Deoxygenative Haloboration and Enantioselective Chloroboration of Carbonyls.

Deoxygenative difunctionalization of carbonyls affords a straightforward and effective route to construct geminal dual functionalized motifs. However, the research in this field is very challenging due to the strong bond dissociation energies of the C-O double bond or the subsequently formed C-O bond. Herein, we report a highly efficient deoxygenative haloboration of aldehydes to generate secondary α-haloboronates. Meanwhile, the difficult-to-obtain tertiary α-haloboronates can be also readily prepared via the same strategy with ketones. Furthermore, enantioselective chloroboration of carbonyls was successfully achieved to give chiral secondary or tertiary α-chloroboronates, the important intermediates to access enantioenrich multisubstituted stereocenters. These versatile products can be surprisingly attained through this simple and mild process with remarkable substrate scope expansion and functional group tolerance. Additionally, these reactions can proceed well on large scales, giving more practical values in the application.