- Hydrogen Bonding-Assisted Enhancement of the Reaction Rate and Selectivity in the Kinetic Resolution of d,l-1,2-Diols with Chiral Nucleophilic Catalysts
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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.).
- Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
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supporting information
p. 2778 - 2788
(2017/08/23)
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- Enantioselective Ethylation of Various Aldehydes Catalyzed by Readily Accessible Chiral Diols
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Four chiral C2-symmetric diols were synthesized in a straightforward three-step reaction and demonstrated excellent enantioselectivities and good overall yields. Their catalytic activities were examined via the addition of diethylzinc to various aldehydes. The enantioselective addition of diethylzinc to 2-methoxybenzaldehyde gave the corresponding chiral secondary alcohol with high yields (up to 95%) and moderate to good enantiomeric excess (up to 88%). All synthesized ligands were evaluated in the addition of diethylzinc to various aldehydes in the presence of an additional metal such as Ti(IV) complexes. Chirality 28:593–598, 2016.
- G?k, Ya?ar,Kili?arslan, Seda,G?k, Halil Zeki,Karayi?it, ?lker ümit
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p. 593 - 598
(2016/08/27)
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- Stereoselective synthesis of optically active hydrobenzoins via asymmetric hydrogenation of benzils with Ru(OTf)(TsDPEN)(I·6- cymene) as the pre-catalyst
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Optically active hydrobenzoins are very important building blocks for further derivation of biologically active complexes, natural products, and pharmaceutical compounds. In this paper, A practical approach has been developed for asymmetric hydrogenation
- Huang, Xiaofei,Li, Naikai,Geng, Zhicong,Pan, Fengfeng,Wang, Xingwang
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p. 2657 - 2663
(2013/01/15)
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- Enantioselective pinacol coupling reaction of aromatic aldehydes catalyzed by chiral vanadium complexes
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The asymmetric pinacol coupling of aromatic aldehydes by chiral salan-vanadium complexes as effective catalysts is reported. Chiral 1,2-diols were obtained with high diastereoselectivities (up to 90/10) and moderate to high enantioselectivities (up to 82%
- Sun, Jiangtao,Dai, Zhenya,Li, Changsi,Pan, Xu,Zhu, Chengjian
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experimental part
p. 3219 - 3221
(2010/01/11)
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- Lanthanitin: A chiral nanoball encapsulating 18 lanthanum ions by ferritin-like assembly
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(Figure Presented) A chiral supramolecule, obtained by self-assembly of 24 chiral ditopic carboxylate ligands, 18 La ions, and two carbonate anions, has been dubbed lanthanitin because of its structural resemblance to ferritin. The picture shows the molec
- Jeong, Kyung Seok,Kim, Young Shin,Kim, Yun Ju,Lee, Eunsung,Yoon, Ji Hye,Park, Won Hwa,Park, Young Woo,Jeon, Seung-Joon,Kim, Zee Hwan,Kim, Jaheon,Jeong, Nakcheol
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p. 8134 - 8138
(2008/02/12)
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- The modulation of face-face π-π Interactions in Lewis acid catalysis
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The enantiomeric excess observed for the exo-adduct from the Lewis acid catalysed Diels-Alder reaction between cyclopentadiene and methacrolein can be increased up to 21% by simple modification of the electronics of the aromatic ring in a series of stilbene-derived diol ligands, suggesting that the proposed face-face π-π interaction between the catalyst and the dienophile can be modulated by altering the electron density on the aromatic ring.
- Harris, Lisa D.,Jenkins, Robert L.,Tomkinson, Nicholas C.O.
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p. 1627 - 1629
(2007/10/03)
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- Synthesis of chiral self-assembling rhombs and their characterization in solution, in the gas phase, and at the liquid-solid interface
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Chiral, enantiopure metallo-supramolecular rhombs self-assemble in solution through coordination of bis-pyridyl-substituted ligands with (en)M(NO 3)2 (en = ethylenediamine, M = PdII, Pt II). Characterization by
- Jeong, Kyung Seok,Kim, Sun Young,Shin, Ueon-Sang,Kogej, Michael,Hai, Nguyen T. M.,Broekmann, Peter,Jeong, Nakcheol,Kirchner, Barbara,Reiher, Markus,Schalley, Christoph A.
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p. 17672 - 17685
(2007/10/03)
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- On the paradox of TiCl4 reducing power: Pinacol coupling and two-carbon homologation of carbonyl compounds
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TiCl4/DIPEA/CH2Cl2 reducing system promotes pinacol coupling and/or reduction to alcohol of aromatic aldehydes and carbonyl compounds activated towards reduction by an electron withdrawing group. In addition, bis homologation of these substrates is observed. An inner-sphere electron transfer from TiCl4 to DIPEA accounts for the products distribution.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 1825 - 1827
(2007/10/03)
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- Enantioselective pinacol coupling of aldehydes mediated and catalyzed by chiral titanium complexes
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equation presented Starting from easily available chiral Schiff bases, a straightforward synthesis of air-stable titanium(IV) complexes was devised. Asymmetric pinacol coupling of aromatic aldehydes mediated and catalyzed by the corresponding low valent complexes afforded the chiral diols with high yields and enantioselectivities up to 91%. ? Universite catholique de Louvain. ? Universite Paris-Sud.
- Bensari, Ahlem,Renaud, Jean-Luc,Riant, Olivier
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p. 3863 - 3865
(2007/10/03)
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