Synthesis of Dibenzosuberones Bearing an Isoxazole Group via Palladium-Catalyzed Intramolecular C–H/C–Br Bond Cross-Coupling of Ortho-Aroylated 3,5-Diarylisoxazoles

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 cross-coupling
to produce a variety of dibenzosuberones bearing an isoxazole group
in 24 to >99% 1H 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.