- Dehydrogenative alcohol coupling and one-pot cross metathesis/dehydrogenative coupling reactions of alcohols using Hoveyda-Grubbs catalysts
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In this study,in situformed ruthenium hydride species that were generated from Grubbs type catalysts are used as efficient catalysts for dehydrogenative alcohol coupling and sequential cross-metathesis/dehydrogenative coupling reactions. The selectivity of Grubbs first generation catalysts (G1) in dehydrogenative alcohol coupling reactions can be tuned for the ester formation in the presence of weak bases, while the selectivity can be switched to the β-alkylated alcohol formation using strong bases. The performance of Hoveyda-Grubbs 2nd generation catalyst (HG2) was improved in the presence of tricyclohexylphosphine for the selective synthesis of ester derivatives with weak and strong bases in quantitative yields. Allyl alcohol was used as self and cross-metathesis substrate for the HG2 catalyzed sequential cross-metathesis/dehydrogenative alcohol coupling reactions to obtain γ-butyrolactone and long-chain ester derivatives in quantitative yields.
- ?zer, Halenur,Arslan, Dilan,?ztürk, Bengi ?zgün
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p. 5992 - 6000
(2021/04/12)
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- New strategy for production of primary alcohols from aliphatic olefins by tandem cross-metathesis/hydrogenation
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Primary alcohols are widely used in industry as solvents and precursors of detergents. The classic methods for hydration of terminal alkenes always produce the Markovnikov products. Herein, we reported a reliable approach to produce primary alcohols from terminal alkenes combining with biomass-derived allyl alcohol by tandem cross-metathesis/hydrogenation. A series of primary alcohol with different chain lengths was successfully produced in high yields (ca. 90percent). Computational studies revealed that self-metathesis and hydrogenation of substrates are accessible but much slower than cross-metathesis. This new methodology represents a unique alternative to primary alcohols from terminal alkenes.
- Jia, Ruilong,Zuo, Zhijun,Li, Xu,Liu, Lei,Dong, Jinxiang
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supporting information
p. 1525 - 1529
(2019/11/11)
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- Catalytic hydrosilylation of ketones using a Co/Zr heterobimetallic complex: Evidence for an unusual mechanism involving ketyl radicals
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The tris(phosphinoamide)-linked heterobimetallic Co/Zr complex (THF)Zr(MesNPiPr2)3CoN2 (1) has been investigated as a catalyst for the hydrosilylation of ketones with PhSiH 3. Catalytic activity superior to monometallic Co or Zr analogues has been observed, demonstrating the importance of cooperative reactivity between Co and Zr. Upon examining stoichiometric reactions, complex 1 was found to be unreactive toward PhSiH3, implying that the mechanism diverges from the typical Chalk-Harrod-type hydrosilylation pathway. In contrast, 1 reacts readily with ketones, and in the case of benzophenone, a radical coupling product [(Ph2CO)Zr(MesNPiPr2) 3CoN2]2 (3) was isolated, implying the intermediacy of a Zr-bound ketyl radical fragment. A radical-based hydrosilylation mechanism is proposed involving hydrogen atom transfer from PhSiH3 to the Zr-bound ketyl-radical.
- Zhou, Wen,Marquard, Seth L.,Bezpalko, Mark W.,Foxman, Bruce M.,Thomas, Christine M.
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p. 1766 - 1772
(2013/05/08)
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- Selectivity in the addition reactions of organometallic reagents to aziridine-2-carboxaldehydes: The effects of protecting groups and substitution patterns
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Good to excellent stereoselectivity has been found in the addition reactions of Grignard and organozinc reagents to N-protected aziridine-2-carboxaldehydes. Specifically, high syn selectivity was obtained with benzyl-protected cis, tert-butyloxycarbonyl-protected trans, and tosyl-protected 2,3-disubstituted aziridine-2-carboxaldehydes. Furthermore, rate and selectivity effects of ring substituents, temperature, solvent, and Lewis acid and base modifiers were studied. The diastereomeric preference of addition is dominated by the substrate aziridines' substitution pattern and especially the electronic character and conformational preferences of the nitrogen protecting groups. To help rationalize the observed stereochemical outcomes, conformational and electronic structural analyses of a series of model systems representing the various substitution patterns have been explored by density functional calculations at the B3LYP/6-31G* level of theory with the SM8 solvation model to account for solvent effects. Grignard and bear it: Good to excellent stereoselectivity is reported for the addition reactions of Grignard and organozinc reagents to N-protected aziridine-2-carboxaldehydes (see scheme). High syn selectivity was obtained with benzyl-protected cis, tert-butyloxycarbonyl-protected trans, and tosyl-protected 2,3-disubstituted aziridine-2-carboxaldehydes. Copyright
- Kulshrestha, Aman,Schomaker, Jennifer M.,Holmes, Daniel,Staples, Richard J.,Jackson, James E.,Borhan, Babak
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p. 12326 - 12339
(2011/12/15)
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- Properties and tissue distribution of a novel aldo-keto reductase encoding in a rat gene (Akr1b10)
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A recent rat genomic sequencing predicts a gene Akr1b10 that encodes a protein with 83% sequence similarity to human aldo-keto reductase (AKR) 1B10. In this study, we isolated the cDNA for the rat AKR1B10 (R1B10) from rat brain, and examined the enzymatic properties of the recombinant protein. R1B10 utilized NADPH as the preferable coenzyme, and reduced various aldehydes (including cytotoxic 4-hydroxy-2-hexenal and 4-hydroxy- and 4-oxo-2-nonenals) and α-dicarbonyl compounds (such as methylglyoxal and 3-deoxyglucosone), showing low Km values of 0.8-6.1μM and 3.7-67μM, respectively. The enzyme also reduced glyceraldehyde and tetroses (Km=96-390μM), although hexoses and pentoses were inactive and poor substrates, respectively. Among the substrates, 4-oxo-2-nonenal was most efficiently reduced into 4-oxo-2-nonenol, and its cytotoxicity against bovine endothelial cells was decreased by the overexpression of R1B10. R1B10 showed low sensitivity to aldose reductase inhibitors, and was activated to approximately two folds by valproic acid, and alicyclic and aromatic carboxylic acids. The mRNA for R1B10 was expressed highly in rat brain and heart, and at low levels in other rat tissues and skin fibroblasts. The results suggest that R1B10 functions as a defense system against oxidative stress and glycation in rat tissues.
- Endo, Satoshi,Matsunaga, Toshiyuki,Kuragano, Tsukasa,Ohno, Satoshi,Kitade, Yukio,Tajima, Kazuo,El-Kabbani, Ossama,Hara, Akira
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experimental part
p. 230 - 237
(2011/10/30)
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- Synthesis of α,α′-disubstituted linear ethers by an intermolecular nicholas reaction - Application to the synthesis of (+)-cis/-trans-lauthisan and (+)-cis/(+)-trans-obtusan
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A new and efficient methodology to prepare α,α'-disubstituted linear ethers through an intermolecular Nicholas reaction (interNR) is described. cis-2,8-Disubstituted oxocanes, cis-2,9-disubstituted oxonanes, their trans isomers, and their parent unsaturat
- Ortega, Nuria,Martin, Tomas,Martin, Victor S.
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scheme or table
p. 554 - 563
(2009/09/06)
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- Triethylborane-mediated hydrogallation and hydroindation: Novel access to organogalliums and organoindiums
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Hydrogallation of carbon-carbon multiple bonds proceeds in the presence of triethylborane as a radical initiator. Several functionalities do not interfere with this reaction. Resulting alkenyl- and alkylgallium species can be trapped by several electrophiles. Highly regioselective radical addition of an indium hydride reagent to alkynes is also achieved. Various functionalities are tolerant under the reaction conditions. The reaction proceeds with complete anti stereoselectivity. Alkenylindiums obtained via hydroindation can be employed for the following cross-coupling reaction with aryl halides in one pot.
- Takami, Kazuaki,Mikami, Satoshi,Yorimitsu, Hideki,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 6627 - 6631
(2007/10/03)
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