Ap ractical and highly para-selective CÀHd ifluoromethylation 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,t his transformation was compatible with bioactive compounds and well-known drugs,s uch as oxybenzone,ketoprofen, zaltoprofen, and propafenone.Moreover,amechanistic study revealed that apalladium intermediate coordinated by ac arbonyl group promotes highly paraselective difluoromethylation.
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.
The selective arylation of unactivated β or challenging γ primary and secondary β-C(sp)-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(sp)-H activation reactions. Preliminary mechanistic studies have revealed that a concerted metalation-deprotonation pathway might be involved in the C-H activation step.
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.
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.
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