A synthetic
methodology for the late-stage ortho-C–H bond
aroylation of anilines with aryl aldehydes led to a variety of ortho-aroylated anilines by the use of palladium(II) acetate, tert-butyl hydroperoxide, and 1,4-dioxane as the catalyst,
oxidant, and solvent, respectively, is presented. An N-phenylpyridin-2-amine palladacycle was isolated and characterized
by X-ray crystallography. Controlled experiments, radical trapping
experiments, and the experiments of the kinetic isotope effect were
undertaken to support the proposed reaction mechanism. Syntheses of
2-aminobenzophenone and 9(10H)-acridanone based on
the developed methodology were successfully demonstrated.
We present a stoichiometric
methodology for the synthesis of 4-arylated/alkylated
9(10H)-acridinones via a palladium-mediated ortho-C–H bond activation and C–C bond cross-coupling
strategy. In the reaction, a N-(pyridin-2-yl)-9(10H)-acridinone palladacycle was employed as the starting
substrate, which could be readily prepared by the stoichiometric reaction
of N-(pyridin-2-yl)-9(10H)-acridinone
and palladium(II) acetate in 89% isolated yield. Meanwhile, potassium
aryl/alkyltrifluoroborates and p-benzoquinone were
introduced to serve as the coupling partner and reaction promoter,
respectively, in the presented palladium-mediated ortho-C–H bond arylation/alkylation of 9(10H)-acridinone.
The reaction eventually furnished a variety of 4-arylated/alkylated
9(10H)-acridinones in 31–95% yields. The structures
of N-(pyridin-2-yl)-9(10H)-acridinone
palladacycle substrate and 4-phenylated/cyclopropylated 9(10H)-acridinone products were elucidated by X-ray crystallography.
Kinetic isotope effect studies, as well as controlled experiments,
were carried out to gain insight into the reaction mechanism. Finally,
the removal of the directing group (i.e., pyridin-2-yl) was demonstrated
on one of the ortho-arylated products, 4-phenyl-N-(pyridin-2-yl)-9(10H)-acridinone.
A facile and efficient synthetic methodology for preparing dibenzosuberones via a C−H bond activation strategy is presented. The ortho-aroylated 3,5-diarylisoxazole was employed as the starting substrate to undergo palladium-catalyzed intramolecular C−H/C−Br bond crosscoupling to produce a variety of dibenzosuberones bearing an isoxazole group in 24 to >99% 1 H NMR yields. The dibenzosuberone structure was further confirmed by X-ray crystallography. The developed methodology exhibits very good functional group tolerance. In addition, a rational mechanism was presented for describing the reaction process. For the prepared dibenzosuberone, the use of Mo(CO) 6 as the catalyst can easily transform the isoxazole ring into the β-aminoenone group. Finally, the structure of the anticipated ring-opening product, dibenzosuberenone, bearing a β-amino-α-ketone group was secured by X-ray crystallography.
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