115889-24-2Relevant academic research and scientific papers
A practical stereoselective synthesis of chiral hydrobenzoins via asymmetric transfer hydrogenation of benzils
Murata, Kunihiko,Okano, Kazuya,Miyagi, Miwa,Iwane, Hiroshi,Noyori, Ryoji,Ikariya, Takao
, p. 1119 - 1121 (1999)
(matrix presented) Asymmetric reduction of benzil with RuCl[(S,S)-Tsdpen)(η6-p-cymene) in a mixture of formic acid and triethylamine proceeds with a substrate/ catalyst molar ratio of 1000-2000 to give (R,R)-hydrobenzoin quantitatively with high diastereomeric (97% de) and enantiomeric purities (>99% ee), in which the benzoin intermediate with a chirally labile stereogenic center is converted to one major stereoisomer, (R,R)-product, via dynamic kinetic resolution.
Isothiourea-Catalysed Sequential Kinetic Resolution of Acyclic (±)-1,2-Diols
Greenhalgh, Mark D.,Harrer, Siegfried,Neyyappadath, Rifahath M.,Smith, Andrew D.
supporting information, p. 1555 - 1560 (2019/08/07)
The isothiourea-catalysed acylative kinetic resolution of a range of acyclic (±)-1,2-diols using 1 molpercent of catalyst under operationally simple conditions is reported. Significantly, the bifunctional nature of (±)-1,2-diols was exploited in a sequential double kinetic resolution, in which both kinetic resolutions operate synergistically to provide access to highly enantioenriched products. The principles that underpin this process are discussed, and selectivity factors for the individual kinetic resolution steps are reported in a model system.
Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
supporting information, p. 2778 - 2788 (2017/08/23)
An extremely efficient acylative kinetic resolution of d,l-1,2-diols in the presence of only 0.5 mol% of binaphthyl-based chiral N,N-4-dimethylaminopyridine was developed (selectivity factor of up to 180). Several key experiments revealed that hydrogen bonding between the tert-alcohol unit(s) of the catalyst and the 1,2-diol unit of the substrate is critical for accelerating the rate of monoacylation and achieving high enantioselectivity. This catalytic system can be applied to a wide range of substrates involving racemic acyclic and cyclic 1,2-diols with high selectivity factors. The kinetic resolution of d,l-hydrobenzoin and trans-1,2-cyclohexanediol on a multigram scale (10 g) also proceeded with high selectivity and under moderate reaction conditions: (i) very low catalyst loading (0.1 mol%); (ii) an easily achievable low reaction temperature (0 °C); (iii) high substrate concentration (1.0 M); and (iv) short reaction time (30 min). (Figure presented.).
Catalytic enantioselective allyl- and crotylboration of aldehydes using chiral diol·SnCl4 complexes. Optimization, substrate scope and mechanistic investigations
Rauniyar, Vivek,Zhai, Huimin,Hall, Dennis G.
supporting information; experimental part, p. 8481 - 8490 (2009/02/02)
We report a novel class of C2-symmetric chiral diols derived from the hydrobenzoin skeleton. The combination of these diols with SnCl 4 under Yamamoto's concept of Lewis acid assisted Bronsted acidity (LBA catalysis) leads to high levels of asymmetric induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate units in >95:5 dr and up to 98:2 er. The X-ray crystal structure of the optimal diol·SnCl4 complex, Vivol (4m)·SnCl 4, unambiguously shows the Bronsted acidic character of this LBA catalyst and its highly dissymmetrical environment. Further controls have ruled out a possible boron transesterification mechanism with the chiral diol and point to LBA catalyst-derived activation of the pinacol allylic boronates 1. Due to slow dissociation of the diol·SnCl4 complex, a small excess of diol is required in order to suppress a competing racemic cycle catalyzed by free SnCl4.
Scandium-bipyridine-catalyzed, enantioselective alcoholysis of meso-epoxides
Tschoep, Andreas,Marx, Andreas,Sreekanth, Anakallil R.,Schneider, Christoph
, p. 2318 - 2327 (2008/02/08)
The scandium-bipyridine-catalyzed ring-opening of meso-epoxides with aliphatic alcohols has been studied. Aromatic epoxides were ring-opened with >90 % ee furnishing valuable 1,2-diol monoethers in typically good yields whereas aliphatic epoxides gave ris
Catalytic enantioselective and catalyst-controlled diastereofacial- selective additions of allyl- and crotylboronates to aldehydes using chiral Bronsted acids
Rauniyar, Vivek,Hall, Dennis G.
, p. 2426 - 2428 (2007/10/03)
(Chemical Equation Presented) Towards the ideal: A chiral diol-SnCl 4 complex is applied to the allylboration of aldehydes (see scheme). This approach highlights the use of chiral Bronsted acid catalysis in the development of an ideal method for the allylation of aldehydes which would display high diastereo- and enantioselectivity, wide substrate scope, and high practicality (ease of use, low cost, and low environmental impact).
Scandium-bipyridine-catalyzed enantioselective addition of alcohols and amines to meso-epoxides
Schneider, Christoph,Sreekanth, Anakallil R.,Mai, Enzo
, p. 5691 - 5694 (2007/10/03)
A winning combination of metal and ligand: The catalyst formed in situ from Sc(OTf)3 and bipyridine 1 (10 mol%) mediates the alcoholysis and aminolysis of Mieso-epoxides in high enantioselectivities and furnishes valuable chiral 1,2-diol monoethers 2 and 1,2-amino alcohols 3 as products (PMB = para-methoxybenzyl).
The crystallographic structure of a Lewis acid-assisted chiral Bronsted acid as an enantioselective protonation reagent for silyl enol ethers
Ishihara, Kazuaki,Nakashima, Daisuke,Hiraiwa, Yukihiro,Yamamoto, Hisashi
, p. 24 - 25 (2007/10/03)
It is difficult to control the enantioselectivity in the protonation of silyl enol ethers with simple chiral Bronsted acids, mainly due to bond flexibility between the proton and its chiral counterion, the orientational flexibility of the proton, and the fact that the proton sources available are limited to acidic compounds such as chiral carboxylic acids. To overcome these difficulties, we have developed a Lewis acid-assisted chiral Bronsted acid (LBA) system. The coordination of Lewis acids with Bronsted acids restricts the orientation of protons and increases their acidity. Optically active binaphthol (BINOL) derivative·SnCl4 complexes are very effective as enantioselective protonation reagents for silyl enol ethers. However, their exact structures have not yet been determined. We describe here optically active 1,2-diarylethane-1,2-diol derivative·SnCl4 as a new type of LBA for the enantioselective protonation as well as its crystallographic structure. A variety of optically active 1,2-diarylethane-1,2-diols could be readily prepared by asymmetric syn-dihydroxylation. This is a great advantage over BINOL for the flexible design of a new LBA. The most significant finding is that we were able to specify the conformational direction of the H-O bond of LBA, which has some asymmetric inductivity, by X-ray diffraction analysis. The stereochemical course in the enantioselective protonation of silyl enol ethers using LBA would be controlled by a linear OH/π interaction with an initial step. The absolute stereopreference in enantioselective reactions using BINOL·SnCl4 can also be explained in terms of this uniformly mechanistic interpretation. Copyright
Enantioselective reactions of α-methoxybenzyllithium generated by t-BuLi/chiral bis(oxazoline) complex with aldehydes
Tomooka, Katsuhiko,Wang, Lan-Fang,Komine, Nobuyuki,Nakai, Takeshi
, p. 6813 - 6816 (2007/10/03)
The title reaction is shown to afford the corresponding 1,2-diol monomethyl ethers in moderate-to-high levels of % ee (up to 98%) and % de (up to 90% anti), depending markedly on the aldehyde reactivity. The origin of the enantioselectivity is discussed i
Enantioselective catalysis CXXI [1]: Chiral phosphane ligands with additional oxygen functionalities
Brunner,Ru?ckert
, p. 339 - 354 (2007/10/03)
New optically active phosphane ligands with additional ether and hydroxy functionalities were synthesied and used as sources of enantio-selectivity in the Ni-catalyzed cross coupling reaction of 1-phenylethyl Grignard and vinylbromide and in the Pd-catalyzed allylation of 1,5-dimethylbarbituric acid with allyl acetate.
