Research On Rh(?)-Catalyzed Aromatic Amide Guided Alkenylation/Annulation Of Closo-dodecaborate Dianions

The closo-dodecaborate dianion is a fundamental icosahedral boron cage with 12 identical B-H vertices.It features delocalized sphere-like electron distribution and extraordinary thermal and chemical stability as well as low toxicity.Thus,it is regarded as a 3D analogue of benzene.These characteristics endow the cluster with great prospects as weakly coordinating anions,in medicinal chemistry,ligand design,host-guest chemistry,catalysis,and materials science.However,due to its excellent stability and high symmetry,the challenge of selective modification of the cage positions has remained for decades.Herein,a rhodium(?)-catalyzed B-H functionalization-cyclization cascade of closo-dodecaborate amides is reported.The transformations occur chemoselectively at B-H positions in the presence of C-H bonds prone to competitive cyclometalation.Previously inaccessible cage derivatives with B-C(sp2)and B-C(sp3)bonds as well as a fused diboraoxazole ring are obtained in a one-pot process.The reactions proceed under mild conditions and exhibit complete cage regioselectivity with broad functional group tolerance.A plausible reaction mechanism is also proposed based on the separation of a probable key intermediate.