1279692-99-7Relevant academic research and scientific papers
Synthetic and mechanistic studies of metal-free transfer hydrogenations applying polarized olefins as hydrogen acceptors and amine borane adducts as hydrogen donors
Yang, Xianghua,Fox, Thomas,Berke, Heinz
, p. 852 - 860 (2012)
Metal-free transfer hydrogenation of polarized olefins (RR′ CCEE′: R, R′ = H or organyl, E, E′ = CN or CO2Me) using amine borane adducts RR′NH-BH3 (R = R′ = H, AB; R = Me, R′ = H, MAB; R = tBu, R′ = H, tBAB; R = R′ = Me, DMAB) as hydrogen donors, were studied by means of in situ NMR spectroscopy. Deuterium kinetic isotope effects and the traced hydroboration intermediate revealed that the double H transfer process occurred regio-specifically in two steps with hydride before proton transfer characteristics. Studies on substituent effects and Hammett correlation indicated that the rate determining step of the HN transfer is in agreement with a concerted transition state. The very reactive intermediate [NH2BH2] generated from AB was trapped by addition of cyclohexene into the reaction mixture forming Cy2BNH2. The final product borazine (BHNH)3 is assumed to be formed by dehydrocoupling of [NH2BH2] or its solvent stabilized derivative [NH2BH2]-(solvent), rather than by dehydrogenation of cyclotriborazane (BH2NH 2)3 which is the trimerization product of [NH 2BH2].
Facile metal free regioselective transfer hydrogenation of polarized olefins with ammonia borane
Yang, Xianghua,Fox, Thomas,Berke, Heinz
, p. 2053 - 2055 (2011/03/22)
Transfer hydrogenation of polarized olefins bearing strongly electron-withdrawing groups on one side of the double bond was achieved with ammonia borane under mild conditions without using a catalyst. Mechanistic studies proved the character of the direct H transfers proceeding stepwise with a unique hydroboration intermediate and hydride before proton transfer.
