Palladium‐Catalyzed Oxidative C?H Bond Acylation of Acetanilides with Benzylic Alcohols

An efficient and clean method to construct C C bonds has been developed via the acylation reaction of acetanilides with benzylic alcohols using tert‐butyl hydroperoxide (TBHP) as oxidant catalyzed by palladium acetate in the presence of triflic acid (TfOH). The acylation reactions exhibit excellent reactivities, and up to 95% yield of the corresponding aryl ketone could be obtained under the optimal conditions.     

Mild Palladium‐Catalyzed Oxidative Direct ortho‐C?H Acylation of Anilides under Aqueous Conditions

Palladium‐catalyzed cross‐dehydrogenative coupling between anilides and aromatic aldehydes was achieved under aqueous conditions. A wide variety of the desired benzophenone derivatives was isolated in good to excellent yield. The reaction rate acceleration effect of acid and detergent has been demonstrated. Mechanistic insight has been obtained from quantum chemical calculations.     

Palladium‐Catalyzed Oxidative Intramolecular C?C Bond Formation via Double sp2 C?H Activation between the 2‐Position of Imidazoles and a Benzene Ring

Oxidative intramolecular C C bond formation via double sp² C H activation between the 2‐position of imidazoles and a benzene ring catalyzed by palladium(II) has been developed, which provides an atom‐economical, concise and efficient methodology to synthesize imidazole‐ or benzimidazole‐fused isoquinoline polyheteroaromatic compounds.     

C?C Bond Formation via C?H Activation and C?N Bond Formation via Oxidative Amination Catalyzed by Palladium‐ Polyoxometalate Nanomaterials Using Dioxygen as the Terminal Oxidant

An efficient heterogeneous palladium‐polyoxometalate catalyst with the formula Pd‐H₆PV₃Mo₉O₄₀/C has been successfully developed for carbon‐carbon (C C) bond formation via carbon‐hydrogen (C H) activation and carbon‐nitrogen (C N) bond formation via oxidative amination using oxygen as the terminal oxidant. The coupling processes are simple, and use relatively mild conditions to form the desired products. In addition, less waste is generated as no additional reagents such as organic/inorganic oxidants are required, and water is the only by‐product generated.     

Iron‐Catalyzed C?C Bond Cleavage and C?N Bond Formation

A novel approach for C N bond formation was developed by iron‐catalyzed C C bond cleavage. Anilines and sulfonamides reacted smoothly with 2‐substituted 1,3‐diphenylpropane‐1,3‐diones to afford N‐alkylation products, in which the 1,3‐dicarbonyl group acts as a leaving group in the presence of an iron catalyst. The reversible C C bond cleavage plays a driving force to give the thermodynamically stable products. The method is complementary to the previous methods for C N bond formation.     

Efficient Palladium‐Catalyzed Oxidative Indolation of Allylic Compounds with DDQ via sp3 C?H Bond Activation and Carbon‐Carbon Bond Formation Under Mild Conditions

An efficient oxidative cross‐coupling reaction between 1,3‐diarylpropenes and indoles in the presence of palladium chloride was achieved with 2,3‐dichloro‐5,6‐dicyanoquinone (DDQ) as oxidant. The reaction afforded 1,3‐diphenylallylindoles in moderate to high yields under mild conditions, thus providing a novel methodology to synthesize the respective products.     

Palladium‐Catalyzed Oxidative Annulation via C?H/N?H Functionalization: Access to Substituted Pyrroles

Pyrroles, ubiquitous bioactive heterocycles in nature, are readily prepared via a palladium‐catalyzed oxidative annulation of cyclic trans‐enamines to various internal alkynes in the absence of a directing group.

     

Synthesis of [60]Fullerene‐Fused Tetralones via Palladium‐ Catalyzed Ketone‐Directed sp2 C?H Activation and sp3 C?H Functionalization

The palladium‐catalyzed ketone‐directed dual sp² C H activation and sp³ C H functionalization has been applied for fullerene functionalization for the first time. The sec‐alkyl aryl ketones have been exploited to react with [60]fullerene (C₆₀) to provide the novel and scarce C₆₀‐fused tetralones. The combined use of a highly active cationic palladium(II) catalyst and trifluoromethanesulfonic acid is crucial for the improvement of the reaction yield. A plausible reaction mechanism leading to the observed products has been proposed, and the electrochemistry of the fullerene products has also been investigated.

     

Regioselective Cleavage of Unstrained C?C Bond and C?H Bond: Palladium–Copper Catalyzed Deacetophenonylative Arylation of Coumarin Derivatives

A C_α C_β bond activation of the carbonyl group in unstrained ketones catalyzed cooperatively by palladium and copper(II) with the departure of the acetophenone has been developed, and the subsequent coupling with a variety of aromatics via the formal C H activation similar to the Friedel–Crafts reaction affords the skeleton‐reconstructed coumarin derivatives with high regioselectivity.     

Palladium‐Catalyzed/Lewis Acid‐Promoted Alkene Dimerization and Cross‐Coupling with Alcohols via C?H Bond Activation

The cross‐couplings of alcohols to alkenes with the palladium/Lewis acid system are reported. This reaction occurs in a successive alkene dimerization, direct C H activation of alcohol and sp³ sp³ bond forming sequence via an interesting domino process.     

Carbon Nitride‐Catalyzed Photoredox C?C Bond Formation with N‐Aryltetrahydroisoquinolines

In this communication we describe the oxidative C C bond formation of tertiary amines with various nucleophiles under very mild and environmental friendly conditions by using mesoporous graphitic carbon nitride (mpg‐C₃N₄) semiconductor as a heterogeneous, metal‐free photosensitizer in combination with visible light and oxygen as the terminal oxidation agent. This system can be further combined with proline‐organocatalysis to achieve oxidative tandem photocatalysis, demonstrating a rich cascade of chemical possibilities of the current photosynthesis system.     

A Metal‐Free Oxidative Esterification of the Benzyl C?H Bond

An efficient metal‐free oxidative esterification of benzyl C H bonds was developed. Using tetrabutylammonium iodide as catalyst and tert‐butyl hydroperoxide as co‐oxidant, benzylic substrates could react smoothly with various carboxylic acids to give the esters with good to excellent yields. The method was also suitable for the O‐protection of N‐Boc amino acids. The reaction mechanism was primarily investigated and a radical process was proposed.     

Palladium‐Catalyzed Selective C?H Benzylation towards Functionalized Azoles with a Quaternary Carbon Center

The direct C H benzylation of azoles with benzyl chlorides proceeds efficiently, via sequential cleavage of one sp² C H bond and two sp³ C H bonds in the presence of a palladium catalyst, to generate a wide range of tribenzylated azoles with a quaternary carbon center efficiently. The same catalyst could also promote the mono‐ and di‐benzylation reactions through fine turning of the base and reaction conditions.     

Phosphaannulation of Aryl‐ and Benzylphosphonic Acids with Unactivated Alkenes via Palladium‐Catalyzed C?H Activation/Oxidative Cyclization Reaction

An efficient phosphaannulation via palladium(II)‐catalyzed C H activation/oxidative cyclization by the 6‐endo mode is reported for the synthesis of 3‐substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α‐disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)‐alkylidenyl groups via anti‐phosphoryloxypalladation by the 6‐exo mode.

     

Copper‐Catalyzed Direct Arylselenation of Anilines by C?H Bond Cleavage

We describe here an efficient and regioselective synthesis of arylselanyl anilines by copper‐catalyzed direct arylselenation of arylamines. Using a catalytic amount of copper iodide in dimethyl sulfoxide at 110 °C under an air atmosphere, a range of arylselanyl anilines was obtained directly from substituted diaryl diselenides in moderate to good yields via C H bond cleavage of aryl amines.

     

Zinc‐Catalyzed Organic Synthesis: C?C,C?N,C?O Bond Formation Reactions

Zinc is the 24^th most abundant element in the Earth’s crust. Since the discovery of pure zinc metal in the 18^th century, the main application of zinc metal is as materials. Because zinc salts are abundant, cheap, non‐toxic, and exhibit environmentally benign properties, organic chemists have been interested in using zinc salts as catalysts in organic synthesis during the last three decades. Within this review, we have summarized the progress on applications of zinc salts in organic reactions. Our the target is to emphasize the special properties of zinc catalysts, and further promote the interest of organic chemists.     

Iron‐Catalyzed C?H Fuctionalization of Indoles

An easily available iron catalyst was developed to accomplish the C H functionalization of indoles with α‐aryl‐α‐diazoesters in high yields under mild conditions. The asymmetric C H functionalization of indoles was also realized by using iron complexes of chiral spiro bisoxazolines with up to 78% ee.     

Palladium(II)‐Catalyzed Direct ortho‐C?H Acylation of Anilides by Oxidative Cross‐Coupling with Aldehydes using tert‐Butyl Hydroperoxide as Oxidant

An efficient palladium‐catalyzed C H acylation with aldehydes using tert‐butyl hydroperoxide (TBHP) transforms various anilides into synthetically useful 2‐aminobenzophenone derivatives under mild conditions (40 °C, 3 h). The acylation reaction exhibits excellent regioselectivity and functional group tolerance, and simple aromatic aldehydes, functionalized aliphatic aldehydes and heteroaromatic aldehydes are effective coupling partners. The acylation reaction is probably initiated by a rate‐limiting electrophilic C H cyclopalladation (k_H/k_D=3.6; ρ⁺=−0.74) to form an arylpalladium complex, followed by acyl radical functionalization.     

Copper‐Catalyzed Highly Regioselective Oxidative C?H Bond Amidation of 2‐Arylpyridine Derivatives and 1‐Methylindoles

Copper(I) bromide‐catalyzed amidation of 2‐arylpyridine derivatives and 1‐methylindoles with a variety of amides was achieved by employing tert‐butyl peroxide (TBP) as oxidant. Aryl halides could be tolerated under the reaction conditions. Neither a special ligand nor a base was required for this amidation process.     

Palladium‐Catalyzed C?H Bond Acetoxylation: An Approach to ortho‐Substituted Hydroxy[2.2]paracyclophane Derivatives

The palladium‐catalyzed direct C H bond acetoxylation of [2.2]paracyclophanes has been investigated. Various mono‐ and disubstituted [2.2]paracyclophanes were subjected to typical Sanford acetoxylation conditions. Oxime ethers, an oxime acetate, a pyridine, and a pyrazole with [2.2]paracyclophane cores underwent direct ortho‐acetoxylation in good to excellent yields using 1–5 mol% of palladium(II) acetate in combination with iodobenzene diacetate as oxidant. The reactions could be performed on a multigram scale, and the ortho‐acetoxylated [2.2]paracyclophanes were suitable for further functionalizations affording a hydroxy[2.2]paracyclophane derivative and a planar chiral benzoxazole.