RESUMEN

A ruthenium-catalyzed para-selective alkylation of protected anilines to construct α-arylacetonitrile skeletons has been reported. We firstly disclosed the ethyl 2-bromo-2-cyanopropanoate was an effective alkylating reagent in ruthenmuim-catalyzed remote-selective C-H functionalization. A wide variety of α-arylacetonitrile skeletons can be directly obtained with moderate to good yields. Importantly, the products contain both nitrile and ester groups guaranteeing its direct transformation into other useful synthetic units, indicating the synthetic importance of this method.

RESUMEN

It has always been a challenge in free radical chemistry to control site selectivity during the reaction of free radicals with aromatic rings. Herein, we report the site-selective carboxylation of anisoles through the direct reaction of the bromoform radical with a benzene ring at the para position under the assistance of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline with nickel(II) as the catalyst. A wide variety of anisoles were compatible, leading to para-carboxylated products in moderate to good yields. A preliminary mechanistic study suggested that the Ni(II) complex coordinates with the methoxyl group of the aromatic ring, which may have increased the steric hindrance at the ortho and meta positions, while this weak interaction reduces the aromaticity of the aromatic ring, affording an activated phenyl ring, thereby leading to highly para-selective carboxylation.

RESUMEN

With pyrimidine as the directing group, we achieved the meta-selective difluoromethylation of phenol derivatives using ruthenium as a catalyst. This synthetic scheme provided an efficient method for the syntheses of fluorine-containing phenol derivatives. A wide variety of phenol derivatives were well-suited, affording the corresponding products in moderate-to-good yields.

RESUMEN

Highly efficient, palladium-catalyzed, para-selective difluoromethylation of arene esters has been developed using [1,1'-biphenyl]-2-dicyclohexylphosphine as the effective ligand. A wide variety of arene esters bearing various functional groups were all compatible with the reaction conditions, leading to para-difluoromethylated products in moderate to good yields. Moreover, benzoylamide and benzenesulfonamide were also well-tolerated, suggesting that this novel catalyst system has broad applications to a variety of substrates.

RESUMEN

A practical and highly para-selective C-H difluoromethylation of aromatic ketones has been developed by employing tetrakis(triphenylphosphine)palladium(0) as the catalyst and triphenylphosphine as the ligand. In addition to general aromatic ketones, this transformation was compatible with bioactive compounds and well-known drugs, such as oxybenzone, ketoprofen, zaltoprofen, and propafenone. Moreover, a mechanistic study revealed that a palladium intermediate coordinated by a carbonyl group promotes highly para-selective difluoromethylation.

Asunto(s)

Hidrocarburos Aromáticos/química , Cetonas/química , Paladio/química , Catálisis , Halogenación , Ligandos , Metilación

RESUMEN

A highly efficient rhodium(III)-catalyzed direct oxidative annulation of acrylic acid with alkynes to form α-pyrones was developed. Various substituted acrylic acids were compatible in this transformation, affording the corresponding products in moderate to excellent yields under mild conditions.

RESUMEN

A highly efficient silver-catalyzed dibenzylation of acetanilides by employing the benzhydrol derivatives as the coupling partners to yield triphenylmethane derivatives has been developed. Various functional groups were tolerated, leading to the corresponding products in moderate to good yields. Preliminary experimental results indicated that the silver ions activate the arene rings and the strong acid TfOH provides the carbocations.

RESUMEN

The selective arylation of unactivated ß or challenging γ primary and secondary ß-C(sp3)-H bonds has been developed with a Cp*Rh(III) catalyst assisted by a trimethylpyrazole group. A rarely reported six-membered rhodacycle has been identified in rhodium-catalyzed C(sp3)-H activation reactions. Preliminary mechanistic studies have revealed that a concerted metalation-deprotonation pathway might be involved in the C-H activation step.