20134-00-3Relevant articles and documents
Chiral-Substituted Poly-N-vinylpyrrolidinones and Bimetallic Nanoclusters in Catalytic Asymmetric Oxidation Reactions
Hao, Bo,Gunaratna, Medha J.,Zhang, Man,Weerasekara, Sahani,Seiwald, Sarah N.,Nguyen, Vu T.,Meier, Alex,Hua, Duy H.
supporting information, p. 16839 - 16848 (2017/01/10)
A new class of poly-N-vinylpyrrolidinones containing an asymmetric center at C5 of the pyrrolidinone ring were synthesized from l-amino acids. The polymers, particularly 17, were used to stabilize nanoclusters such as Pd/Au for the catalytic asymmetric oxidations of 1,3- and 1,2-cycloalkanediols and alkenes, and Cu/Au was used for C-H oxidation of cycloalkanes. It was found that the bulkier the C5 substituent in the pyrrolidinone ring, the greater the optical yields produced. Both oxidative kinetic resolution of (±)-1,3- and 1,2-trans-cycloalkanediols and desymmetrization of meso cis-diols took place with 0.15 mol % Pd/Au (3:1)-17 under oxygen atmosphere in water to give excellent chemical and optical yields of (S)-hydroxy ketones. Various alkenes were oxidized with 0.5 mol % Pd/Au (3:1)-17 under 30 psi of oxygen in water to give the dihydroxylated products in >93% ee. Oxidation of (R)-limonene at 25 °C occurred at the C-1,2-cyclic alkene function yielding (1S,2R,4R)-dihydroxylimonene 49 in 92% yield. Importantly, cycloalkanes were oxidized with 1 mol % Cu/Au (3:1)-17 and 30% H2O2 in acetonitrile to afford chiral ketones in very good to excellent chemical and optical yields. Alkene function was not oxidized under the reaction conditions. Mechanisms were proposed for the oxidation reactions, and observed stereo- and regio-chemistry were summarized.
Enzymatic resolution, desymmetrization, and dynamic kinetic asymmetric transformation of 1,3-cycloalkanediols
Fransson, Ann-Britt L.,Xu, Yongmei,Leijondahl, Karin,Baeckvall, Jan-E.
, p. 6309 - 6316 (2007/10/03)
An efficient desymmetrization of cis-1,3-cyclohexanediol to (1S,3R)-3-(acetoxy)-1-cyclohexanol ((R,S)-2a) was performed via Candida antarctica lipase B (CALB)-catalyzed transesterification, in high yield (up to 93%) and excellent enantioselectivity (ee's
The Regiochemistry and Stereochemistry of the Hydroboration of Allylsilanes
Fleming, Ian,Lawrence, Nicholas J.
, p. 3309 - 3326 (2007/10/02)
The hydroboration of a wide range of allylsilanes 3 and 5-21 is found to be generally regioselective for attachment of the boron to C-3 and hydrogen to C-2 of the allyl unit, and to be generally stereoselective in the sense 1, with attachment of the boron
Molecular Recognition and Stereoselectivity: Geometrical Requirements for the Multiple Hydrogen-Bonding Interaction of Diols with a Multidentate Polyhydroxy Macrocycle
Kikuchi, Yasuaki,Kato, Yasushi,Tanaka, Yasutaka,Toi, Hiroo,Aoyama, Yasuhiro
, p. 1349 - 1354 (2007/10/02)
Resorcinol-dodecanal cyclotetramer 1 in CDCl3 forms hydrogen-bonded, 1/1 complexes with cyclohexanediols as well as with 2,4-pentane- and 2,5-hexanediol as their open-chain analogues and cyclohexanol and cis- and trans-4-tert-butylcyclohexanol.The affinities to 1 of cyclic diols (K=(1.1-10) * 102 M-1 at 25 deg C) are significantly larger than those of open-chain diols (36-43 M-1) and monools (8-11 M-1).Those of regio- and stereoisomers of cyclohexanediol depend on the configuration (axial-equatorial > diequatorial) and relative positions (1,4 >> 1,2 > 1,3) of the two OH groups involved and decrease in the order cis-1,4 (K=1.04 * 103) > cis-1,2 (2.64 * 102) > trans-1,3 (1.81 * 102) > trans-1,4 (1.29 * 102) > cis-1,3 (1.24 * 102) > trans-1,2 (1.06 * 102 M-1); the stereoselectivities are thus cis-1,4/trans-1,4 = 8.0, cis-1,2/trans-1,2 = 2.5, and trans-1,3/cis-1,3 = 1.5.The selectivities in the diol binding are discussed in terms of multiple hydrogen bonding of diol and 1.The relatively large binding constant (K) for cis-1,4-diol with one axial and one equatorial OH group is attributed to an effective and simultaneous two-point hydrogen bonding of the two OH groups with two adjacent binding sites of 1 as a multidentate host.
