Air-promoted direct radical arylation of anilines with arylhydrazines

Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids forming o-amino biaryls

We report a Pd-catalyzed ortho-C-H arylation of free anilines with arylboric acids. Under the reaction conditions, a wide range of arylboric acids can couple with free anilines to produce the corresponding o-amino biaryls in moderate to good yields with good functional group tolerance. This reaction can be conducted on the gram scale. The products can be easily further functionalized via transformation of the free amino group. These results indicate the potential synthetic value of this new reaction in organic synthesis.

Palladium-Catalyzed Ortho C-H Arylation of Unprotected Anilines: Chemo- and Regioselectivity Enabled by the Cooperating Ligand [2,2'-Bipyridin]-6(1H)-one

Metal-catalyzed C-H functionalizations on the aryl ring of anilines usually need cumbersome N-protection-deprotection strategies to ensure chemoselectivity. We describe here the Pd-catalyzed direct C-H arylation of unprotected anilines with no competition of the N-arylation product. The ligand [2,2'-bipyridin]-6(1H)-one drives the chemoselectivity by kinetic differentiation in the product-forming step, while playing a cooperating role in the C-H cleavage step. The latter is favored in an anionic intermediate where the NH moiety is deprotonated, driving the regioselectivity of the reaction toward ortho substitution.

Generation of aryl radicals by redox processes. Recent progress in the arylation methodology

Arylation methods based on the generation and use of aryl radicals have been a rapidly growing field of research in recent years and currently represent a powerful strategy for carbon – carbon and carbon – heteroatom bond formation. The progress in this field is related to advances in the methods for generation of aryl radicals. The currently used aryl radical precursors include aryl halides, aryldiazonium and diaryliodonium salts, arylcarboxylic acids and their derivatives, arylboronic acids, arylhydrazines, organosulfur(II, VI) compounds and some other compounds. Aryl radicals are generated under mild conditions by single electron reduction or oxidation of precursors induced by conventional reagents, visible light or electric current. A crucial role in the development of the radical arylation methodology belongs to photoredox processes either catalyzed by transition metal complexes or organic dyes or proceeding without catalysts. Unlike the conventional transition metal-catalyzed arylation methods, radical arylation reactions proceed very often at room temperature and have high functional group tolerance. Without claiming to be exhaustive, this review covers the most important advances of the current decade in the generation and synthetic applications of (het)aryl radicals. Examples of reactions are given and mechanistic insights are highlighted.

The bibliography includes 341 references.

Arylhydrazines: novel and versatile electrophilic partners in cross-coupling reactions

Arylhydrazines are extremely valuable compounds in organic chemistry that are widely used for the synthesis of a variety of biologically active molecules such as indoles, indazoles, pyrazoles, aryltriazoles, β-lactams and quinazolines. These compounds have also been widely utilized as arylation agents in oxidative cross-coupling reactions. In this review, we will highlight the most important explorations and developments in the carbon-carbon and carbon-heteroatom (nitrogen, phosphorus, sulfur, and selenium) cross-coupling of arylhydrazines. The literature has been surveyed from 2001 to June 2018.

Denitrogenative palladium-catalyzed coupling of aryl halides with arylhydrazines under mild conditions

A novel, simple, and efficient protocol via Pd(ii)-catalyzed denitrogenative coupling of arylhydrazines with aryl halides under ambient and mild conditions.

AgNO3-catalyzed direct C–H arylation of quinolines by oxidative decarboxylation of aromatic carboxylic acids

AgNO₃-catalyzed direct C–H arylation of quinolines by oxidative decarboxylation of aromatic carboxylic acids to afford aryl quinoline derivatives in moderate yields was described.

Transition-metal-free oxidative reaction of hydrazines and potassium metabisulfite for preparation of sulfonohydrazides

A coupling reaction for the synthesis of sulfonohydrazides from two types of hydrazines and K₂S₂O₅ under air was developed.

Acid-promoted denitrogenative Pd-catalyzed addition of arylhydrazines with nitriles at room temperature

Pd(TFA)₂-catalyzed denitrogenative addition proceeded with selective C–N bond cleavage of arylhydrazines with nitriles under air at room temperature.

Regioselective C-3 arylation of coumarins with arylhydrazines via radical oxidation by potassium permanganate

An efficient protocol for oxidative C-3 arylation of coumarins with arylhydrazine has been developed using potassium permanganate as an oxidant. The arylated coumarins with different electronic properties were obtained in moderate to good yields. The developed protocol for direct C-3 arylation of coumarins could be extended to quinolinones.

Palladium-catalyzed aerobic oxidative cross-coupling of arylhydrazines with terminal alkynes

The Pd-catalyzed aerobic oxidative coupling of arylhydrazines with terminal acetylenes was achieved under copper- and base-free conditions.