4354-72-7Relevant articles and documents
Overcoming Selectivity Issues in Reversible Catalysis: A Transfer Hydrocyanation Exhibiting High Kinetic Control
Bhawal, Benjamin N.,Ehinger, Christian,Morandi, Bill,Reisenbauer, Julia C.
supporting information, p. 10914 - 10920 (2020/07/13)
Reversible catalytic reactions operate under thermodynamic control, and thus, establishing a selective catalytic system poses a considerable challenge. Herein, we report a reversible transfer hydrocyanation protocol that exhibits high selectivity for the thermodynamically less favorable branched isomer. Selectivity is achieved by exploiting the lower barrier for C-CN oxidative addition and reductive elimination at benzylic positions in the absence of a cocatalytic Lewis acid. Through the design of a novel type of HCN donor, a practical, branched-selective, HCN-free transfer hydrocyanation was realized. The synthetically useful resolution of a mixture of branched and linear nitrile isomers was also demonstrated to underline the value of reversible and selective transfer reactions. In a broader context, this work demonstrates that high kinetic selectivity can be achieved in reversible transfer reactions, thus opening new horizons for their synthetic applications.
Sterically Demanding Oxidative Amidation of α-Substituted Malononitriles with Amines Using O2
Li, Jing,Lear, Martin J.,Hayashi, Yujiro
, p. 9060 - 9064 (2016/07/26)
An efficient amidation method between readily available 1,1-dicyanoalkanes and either chiral or nonchiral amines was realized simply with molecular oxygen and a carbonate base. This oxidative protocol can be applied to both sterically and electronically challenging substrates in a highly chemoselective, practical, and rapid manner. The use of cyclopropyl and thioether substrates support the radical formation of α-peroxy malononitrile species, which can cyclize to dioxiranes that can monooxygenate malononitrile α-carbanions to afford activated acyl cyanides capable of reacting with amine nucleophiles.
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
experimental part, p. 852 - 860 (2012/02/05)
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].
