Rh(II)-Catalyzed Enantioselective B–H Insertion of Cyclic Alkyl-Donor Carbene Generated from Diynes

An enantioselective B-H bond insertion has been developed by employing a cyclic alkyl-donor carbene generated from diynes. Using trimethylamine borane, the reaction provides boron-substituted furan-fused dihydropiperidines bearing a carbon stereocenter, whereas 2-arylpyridine borane delivers products containing vicinal carbon/boron stereocenters with high enantioselectivity through a desymmetric B-H insertion process. This method effectively suppresses the competing 1,2-H migrations typically favored by alkyl carbenes. Furthermore, diverse transformations of the resulting B-H insertion products have been demonstrated.