| Selective C-C bond activation is one of the most challenging tasks in organic chemistry owing to its high bond energy.In recent years,transition-metal-catalyzed ring-opening/coupling reaction of benzocyclobutenols has attracted extensive attention of scientists due to its special reactivity.Benzocyclobutanol can break the C-C bond to obtain the corresponding arylmetal species under transition metal catalysis,and then construct various types of compounds by coupling reaction.In this paper,the oxindoles was constructed by Palladium-catalyzed Heck reaction,and a series of 3,3′-disubstituted oxindoles were synthesized by coupling reaction with C(sp~2)-C(sp~3)/C(sp~3)-C(sp~3)between the ring-opening products of benzocyclobutenols.In the first part,we realized a Pd-catalyzed selective ring-opening/coupling reaction with2-iodophenyl acrylamide and benzocyclobutanol.Under the mild reaction conditions,a palladium-catalyzed Heck coupling/C-C bond activation reaction of o-iodophenyl acrylamide with benzocyclobutanol was carried out,and a series of oxindoles were obtained in excellent yields(up to 99%)through intermolecular C(sp~2)-C(sp~3)coupling.The target product can also be obtained in 96%yield when the reaction was scaled up to gram scale.In addition,we also obtained the preliminary enantioselective reaction results(49%yield,41%ee).In the second part,we studied the Pd-catalyzed selective ring-opening/coupling reaction with N-(2-bromobenzoyl)indole and benzocyclobutanol.In this part,through the regulation of the catalytic system,we can change the ring-opening site of benzocyclobutanol,and the corresponding target products was obtained selectively.when the chiral sulfonyl imide ligands are added in the system,the reaction can obtained C(sp~2)-C(sp~3)coupling products with 87%ee,but in only 30%yield.when the binaphthol skeleton ligand containing TMS was added into the system,the C(sp~3)-C(sp~3)coupling product could be obtained with 82%yield and 90%ee. |
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