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.

本研究报道了一种基于碳氢键（C–H）活化策略制备二苯并环庚酮的简便高效合成方法。以邻位芳酰化的3,5-二芳基异噁唑为起始底物，经钯催化的分子内C–H/C–Br键交叉偶联反应，可得到一系列连有异噁唑基团的二苯并环庚酮类产物，氢核磁共振（¹H NMR）产率范围为24%至>99%。通过X射线晶体衍射确证了所得二苯并环庚酮的结构。所开发的合成方法展现出优异的官能团耐受性。此外，本研究还提出了合理的反应机理以阐释该反应历程。对于所制备的二苯并环庚酮类化合物，以六羰基钼[Mo(CO)₆]为催化剂，可方便地将其异噁唑环转化为β-氨基烯酮基团。最终，通过X射线晶体衍射验证了预期的开环产物——连有β-氨基-α-酮基团的二苯并环庚烯酮的结构。