- Enantioselective reduction of α-substituted ketones mediated by the boronate ester TarB-NO2
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A facile and mild reduction procedure is reported for the preparation of chiral secondary alcohols prepared from α-substituted ketones using sodium borohydride and the chiral boronate ester (l)-TarB-NO2. Direct reduction of substituted ketones bearing Lewis basic heteroatoms generally provided secondary alcohols of only modest enantiomeric excess likely due to either competition between the target carbonyl and the functionalized sidechains at the Lewis acidic boron atom in TarB-NO2 or the added steric bulk of the α-sidechain. As an alternative method, these substrates were synthesized using TarB-NO2 via a two-step procedure involving the reduction of an α-halo ketone to a chiral terminal epoxide, followed by regioselective/regiospecific epoxide opening by various nucleophiles. This procedure provides access to a variety of functionalized secondary alcohols including β-hydroxy ethers, thioethers, nitriles, and amines with enantiomeric excesses of 94% and yields up to 98%.
- Eagon, Scott,Ball-Jones, Nicholas,Haddenham, Dustin,Saavedra, Jaime,Delieto, Cassandra,Buckman, Matthew,Singaram, Bakthan
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supporting information; experimental part
p. 6418 - 6421
(2010/12/30)
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- Asymmetric synthesis of β-dialkylamino alcohols by transfer hydrogenation of α-dialkylamino ketones
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Transfer hydrogenation of representative aryl and heteroaryl dialkylaminomethyl ketones with formic acid-triethylamine, catalyzed by RuCl[(R,R)-TsDPEN](η-p-cymene), produces the corresponding β-dialkylamino alcohols, 97-99% ee, in 50-73% yields. Asymmetric synthesis of (R)-macromerine, 98% ee, the cactus Coryphantha macromeris alkaloid, is also described.
- Kosmalski, Tomasz,Wojtczak, Andrzej,Zaidlewicz, Marek
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experimental part
p. 1138 - 1143
(2009/09/27)
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- Synthesis and Biological activity of kappa opioid receptor agonists. Part 2: Preparation of 3-aryl-2-pyridone analogues generated by solution- and solid-phase parallel synthesis methods
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New analogues of the previously described 3-aryl pyridone KOR agonists have been synthesised by parallel synthetic methods, both in solution- and with solid-phase chemistry, making use of the well known and versatile Mitsunobu, Suzuki and Buchwald reactions. Opioid receptor binding data for the compounds produced is reported.
- Semple, Graeme,Andersson, Britt-Marie,Chhajlani, Vijay,Georgsson, Jennie,Johansson, Magnus J.,Rosenquist, Asa,Swanson, Lars
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p. 1141 - 1145
(2007/10/03)
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- Boranes in Synthesis. 2. Asymmetric Synthesis of β-Amino Alcohols. A Facile Conversion of 2-Amino Acetophenones to the Corresponding β-Amino Alcohols in High Enantiomeric Purity
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The asymmetric reduction of 2-amino acetophenones with Ipc2BH or Ipc2BCl at -78 deg C, yields the corresponding β-amino alcohols in good to excellent yields.Although only modest (12-45percent ee) enantiomeric excesses were obtained with Ipc2BH, 75-99perce
- Beardsley, David A.,Fisher, Gary B.,Goralski, Christian T.,Nicholson, Lawrence W.,Singaram, Bakthan
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p. 1511 - 1514
(2007/10/02)
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- Studies on the Oxidation of Enamines with Molecular Oxygen. III Oxidation of Some Amino Styrenes
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In the oxidation of the amino styrenes 1a - 1j only products of the oxidative attack at the C=C double bond and hydrolysis products are obtained.Aprotic dipolar solvents and the addition of molecular sieve 5A promote the oxygen uptake.The addition of hydroquinone to the oxidation system does not influence the rate of oxygen absorption or the yields of the oxidation products.
- Blau, K.,Burgemeister, I.,Grasnick, J.,Voerckel, V.
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p. 455 - 466
(2007/10/02)
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