title: Catalytic B-H Bond Insertion Reactions Using Alkynes as Carbene Precursors.
abstract: Herein, we report transition-metal-catalyzed B-H bond insertion reactions between borane adducts and alkynes to afford organoboron compounds in excellent yields under mild reaction conditions. This successful use of alkynes as carbene precursors in these reactions constitutes a new route to organoboron compounds. The starting materials are safe and readily available, and the reaction exhibits 100% atom-economy. Moreover, an asymmetric version catalyzed by chiral dirhodium complexes produced chiral boranes with excellent enantioselectivity (up to 96% ee). This is the first report of highly enantioselective heteroatom-hydrogen bond insertion reactions of metal carbenes generated in situ from alkynes. The chiral products of the reaction could be easily transformed to widely used borates and diaryl methanol compounds without loss of optical purity, which demonstrates its potential utility in organic synthesis. A kinetics study indicated that the Cu-catalyzed B-H bond insertion reaction is first order with respect to the catalyst and the alkyne and zero order with respect to the borane adduct, and no kinetic isotopic effect was observed in the reaction of the adduct. These results, along with density functional theory calculations, suggest that the formation of the Cu carbene is the rate-limiting step and that the B-H bond insertion is a fast, concerted process.
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.
authors.forename: Ji-Min
authors.initials: JM
authors.lastname: Yang
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.
authors.forename: Zi-Qi
authors.initials: ZQ
authors.lastname: Li
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.
authors.forename: Mao-Lin
authors.initials: ML
authors.lastname: Li
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.
authors.forename: Qiao
authors.initials: Q
authors.lastname: He
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.
authors.forename: Shou-Fei
authors.identifier: 0000-0002-6055-3139
authors.initials: SF
authors.lastname: Zhu
authors.affiliation: State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University , Tianjin 300071, China.|Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University , Tianjin 300071, China.
authors.forename: Qi-Lin
authors.identifier: 0000-0002-4700-3765
authors.initials: QL
authors.lastname: Zhou