Iridium‐Catalyzed Annulation of Aromatic Imines with 1,3‐Dienes via Direct Functionalization of an Aromatic C?H Bond

The [3+2] annulation of N‐sulfonyl aromatic imines with 1,3‐dienes proceeded via a direct C H functionalization to give 1‐aminoindane derivatives in high yields with high regio‐ and stereoselectivities. The iridium complex coordinated with a substrate 1,3‐diene displayed high catalytic activity. The reaction proceeds via the direct formation of the aryliridium(I) species from the aromatic aldimine and an iridium(I) acetate species via a concerted metalation‐deprotonation pathway.

     

Sequential Functionalization of the O?H and C(sp2)?O Bonds of Tropolones by Alkynes and N‐Sulfonyl Azides

Sequential copper‐catalyzed [3+2] cycloaddition, rhodium‐catalyzed O H insertion, intramolecular 1,8‐addition, and rearrangement starting from 1‐alkynes, N‐sulfonyl azides, and tropolones is demonstrated for the synthesis of the 2‐functionalized aminotropones in one pot. These results indicate that sequential functionalization of O H and C(sp²) O bonds smoothly occurs in the C(sp²) O H bonds of tropolone

     

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.

     

Synthesis of 3‐Aryl‐1‐trifluoromethyltetrahydroisoquinolines by Brønsted Acid‐Catalyzed C(sp3)?H Bond Functionalization

A concise route to 3‐aryl‐1‐trifluoromethyltetrahydroisoquinolines by a benzylic [1,5]‐hydride shift‐mediated C H bond functionalization was developed. The [1,5]‐hydride shift of the benzylic C(sp³) H bond to the trifluoromethylketimine derived from para‐anisidine occurred smoothly to produce cis‐1‐trifluoromethyl‐3‐aryltetrahydroisoquinolines in good to excellent chemical yields with good diastereoselectivities. In contrast, use of the N H ketimine furnished N‐unprotected tetrahydroisoquinolines in good yields in favor of the trans‐isomer.

     

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.     

Tandem Catalysis: Alcohol Oxidation and C?C Bond Formation via C?H Bond Activation

A tandem process involving oxidation of a benzylic alcohol functionality followed by hydroarylation is described. These two atom‐economic sequences are very convenient to access functionalized aromatic ketones, using simple ruthenium trichloride as catalyst precursor. Moreover they appear to be highly compatible, tolerant, and selective toward various functional groups, and the ease of the protocol should make it very convenient for synthetic purposes.     

Copper‐Mediated Sulfonylation of Aryl C(sp2)?H Bonds with Sodium and Lithium Sulfinates

A copper‐mediated direct sulfonylation of aryl C(sp²) H bonds with sodium and lithium sulfinates is reported. Various aryl sulfones were synthesized in moderate to excellent yields with good functional group tolerance.

     

Arene C?H Bond Functionalization Coupling with Cyclization of Allenes

Under the catalysis of a rhodium(III) complex, the cyclization of 2,3‐allenols was most probably initiated with the C H bond functionalization of N‐methoxybenzamides using the tetramethylcyclopentadiene anion (C₅Me₄⁻) as ligand, affording differently substituted 2,5‐dihydrofuran derivatives. Highly efficient axial‐to‐central chirality transfer has been observed.     

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.     

Visible Light‐Initiated C(sp3)?Br/C(sp3)?H Functionalization of α‐Carbonyl Alkyl Bromides through Hydride Radical Shift

A new visible light‐initiated 1,5‐hydride radical shift strategy has been developed to enable the one‐step functionalization of both a C(sp³) Br bond and a C(sp³) H bond adjacent to the same carbon atom. This visible light photoredox catalysis offers a mild and straightforward access to diverse five‐membered carbocyclic ring‐fused polycyclic hydrocarbons with high turnover numbers (TONs; up to 4.93×10³) and broad substrate scope.

     

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.

     

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.     

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.     

Nickel‐Catalyzed C?S Bond Formation: Synthesis of Aryl Sulfides from Arylsulfonyl Hydrazides and Boronic Acids

A practical nickel‐catalysed approach has been developed for the C S bond formation through the cross‐coupling of arylsulfonyl hydrazides and aryl boronic acids. The report employs arylsulfonyl hydrazide as an aryl thiol equivalent and offers a mild and eco‐safe synthesis of unsymmetrical thioethers in good to excellent yields in air. The scope and versatility of the method has been successfully demonstrated with 22 examples.

     

Palladium(II)‐Catalyzed Cycloamidination via C(sp2)?H Activation and Isocyanide Insertion

An efficient method for the synthesis of nitrogen heterocycles containing a cyclic amidine moiety has been developed. The process involves palladium‐catalyzed C(sp²) H activation and isocyanide insertion starting with readily accessible ortho‐heteroarene‐substituted aniline derivatives under mild conditions.     

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/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.     

Synthesis of tert‐Butyl Peroxyacetals from Benzyl,Allyl, or Propargyl Ethers via Iron‐Promoted C?H Bond Functionalization

When benzyl, allyl, and propargyl ethers were treated with tert‐butyl hydroperoxide and a catalytic amount of iron(III) acetylacetonate, tert‐butyl peroxyacetals were produced in good to excellent yields, via C H bond functionalization. This method is also applicable to ethylene acetals of unsaturated aldehydes to give peroxyorthoesters.     

Phenyliodine Diacetate‐Mediated Intramolecular C(sp2)?H Amidation for 1,2‐Disubstituted Benzimidazole Synthesis under Metal‐Free Conditions

A transition metal‐free, hypervalent iodine(III) reagent [phenyliodine diacetate (PIDA)]‐mediated C(sp²) H amidation in trifluoroethanol (TFE) has been developed. The intramolecular coupling methodology presented here provides a direct access to 1,2‐disubstituted multifunctional benzimidazoles in good to excellent yields. The reactions were performed in the open air and at ambient temperature, and were found to be eco‐friendly and atom‐economical.