Palladium‐Catalyzed Oxidative sp2 C?H Bond Acylation with Aldehydes

An efficient method was developed for the direct acylation of arene sp² C H bonds with aldehydes using palladium acetate as catalyst and peroxide as oxidant. The solvent‐free oxidative acylation reaction assisted by a pyridine directing group provides an easy access to aromatic, aliphatic, and optical active ketones.     

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.     

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.     

Transition Metal‐Catalyzed C?H Activation of Indoles

The last decades have seen a tremendous expanse in the application of C H activation of many different substrate classes, including the invaluable indole scaffold. Following the exciting emergence of C H activation as a multi‐faceted platform for functionalization, a versatile tool box has been developed for the preparation of structurally diverse indoles. This review article discusses recent advances and strategies for transition metal‐catalyzed C H activation of indoles.

     

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.     

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.

     

Ruthenium‐Catalyzed Remote Electronic Activation of Aromatic C?F Bonds

The tandem isomerization and nucleophilic aromatic substitution of allylic fluoro‐substituted benzylic alcohols is described for the first time. In the presence of the ruthenium complex Ru(PPh₃)₃(CO)(H)₂, 1‐(4‐fluorophenyl)prop‐2‐en‐1‐ol is converted into the corresponding para‐amino ketone or para‐phenolic substituted ketone.     

The Copper‐Catalyzed C‐3‐Formylation of Indole C?H Bonds using Tertiary Amines and Molecular Oxygen

A copper‐catalyzed formylation reaction has been developed by employing oxygen (O₂) as the clean oxidant. The C H bonds of indoles were C‐3‐formylated by tetramethylethylenediamine (TMEDA) and water (H₂O; in situ formed and external added water) as the carbonyl source in moderate to good yields with good functional group tolerance. Thus, it represents a facile procedure leading to 3‐formylindoles.     

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.     

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.     

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.     

Rhodium‐Catalyzed C?H Olefination of Aryl Weinreb Amides

A rhodium(III)‐catalyzed oxidative C H olefination directed by Weinreb amides, a class of well developed versatile building blocks in organic synthesis, has been developed with air as the terminal oxidant. The reactions proceed with excellent reactivity, good functional group tolerance and high yields.     

Lewis Acid‐Catalyzed Generation of C?C and C?N Bonds on π‐Deficient Heterocyclic Substrates

Focused microwave irradiation of a series of halogenated nitrogen heterocycles and different kinds of nucleophiles in the presence of a catalytic amount of indium trichloride leads to the efficient and completely regioselective generation of aromatic C C and C N bonds. The method is simple, rapid, general and inexpensive, and can be performed without the use of dried solvents. Most of the synthetized compounds are new and in many cases the work‐up required only filtration. Furthermore, this is the first example of the use of a Lewis acid as a catalyst for heteroarylation, vinylation and amination reactions on π‐deficient heterocyclic substrates.

     

Copper‐Catalyzed Intermolecular Amination of Acidic Aryl C?H Bonds with Primary Aromatic Amines

A copper‐catalyzed intermolecular aerobic oxidative C H bond amination of various polyfluorobenzenes with an array of primary aromatic amines was achieved for the first time. The reactivity of the polyfluorobenzenes was observed to depend on the acidity of C H bonds. Under similar reaction conditions, the C H bond amination of azoles also occurred.     

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.

     

Copper‐Catalyzed Cross‐Dehydrogenative Coupling (CDC) of Alkynes and Benzylic C?H Bonds

The activation of benzylic C H bonds and subsequent coupling with terminal alkynes in the presence of 2,3‐dichloro‐5,6‐dicyanoquinone (DDQ) and a catalytic amount of copper(I) triflate is presented. Good to moderate yields of disubstituted alkynes are obtained for this cross‐dehydrogenative coupling (CDC) reaction between a variety of aromatic alkynes and diphenylmethane derivatives.     

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.     

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 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.     

Bipyridine Periodic Mesoporous Organosilica: A Solid Ligand for the Iridium‐Catalyzed Borylation of C?H Bonds

With the goal to obtain a molecularly defined iridium(I) heterogeneous C H functionalization catalyst, a periodic mesoporous organosilica (PMO) containing bipyridylene moieties in a matrix of biphenylene units as ligand platform was designed and fully characterized. The material exhibits a high surface area with small mesopores in a vermicular arrangement, and the pore walls show a highly crystal‐like character. After surface passivation with chlorotrimethylsilane and functionalization with chloro(1,5‐cyclooctadiene)iridium(I) dimer [{IrCl(COD)}₂] a molecularly defined Ir(I) surface complex was obtained according to EXAFS and UV‐Vis spectroscopy. This functionalized material catalyzes the direct C H borylation of arenes to yield the corresponding boronic esters and can be reused without significant loss of activity.