88424-61-7Relevant academic research and scientific papers
Design of optically active hydroxamic acids as ligands in vanadium- catalyzed asymmetric epoxidation
Hoshino, Yujiro,Murase, Noriaki,Oishi, Masataka,Yamamoto, Hisashi
, p. 1653 - 1658 (2000)
New optically active hydroxamic acids bearing a 1,1'-binaphthyl group were prepared as ligands in a vanadium-catalyzed asymmetric epoxidation. The feature of these hydroxamic acids is a sterically hindered ligand. The asymmetric epoxidation with good selectivity and reactivity can be established by using VO(O-i-Pr)3 (5 mol%) and a small excess amount of ligand (7.5 mol%) with triphenylmethyl hydroperoxide (TrOOH) in toluene at - 20 °C. Disubstituted allyl alcohols were epoxidized more rapidly than mono- or tri-substituted allyl alcohols, and were obtained in good to high enantioselectivities (48 - 94%ee). The transition state based on X-ray crystal structure of 1e is discussed.
ASYMETRIC EPOXIDATION MODELS: AN ALKYL HYDROPEROXIDE DEPENDENT CHANGE IN MECHANISM
Hawkins, Joel M.,Sharpless, K. Barry
, p. 2825 - 2828 (1987)
Titanium(IV)-pyridinediol complex 5 was studied as a model for titanium-tartarate asymmetric epoxidation catalysts.The sign of induction depended on the alkyl group of the alkyl hydroperoxide oxidant.Trityl hydroperoxide gave 64percent ee in the direction predicted by the model.
Asymmetric epoxidation of allylic alcohols catalyzed by vanadium-binaphthylbishydroxamic acid complex
Noji, Masahiro,Kobayashi, Toshihiro,Uechi, Yuria,Kikuchi, Asami,Kondo, Hisako,Sugiyama, Shigeo,Ishii, Keitaro
, p. 3203 - 3210 (2015/03/30)
A vanadium-binaphthylbishydroxamic acid (BBHA) complex-catalyzed asymmetric epoxidation of allylic alcohols is described. The optically active binaphthyl-based ligands BBHA 2a and 2b were synthesized from (S)-1,1'-binaphthyl-2,2'dicarboxylic acid and N-substituted-O-trimethylsilyl (TMS)-protected hydroxylamines via a one-pot, three-step procedure. The epoxidations of 2,3,3-trisubstituted allylic alcohols using the vanadium complex of 2a were easily performed in toluene with a TBHP water solution to afford (2R)-epoxy alcohols in good to excellent enantioselectivities.
Tungsten-catalyzed asymmetric epoxidation of allylic and homoallylic alcohols with hydrogen peroxide
Wang, Chuan,Yamamoto, Hisashi
supporting information, p. 1222 - 1225 (2014/02/14)
A simple, efficient, and environmentally friendly asymmetric epoxidation of primary, secondary, tertiary allylic, and homoallylic alcohols has been accomplished. This process was promoted by a tungsten-bishydroxamic acid complex at room temperature with the use of aqueous 30% H2O2 as oxidant, yielding the products in 84-98% ee.
Vanadium-catalyzed asymmetric epoxidation of allylic alcohols in water
Malkov, Andrei V.,Czemerys, Louise,Malyshev, Denis A.
experimental part, p. 3350 - 3355 (2009/09/26)
Asymmetric V-catalyzed epoxidation of allylic alcohols can be carried out in water with chiral ligands, which incorporate sulfonamide and hydroxamic acid fragments. Furthermore, the reaction, notorious for its ligand-deceleration effect, in water turned into the ligand-accelerated process. By using this aqueous protocol, a range of allylic alcohols were epoxidized with up to 94% ee.
Development and application of versatile bis-hydroxamic acids for catalytic asymmetric oxidation
Barlan, Allan U.,Zhang, Wei,Yamamoto, Hisashi
, p. 6075 - 6087 (2008/02/03)
In this article, we describe the development and preliminary results of our new designed C2-symmetric bis-hydroxamic acid (BHA) ligands and the application of the new ligands for vanadium-catalyzed asymmetric epoxidation of allylic alcohols as well as homoallylic alcohols. From this success we demonstrate the versatile nature of BHA in the molybdenum catalyzed asymmetric oxidation of unfunctionalized olefins and sulfides.
Vanadium-catalyzed asymmetric epoxidation: Proline-derived hydroxamic acids revisited
Bourhani, Za?naba,Malkov, Andrei V.
, p. 3525 - 3528 (2007/10/03)
Structural features of ligands and substrates affecting enantioselectivity in vanadium(V)-catalyzed epoxidation of allylic alcohols were investigated. For the hydroxamic acid ligands derived from arylhydroxylamines, 2-aryl-substituted allylic alcohols eme
Catalytic asymmetric epoxidation
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Page/Page column 13, (2010/02/12)
The present invention relates to the synthesis of chiral epoxides via a catalytic asymmetric oxidation of olefins. Additionally, the methodology provides a method of asymmetrically oxidizing sulfides and phosphines. This asymmetric oxidation employs a catalyst system composed of a metal and a chiral bishydroxamic acid ligand, which, in the presence of a stoichiometric oxidation reagent, serves to asymmetrically oxidize a variety of substrates.
Enantioselective epoxidation of allylic alcohols by a chiral complex of vanadium: An effective controller system and a rational mechanistic model
Zhang, Wei,Basak, Arindrajit,Kosugi, Yuji,Hoshino, Yujiro,Yamamoto, Hisashi
, p. 4389 - 4391 (2007/10/03)
(Chemical Equation Presented) Bishydroxamic acid derivatives are used as ligands for a vanadium catalyst in the preparation of epoxy alcohols (see scheme). The methodology uses aqueous tert-butyl hydroperoxide (TBHP) as an achiral oxidant, low catalyst loading, low reaction temperatures (0°C to room temperature), and simple workup procedures. The reaction is applied to the kinetic resolution of a secondary allylic alcohol and the preparation of small epoxy alcohols. R1, R2, R3: alkyl, aryl, H.
Control of enantioselectivity through a hydrogen-bonded template in the vanadium(V)-catalyzed epoxidation of allylic alcohols by optically active hydroperoxides
Adam, Waldemar,Beck, Albert K.,Pichota, Arkadius,Saha-Moeller, Chantu R.,Seebach, Dieter,Vogl, Nadine,Zhang, Rui
, p. 1355 - 1361 (2007/10/03)
The vanadium(V)-catalyzed asymmetric epoxidation of primary allylic alcohols by the optically active TADDOL-derived hydroperoxide as the asymmetric controller provides the corresponding (R)-epoxides in up to 72% ee. From this mechanistic study we conclude
