. The computations show that the use of a low polarity solvent and an insoluble inorganic base is key to securing the high selectivity of the C−C coupling over a competing C−O arylation pathway, by preventing the incipient deprotonation of 2-naphthol.     

Efficient and Recyclable RuCl3 ⋅ 3H2O Catalyst Modified with Ionic Diphosphine for the Alkoxycarbonylation of Aryl Halides

A series of ionic (mono-/di-)phosphines ( L2 , L4 , and L6 ) with structural similarity and their corresponding neutral counterparts ( L1 , L3 , and L5 ) were applied to modulate the catalytic performance of RuCl₃ ⋅ 3H₂O. With the involvement of the ionic diphosphine ( L4 ), in which the two phosphino-fragments were linked by butylene group, RuCl₃ ⋅ 3H₂O with advantages of low cost, robustness, and good availability was found to be an efficient and recyclable catalyst for the alkoxycarbonylation of aryl halides. The L4 -based RuCl₃ ⋅ 3H₂O system corresponded to the best conversion of PhI (96 %) along with 99 % selectivity to the target product of methyl benzoate as well as the good generality to alkoxycarbonylation of different aryl halides (ArX, X=I and Br) with alcohols MeOH, EtOH, i-PrOH and n-BuOH. The electronic and steric effects of the applied phosphines, which were analyzed by the ³¹P NMR for ¹J³¹_P-⁷⁷_Se¹J measurement and single-crystal X-ray diffraction, were carefully co-related to the performance RuCl₃ ⋅ 3H₂O catalyst. In addition, the L4 -based RuCl₃ ⋅ 3H₂O system could be recycled successfully for at least eight runs in the ionic liquid [Bmim]PF₆.     

Palladium-Catalyzed Benzylic C(sp3)−H Carbonylative Arylation with Aryl Bromides

A novel, selective and high-yielding palladium-catalyzed carbonylative arylation of a variety of weakly acidic (pK_a 25–35 in DMSO) benzylic and heterobenzylic C(sp³)−H bonds with aryl bromides has been achieved. This system is applicable to a range of pro-nucleophiles for access to sterically and electronically diverse α-aryl or α,α-diaryl ketones, which are ubiquitous substructures in biologically active compounds. The Josiphos SL-J001-1-based palladium catalyst was identified as the most efficient and selective, enabling carbonylative arylation with aryl bromides under 1 atm CO to provide the ketone products without the formation of direct coupling byproducts. Additionally, (Josiphos)Pd(CO)₂ was identified as the catalyst resting state. A kinetic study suggests that the oxidative addition of aryl bromides is the turnover-limiting step. Key catalytic intermediates were also isolated.     

Photoinduced Heterogeneous C−H Arylation by a Reusable Hybrid Copper Catalyst

Heterogeneous copper catalysis enabled photoinduced C−H arylations under exceedingly mild conditions at room temperature. The versatile hybrid copper catalyst provided step-economical access to arylated heteroarenes, terpenes and alkaloid natural products with various aryl halides. The hybrid copper catalyst could be reused without significant loss of catalytic efficacy. Detailed studies in terms of TEM, HRTEM and XPS analysis of the hybrid copper catalyst, among others, supported its outstanding stability and reusability.     

A Dual Palladium and Copper Hydride Catalyzed Approach for Alkyl–Aryl Cross-Coupling of Aryl Halides and Olefins

We report an efficient means of sp²–sp³ cross coupling for a variety of terminal monosubstituted olefins with aryl electrophiles using Pd and CuH catalysis. In addition to its applicability to a range of aryl bromide substrates, this process was also suitable for electron-deficient aryl chlorides, furnishing higher yields than the corresponding aryl bromides in these cases. The optimized protocol does not require the use of a glovebox and employs air-stable Cu and Pd complexes as precatalysts. A reaction on 10 mmol scale further highlighted the practical utility of this protocol. Employing a similar protocol, a series of cyclic alkenes were also examined. Cyclopentene was shown to undergo efficient coupling under these conditions. Lastly, deuterium-labeling studies indicate that deuterium scrambling does not take place in this sp²-sp³ cross coupling, implying that β-hydride elimination is not a significant process in this transformation.     

Triton B–Mediated Efficient and Convenient Alkoxylation of Activated Aryl and Heteroaryl Halides

A simple and convenient one-pot synthesis of aryl alkyl ethers by the alkoxylation of aryl halides with alcohol in the presence of Triton B as a base is described. The procedure is applicable for a variety of aryl and heteroaryl halides, and yields are very good. The use of a nonmetallic base and solvent-free conditions are important features of the reaction.     

meta-C−H Arylation and Alkylation of Benzylsulfonamide Enabled by a Palladium(II)/Isoquinoline Catalyst

Palladium(II)-catalyzed meta-C−H arylation and alkylation of benzylsulfonamide using 2-carbomethoxynorbornene (NBE-CO₂Me) as a transient mediator are realized by using a newly developed electron-deficient directing group and isoquinoline as a ligand. This protocol features broad substrate scope and excellent functional-group tolerance. The meta-substituted benyzlsulfonamides can be readily transformed into sodium sulfonates, sulfonate esters, and sulfonamides, as well as styrenes by Julia-type olefination. The unique impact of the isoquinoline ligand underscores the importance of subtle matching between ligands and the directing groups.     

meta-Selective C−H Arylation of Fluoroarenes and Simple Arenes

Fluorine is known to promote ortho-C−H metalation. Based upon this reactivity, we employed an activated norbornene that traps the ortho-palladation intermediate and is then relayed to the meta position, leading to meta-selective C−H arylation of fluoroarenes. Deuterium experiment suggests that this meta-arylation is initiated by ortho C−H activation and the catalytic cycle is terminated by C-2 protonation. A dual-ligand system is crucial for the observed high reactivity and site selectivity. Applying this approach to simple benzene or other arenes also affords arylation products with good yield and site selectivity.     

Regioselective Synthesis of Polycyclic and Heptagon-embedded Aromatic Compounds through a Versatile π-Extension of Aryl Halides

A versatile π-extension reaction was developed based on the three-component cross-coupling of aryl halides, 2-haloarylcarboxylic acids, and norbornadiene. The transformation is driven by the direction and subsequent decarboxylation of the carboxyl group, while norbornadiene serves as an ortho-C−H activator and ethylene synthon via a retro-Diels–Alder reaction. Comprehensive DFT calculations were performed to account for the catalytic intermediates.     

The Role of Catalyst Formation–Deactivation Processes and Evidence for a Nonlinear Mechanism in the Mizoroki–Heck Reaction with Aryl Chlorides

Kinetics and Catalysis - An operando kinetic study was made of the Mizoroki–Heck reaction with low-reactive aryl chlorides using the most practically attractive “ligand-free”...     

Suzuki Coupling of Cyclopropylboronic Acid With Aryl Halides Catalyzed by a Palladium–Tetraphosphine Complex

The tetraphosphine all‐cis‐1,2,3,4‐tetrakis(diphenylphosphinomethyl)cyclopentane (Tedicyp) in combination with [Pd(C₃H₅)Cl]₂ affords a very efficient catalyst for the coupling of cyclopropylboronic acid with aryl bromides and aryl chlorides. Higher reactions rates were observed with aryl bromides than with aryl chlorides; however, even in the presence of 1–0.4% of catalyst, a few aryl chlorides gave the coupling products in good yields. A wide variety of substituents such as alkyl, methoxy, trifluoromethyl, acetyl, benzoyl, formyl, carboxylate, nitro, and nitrile on the aryl halides are tolerated. The coupling reaction of sterically very congested aryl bromides such as bromomesitylene or 2,4,6‐triisopropylbromobenzene also proceeds in good yields.     

Direct Arylation of Benzene with Aryl Bromides using High‐Temperature/High‐Pressure Process Windows: Expanding the Scope of C?H Activation Chemistry

A detailed investigation on the direct arylation of benzene with aryl bromides by using first‐row transition metals under high‐temperature/high‐pressure (high‐T/p) conditions is described. By employing a parallel reactor platform for rapid reaction screening and discovery at elevated temperatures, various metal/ligand/base combinations were evaluated for their ability to enable biaryl formation through C? H activation. The combination of cobalt(III) acetylacetonate and lithium bis(trimethylsilyl)amide was subjected to further process intensification at 200 °C (15 bar), allowing a significant reduction of the catalyst/base loading and a dramatic increase in catalytic efficiency (turnover frequency) by a factor of 1000 compared to traditional protocols. The high‐throughput screening additionally identified novel nickel‐ and copper‐based metal/ligand combinations that favored an amination pathway competing with C? H activation, with the addition of ligands, such as 1,10‐phenanthroline, having a profound influence on the selectivity. In addition to metal‐based catalysts, high‐T/p process windows were also successfully applied to transition‐metal‐free systems, utilizing 1,10‐phenanthroline as organocatalyst.     

Palladium/PC-Phos-Catalyzed Asymmetric Heck/Tsuji–Trost Reactions of Amino-Tethered 1,3-Cyclohexadiene with Aryl and Alkenyl Halides

Chiral perhydroindoles are found in a number of natural products and biologically active compounds. Therefore, the development of new asymmetric methodology for rapid access to this core is of high importance. Herein, we reported a highly regio- and diastereo-selective palladium/PC-Phos-catalyzed asymmetric Heck/Tsuji–Trost reactions of readily available amino tethered 1,3-cyclohexadienes with aryl and alkenyl halides, delivering various functionalized chiral hexahydroindoles in good yields with high enantioselectivity. The application of this reaction to the concise synthesis of (−)-α-Lycorane was demonstrated. DFT computation results indicate that the difference in ΔE_dis of two migration insertion transition states determines the enantioselectivity of the reaction.     

Photo-Driven Direct C−H Arylation of Quinoxalin-2(1H)-Ones with Aryltriazenes under Catalyst-Free and Ambient Conditions

A photo-induced direct arylation of quinoxalin-2(1H)-ones with aryltriazenes under catalyst-free and ambient conditions was developed. The synthetic importance of this methodology was showcased by the simple operation, good functional group tolerance, and gram-scale synthesis.     

Photoredox-Controlled Mono- and Di-Multifluoroarylation of C(sp3)−H Bonds with Aryl Fluorides

A controllable mono- and di-multifluoroarylation of acyclic and cyclic N-aryl amines with aryl fluorides by photocatalyzed dual C(sp³)−H/C(sp²)−F functionalization has been developed, providing new access to a wide array of valuable α-fluoroarylated amines. In addition, the one-pot consecutive hetero-di-multifluoroarylation of N-aryl pyrrolidines and N,N-dimethylanilines was achieved with high to excellent diastereoselectivity. This new defluorinative C(sp³)−C(sp²) coupling is distinguished by a broad scope, good regioselectivity, and mild conditions as well as gram-scale and late-stage applicability, and thus constitutes a significant advance in the arylation of unactivated C(sp³)−H bonds with aryl fluorides.     

De-Linker-Enabled Exceptional Volumetric Acetylene Storage Capacity and Benchmark C2H2/C2H4 and C2H2/CO2 Separations in Metal–Organic Frameworks

An ideal adsorbent for separation requires optimizing both storage capacity and selectivity, but maximizing both or achieving a desired balance remain challenging. Herein, a de-linker strategy is proposed to address this issue for metal–organic frameworks (MOFs). Broadly speaking, the de-linker idea targets a class of materials that may be viewed as being intermediate between zeolites and MOFs. Its feasibility is shown here by a series of ultra-microporous MOFs (SNNU-98-M, M=Mn, Co, Ni, Zn). SNNU-98 exhibit high volumetric C₂H₂ uptake capacity under low and ambient pressures (175.3 cm³ cm⁻³ @ 0.1 bar, 222.9 cm³ cm⁻³ @ 1 bar, 298 K), as well as extraordinary selectivity (2405.7 for C₂H₂/C₂H₄, 22.7 for C₂H₂/CO₂). Remarkably, SNNU-98-Mn can efficiently separate C₂H₂ from C₂H₂/CO₂ and C₂H₂/C₂H₄ mixtures with a benchmark C₂H₂/C₂H₄ (1/99) breakthrough time of 2325 min g⁻¹, and produce 99.9999 % C₂H₄ with a productivity up to 64.6 mmol g⁻¹, surpassing values of reported MOF adsorbents.     

Preparation of Pt／C Catalyst with a New and Simple Organic Sol Method

It is reported for the first time that the Pt/C catalyst can be prepared with a new and simple organic sol method using SnCl2 as the reductant. It was found that the average size of the Pt particles in the Pt/C catalysts could be controlled with controlling the preparation conditions. The effect of the average sizes of the Pt particles in the Pt/C catalysts obtained with this method on the electrocatalytical activity of the oxidation of methanol was investigated.     

Enantio- and Diastereoswitchable C−H Arylation of Methylene Groups in Cycloalkanes

A complementary set of chiral N,N-ligands enables the Pd-catalyzed β-C−H arylation of unbiased internal methylene groups in good yield and with high levels of enantio- and diastereoinduction. Both the dia- and enantioselectivity can be reversed, thus allowing the selective arylation of any of the four β-C−H bonds in cycloalkanecarboxamides of various ring sizes. The method is applicable to a broad range of aryl iodides with electron-withdrawing and -donating substituents in the o-, m-, or p-position.     

Heck Arylation of Acrylonitrfle with Aryl Iodides Catalyzed by a Silica-bound Arsine Palladium（0） Complex

Acrylonitrile reacts with aryl iodides in the presence of tri-n-butylamine and a catalytic amount of a silica-bound arsine palladium(O) complex to afford stereoselectively (E)-cinnamonitriles in high yields.     

Heck Arylation of Acrylonitrile with Aryl Iodides Catalyzed by a Silica-bound Arsine Palladium(0) Complex

The palladium-catalyzed arylation of alkenes is an important discovery in organo-palladium chemistry made by Heck et al. and has found wide application in organicsynthesis1,2. In this reaction, homogeneous palladium complexes such as Pd(OAc)2 areusually used as the catalysts and the amount of catalyst used is about 2 mol% of reactant.Although homogeneous palladium catalysts have proven to be efficient, their activity andstereoselectivity are moderate and use of homogeneous palladium catalysts…