- Chemoselective and Site-Selective Reductions Catalyzed by a Supramolecular Host and a Pyridine-Borane Cofactor
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Supramolecular catalysts emulate the mechanism of enzymes to achieve large rate accelerations and precise selectivity under mild and aqueous conditions. While significant strides have been made in the supramolecular host-promoted synthesis of small molecules, applications of this reactivity to chemoselective and site-selective modification of complex biomolecules remain virtually unexplored. We report here a supramolecular system where coencapsulation of pyridine-borane with a variety of molecules including enones, ketones, aldehydes, oximes, hydrazones, and imines effects efficient reductions under basic aqueous conditions. Upon subjecting unprotected lysine to the host-mediated reductive amination conditions, we observed excellent ?-selectivity, indicating that differential guest binding within the same molecule is possible without sacrificing reactivity. Inspired by the post-translational modification of complex biomolecules by enzymatic systems, we then applied this supramolecular reaction to the site-selective labeling of a single lysine residue in an 11-amino acid peptide chain and human insulin.
- Morimoto, Mariko,Cao, Wendy,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
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supporting information
p. 2108 - 2114
(2021/02/06)
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- Method of preparing 2-methyl-1, 3-pentadiene
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The invention discloses a method of preparing 2-methyl-1, 3-pentadiene, which comprises the following steps: by using isobutene and acetaldehyde as raw materials, carrying out a Prins reaction to prepare 4-methyl-3-ene-2-pentanol and 4-methyl-4-ene-2-pentanol, and carrying out a dehydration reaction to prepare 2-methyl-1, 3-pentadiene. The whole reaction process is mild in condition, low in cost,low in energy consumption and less in three wastes, and the total yield of the 2-methyl-1, 3-pentadiene after the two-step reaction is higher than the yield of the 2-methyl-1, 3-pentadiene prepared byadopting 2-methyl-2, 4-pentanediol dehydration in a traditional process.
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Paragraph 0076-0104
(2020/04/17)
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- Synthesis of antimalarial trioxanes via continuous photo-oxidation with 1O2 in supercritical CO2
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The oxidation of an allylic alcohol to its hydroperoxides represents a key step in the synthesis of a series of spirobicyclic, antimalarial trioxanes. Herein, we investigate the continuous photo-oxidation of an allylic alcohol with 1O2 in scCO2, as a 'green' alternative to conventional methods, and examine the remaining two steps in the synthesis of antimalarial trioxanes from readily available starting materials.
- Hall, Jessica F. B.,Bourne, Richard A.,Han, Xue,Earley, James H.,Poliakoff, Martyn,George, Michael W.
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supporting information
p. 177 - 180
(2013/02/26)
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- Rhodium(I) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks
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Novel rhodium(i) complexes with N-heterocyclic carbenes bearing a 2,3,4,5-tetraphenylphenyl and its higher dendritic frameworks were synthesized and the complexes were used as catalysts in rhodium-catalyzed hydrosilylation of α,β-unsaturated ketones to show high 1,4-adduct selectivity. The Royal Society of Chemistry.
- Sato, Hiromichi,Fujihara, Tetsuaki,Obora, Yasushi,Tokunaga, Makoto,Kiyosu, Junya,Tsuji, Yasushi
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p. 269 - 271
(2007/10/03)
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- Process for dehydrating 2-methylpentane-2,4-diol
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A process for dehydrating 2-methylpentanediol-2,4 to a mixture of 2-methyl-1,3-pentadiene and 4-methyl-1,3-pentadiene at elevated temperature in the presence of an acid catalyst using a polyglycol ether as a heat carrier, wherein a polyglycol ether containing from 80 to 100% by weight of a polyethylene glycol dimethyl ether of the formula CH3(OCH2CH2)nOCH3 where n=2-8 and from 0 to 20% by weight of a polyethylene glycol monomethyl ether of the formula CH3(OCH2CH2)nOH where n=2-8 based in each case on the total mass of polyglycol ether, is used.
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Page/Page column 2-3
(2008/06/13)
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- Selective hydrogenation of α,β-unsaturated ketones to α,β-unsaturated alcohols on gold-supported catalysts
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The liquid-phase reduction of α,β-unsaturated ketones [trans,4-phenyl,3-buten,2-one (benzalacetone C6H5CHCHCOCH3), 4 -methyl,3-penten,2-one (CH3) 2CCHCOCH3, and 3-penten,2-one CH3CHCHCOCH 3] to the corresponding α,β-unsaturated alcohols has been investigated on gold-supported catalysts. Au/Fe2O3 and Au/Al2O3 have been prepared by coprecipitation and deposition-precipitation. The catalytic behavior of a Au/Fe2O 3 "reference" catalyst supplied by the World Gold Council has been also investigated. In the hydrogenation of benzalacetone and 4-methyl,3-penten,2-one on the "homemade" Au/Fe2O 3 catalysts the unsaturated alcohol is the main reaction product. Chemoselectivity higher than 60% was achieved. On Au/Al2O 3, the selectivity is 10%. It is noteworthy that within the gold supported on iron oxide samples, the reference catalyst shows the lowest selectivity toward the formation of the unsaturated alcohol. In the hydrogenation of 3-penten,-2-one on the homemade Au/Fe2O 3, the saturated ketone is the main reaction product and the selectivity toward the formation of the unsaturated alcohol is 15% at conversion 90%. It is likely that the absence of bulky substituents on the conjugated CC double bond favors its adsorption on the catalytic sites, leading to the formation of the saturated carbonyl compounds as the main reaction product. A detailed characterization of the investigated catalysts by TEM and XRD is also reported.
- Milone,Ingoglia,Pistone,Neri,Frusteri,Galvagno
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p. 348 - 356
(2007/10/03)
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- ORGANOMANGANESE (II) REAGENTS XVIII: COPPER-CATALYZED 1,4-ADDITION OF ORGANOMANGANESE CHLORIDE COMPOUNDS TO CONJUGATED ETHYLENIC ALDEHYDES.
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Organomanganese chlorides react with β-mono or β,β-bisubstituted α,β-ethylenic aldehydes in the presence of a catalytic amount of copper chloride to give good yields of 1,4-addition products in THF at -30 deg C.
- Cahiez, Gerard,Alami, Mouad
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p. 7365 - 7368
(2007/10/02)
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- Intramolecular Activation of a N-Methyl C-H Bond by an Electron Rich Iridium Centre: a Novel Chemoselective Reduction Catalyst
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The iridium complex > formed by intramolecular C-H oxidative addition, as shown by X-ray analysis, behaves as a chemoselective catalyst in hydrogen transfer reduction of α,β-unsaturated ketones to unsaturated alcohols.
- Farnetti, Erica,Nardin, Giorgio,Graziani, Mauro
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p. 1264 - 1265
(2007/10/02)
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- Hydride-Mediated Homogeneous Catalysis. Catalytic Reduction of α,β-Unsaturated Ketones Using 6 and H2
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Hydride-mediated reduction of α,β-unsaturated ketones catalytic in the hydride reagent is reported using 6 and molecular hydrogen.The reaction proceeds at room temperature and is highly regioselective, affording either the product of conjugate reduction or complete 1,4- and 1,2-reduction to the saturated alcohol, depending on reaction conditions.In the presence of excess phosphine, the process is homogeneous and chemoselective: isolated double bonds are not hydrogenated, even under forcing conditions.This novel catalytic reduction appears to proceed viathe heterolytic activation of molecular hydrogen by highly reactive copper(I) enolate and alkoxide intermediates.
- Mahoney, Wayne S.,Stryker, Jeffrey M.
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p. 8818 - 8823
(2007/10/02)
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- A MEERWEIN-PONNDORF-VERLEY TYPE REDUCTION OF α,β UNSATURATED KETONES TO ALLYLIC ALCOHOLS CATALYZED BY MgO
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Allylic alcohols are obtained with an unprecedented simple method by chemoselective hydrogen transfer reduction of α,β unsaturated ketones catalyzed by MgO.
- Kaspar, J.,Trovarelli, A.,Lenarda, M.,Graziani, M.
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p. 2705 - 2706
(2007/10/02)
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- SELECTIVE REDUCTION OF α,β-UNSATURATED KETONES WITH POTASSIUM TRIPHENYLBOROHYDRIDE
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Potassium triphenylborohydride is an excellent 1,4-reducing agent for acyclic enones and β-unsubstituted cyclohexenones, and shows a greater tendency for 1,4-reduction than K-Selectride for β-substituted cyclohexenones and aromatic enones.
- Kim, Kwan Eung,Park, Soo Bong,Yoon, Nung Min
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- AlPO4-Al2O3 PROMOTED CYCLODEHYDRATION OF DIOLS
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A convenient method for the preparation of cyclic ethers by distillation of diols over solid AlPO4-Al2O3 is presented.
- Costa, A.,Riego, J. M.
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p. 1373 - 1376
(2007/10/02)
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- Studies on the Autoxidation of Branched-chain Olefins. I. Autoxidation of 2-Methylalk-1-enes and 2-Methylalk-2-enes
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The products of the autoxidation of 2-methylpent-1-ene, 2-methylpent-2-ene, 2-methylhex-1-ene, 2-methylhex-2-ene, 2,4,4-trimethylpent-1-ene, and 2,4,4-trimethylpent-2-ene were analyzed by gas chromatography.The identification of the products corresponding to the individual peaks was possible by comparison with authentic substances or by preparative gaschromatographic separation and n.m.r.-spectroscopy of the isolated samples.In this way not only the epoxides and the products of the oxidative cleavage of the C=C double bond but also the allylic alcohols formed by LiAlH4-reduction of the oxidation mixtures could be identified and analyzed.From the results the compositions of the original oxidation mixtures were calculated.
- Bilas, W.,Hoebold, W.,Pritzkow, W.
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p. 125 - 141
(2007/10/02)
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- Metal Catalysis in Organic Reactions. 16. Conjugate Reduction of α,β-Unsaturated Ketones by Trialkylalane-Nickel Systems
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The reaction between triisobutylaluminum and α,β-unsaturated ketones, in pentane at room temperature, leads to products which correspond to 1,2-reduction and 1,2-addition processes.The extent of such reactions is dependent on both the structure of the enone and the reagent-to-substrate ratio.Under the same experimental conditions, bis(N-methylsalicylaldimine)nickel catalyzes the conjugate reduction of α,β-enones by triisobutylaluminum; acyclic and cyclic enones have been converted into the corresponding saturated ketones in good to excellent yields.The catalytic process is discussed in terms of a catalytic cycle involving a hydridonickel species.
- Caporusso, Anna Maria,Giacomelli, Giampaolo,Lardicci, Luciano
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p. 4640 - 4644
(2007/10/02)
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