Recent Advances in the Pd-Catalyzed Coupling of Arylhydrazines and Ammonium Salts via C-N Bond Cleavage

Both arylhydrazines and quaternary ammonium salts are readily accessible or commercially available chemicals that show versatile reactivity in Pd-catalyzed coupling reactions via C-N bond cleavage. A tremendous array of coupling reactions involving reaction partners such as organoborons, aryl silanes, alkenes, alkynes, arylation or alkylation reagents in C-H functionalization and carbonylation reactions are summarized, in which arylhydrazines or quaternary ammonium salts function as aryl or alkyl donors. This account mainly focuses on recent advances in Pd-catalyzed coupling reactions with arylhydrazines or quaternary ammonium salts via C-N bond cleavage, including mechanistic elucidations.

"Benchtop" Biaryl Coupling Using Pd/Cu Cocatalysis: Application to the Synthesis of Conjugated Polymers

Typically, Suzuki couplings used in polymerizations are performed at raised temperatures in inert atmospheres. As a result, the synthesis of aromatic materials that utilize this chemistry often demands expensive and specialized equipment on an industrial scale. Herein, we describe a bimetallic methodology that exploits the distinct reactivities of palladium and copper to perform high yielding aryl-aryl dimerizations and polymerizations that can be performed on a benchtop under ambient conditions. These couplings are facile and can be performed by simple mixing in the open vessel. To demonstrate the utility of this method in the context of polymer synthesis: polyfluorene, polycarbazole, polysilafluorene, and poly(6,12-dihydro-dithienoindacenodithiophene) were created at ambient temperature and open to air.

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.

Transition-Metal Catalyst Free Oxidative Radical Arylation of N-Methylpyrrole

This study represents an expansion of the application of catalysis in air through conventional coupling and free radical processes. A reactive free aryl radical intermediate was generated via the oxidation of an activated Ar-NH-NH₂ bond by air as a simple and readily available oxidant. For this purpose, the usability of phenylhydrazine and phenylhydrazine hydrochloride salt reagents for the direct arylation of pyrrole with aryl radicals was investigated. The facile coupling of N-methylpyrrole with aryl radicals was easily applied for the convenient direct synthesis of C-2 arylated pyrroles without a transition-metal catalyst.

Regioselective α-arylation of coumarins and 2-pyridones with phenylhydrazines under transition-metal-free conditions

A transition-metal-free regioselective α-arylation of coumarins and 2-pyridones has been accomplished by the reaction of phenylhydrazines with coumarins or 2-pyridones.

p-TsOH-promoted synthesis of (E)-6-phenyl-7-styryl-5,6-dihydrodibenzo[b,h][1,6]naphthyridines via cascade intramolecular aza-Michael addition/Friedlander condensation of 2′-aminochalcones in a SDS/H2O system

p-TsOH-promoted one-pot cascade synthesis of novel (E)-6-phenyl-7-styryl-5,6-dihydrodibenzo[b,h][1,6]naphthyridines via homodimerization of 2′-aminochalcones has been developed in a SDS/H₂O system.