- Rhodium-catalyzed synthesis of imines and esters from benzyl alcohols and nitroarenes: Change in catalyst reactivity depending on the presence or absence of the phosphine ligand
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The [Rh(COD)Cl]2/xantphos/Cs2CO3 system efficiently catalyzes the reductive N-alkylation of aryl nitro compounds with alcohols by a borrowing-hydrogen strategy to afford the corresponding imine products in good to excellent yields. In the absence of xantphos, the [Rh(COD)Cl]2/Cs2CO3 catalytic system behaves as an effective catalyst for the dehydrogenative coupling of alcohols to esters, with nitrobenzene as a hydrogen acceptor. The reactivity of the rhodium catalytic system can be easily manipulated to selectively afford the imine or ester.
- Song, Taemoon,Park, Ji Eun,Chung, Young Keun
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p. 4197 - 4203
(2018/04/14)
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- Manganese Pincer Complexes for the Base-Free, Acceptorless Dehydrogenative Coupling of Alcohols to Esters: Development, Scope, and Understanding
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Aliphatic PNP pincer-supported earth-abundant manganese(I) dicarbonyl complexes behave as effective catalysts for the acceptorless dehydrogenative coupling of a wide range of alcohols to esters under base-free conditions. The reaction proceeds under neat conditions, with modest catalyst loading and releasing only H2 as byproduct. Mechanistic aspects were addressed by synthesizing key species related to the catalytic cycle (characterized by X-ray structure determination, multinuclear (1H, 13C, 31P, 15N, 55Mn) NMR, infrared spectroscopy, inter alia), by studying elementary steps connected to the postulated mechanism, and by resorting to DFT calculations. As in the case of related ruthenium and iron PNP catalysts, the dehydrogenation results from cycling between the amido and amino-hydride forms of the PNP-Mn(CO)2 scaffold. For the dehydrogenation of alcohols into aldehydes, our results suggest that the highest energy barrier corresponds to the hydrogen release from the amino-hydride form, although its value is close to that of the outer-sphere dehydrogenation of the alcohol into aldehyde. This contrasts with the ruthenium and iron catalytic systems, where dehydrogenation of the substrate into aldehyde is less energy-demanding compared to hydrogen release from the cooperative metal-ligand framework.
- Nguyen, Duc Hanh,Trivelli, Xavier,Capet, Frédéric,Paul, Jean-Fran?ois,Dumeignil, Franck,Gauvin, Régis M.
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p. 2022 - 2032
(2017/08/14)
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- Acceptorless dehydrogenative coupling of alcohols catalysed by ruthenium PNP complexes: Influence of catalyst structure and of hydrogen mass transfer
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Base-free catalytic acceptorless dehydrogenative homo-coupling of alcohols to esters under neat conditions was investigated using a combined organometallic synthesis and kinetic modelling approach. The considered bifunctional ruthenium aliphatic PNP complexes are very active, affording TONs up to 15,000. Notably, gas mass transfer issues were identified, which allowed us to rationalize previous observations. Indeed, the reaction kinetics are limited by the rate of transfer from the liquid phase to the gas phase of the hydrogen co-produced in the reaction. Mechanistically speaking, this relates to the interconverting couple amido monohydride/amino bishydride. Overcoming this by switching into the chemical regime leads to an initial turnover frequency increase from about 2000 up to 6100?h?1. This has a significant impact when considering assessment of novel or reported catalytic systems in this type of reaction, as overlooking of these engineering aspects can be misleading.
- Zhang, Lei,Raffa, Guillaume,Nguyen, Duc Hanh,Swesi, Youssef,Corbel-Demailly, Louis,Capet, Frédéric,Trivelli, Xavier,Desset, Simon,Paul, Sébastien,Paul, Jean-Fran?ois,Fongarland, Pascal,Dumeignil, Franck,Gauvin, Régis M.
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p. 331 - 343
(2016/07/06)
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- Nematicidal activity of natural ester compounds and their analogues against pine wood nematode, bursaphelenchus xylophilus
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In this study, we evaluated the nematicidal activity of natural ester compounds against the pine wood nematode, Bursaphelenchus xylophilus, to identify candidates for the development of novel, safe nematicides. We also tested the nematicidal activity of synthesized analogues of these ester compounds to determine the structure-activity relationship. Among 28 ester compounds tested, isobutyl 2-methylbutanoate, 3-methylbutyl 2-methylbutanoate, 3-methylbutyl tiglate, 3-methyl-2-butenyl 2- methylbutanoate, and pentyl 2-methylbutanoate showed strong nematicidal activity against the pine wood nematode at a 1 mg/ mL concentration. The other ester compounds showed weak nematicidal activity. The LC50 values of 3-methylbutyl tiglate, isobutyl 2-methylbutanoate, 3-methylbutyl 2-methylbutanoate, 3-methyl-2-butenyl 2-methylbutanoate, and pentyl 2- methylbutanoate were 0.0218, 0.0284, 0.0326, 0.0402, and 0.0480 mg/mL, respectively. The ester compounds described herein merit further study as potential nematicides for pine wood nematode control.
- Seo, Seon-Mi,Kim, Junheon,Koh, Sang-Hyun,Ahn, Young-Joon,Park, Il-Kwon
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p. 9103 - 9108
(2015/03/14)
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- Efficient dimeric esterification of alcohols with NBS in water using l-proline as catalyst
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The L-proline-catalyzed oxidation of aliphatic primary alcohols with N-bromosuccimide (NBS) in water at room temperature to afford the corresponding dimeric esters in good to excellent yields was described. This pathway of dimeric esterification was proved to be very simple and environmentally friendly.
- Liu, Xiuhong,Wu, Jun,Shang, Zhicai
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experimental part
p. 75 - 83
(2011/11/05)
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- PROCESS FOR PREPARING AMIDES FROM ALCOHOLS AND AMINES
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The present invention provides a process for preparing amides, by reacting a primary amine and a primary alcohol in the presence of a Ruthenium catalyst, to generate the amide and molecular hydrogen. According to the process of the invention, primary amines are directly acylated by equimolar amounts of alcohols to produce amides and molecular hydrogen (the only byproduct) in high yields and high turnover numbers. This reaction is catalyzed by a Ruthenium complex, which is preferably based on a dearomatized PNN-type ligand of formula A1 or precursors thereof of formulae A2 or A3. Use of diamines in the reaction leads to bis-amides, whereas with a mixed primary/secondary amine substrate, chemoselective acylation of the primary amine group occurs.
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Page/Page column 7-8; 11
(2009/05/28)
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- Esterification of aldehydes and alcohols with pyridinium hydrobromide perbromide in water
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The direct esterification of aldehydes and alcohols was carried out with pyridinium hydrobromide perbromide in water at room temperature. A variety of aldehydes were converted to respective ester derivatives with alcohols such as methanol, 1,2-ethanediol, 1,3-propanediol. Further, a variety of aliphatic alcohols were also converted to the corresponding Tishchenko-like dimeric esters in good yields under the same reaction conditions.
- Sayama, Shinsei,Onami, Tetsuo
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p. 2739 - 2745
(2007/10/03)
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- The role of functionalized phosphines in the hydrogenation of carboxylic acids in the presence of phosphine substituted hydrido ruthenium complexes
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Hydrido ruthenium carbonyl complexes substituted by functionalized phosphines such as H4Ru4(CO)8[P(CH2OCOR) 3]4 have been synthesized and tested as catalysts in the hydrogenation of carboxylic acids. These complexes are more active than those reported previously, containing trialkyl- or triarylphosphines. On the basis of their behavior, their different activity has been explained in terms of an involvement of the phosphine ligand in the catalytic cycle. The ester group present in the phosphine P(CH2OCOR)3 is hydrogenated to produce an alcohol (RCH2OH) and a P(CH2OH) group which, in turn, reacts with the free acid present in solution to restore the P(CH2OCOR) group. This hypothesis has been confirmed by the reactivity of the possible intermediate H4Ru4(CO)8[P(CH2OH) 3]4 with acetic acid. Another support to this statement is the almost equal catalytic activity, displayed by H4Ru4(CO)8[P(CH2OCOR) 3]4 complexes, whatever the R group present, in the phosphine ligand, in the hydrogenation of carboxylic acids. These complexes, on the other hand, are less active than the corresponding tributylphosphine substituted ones in the hydrogenation of alkenes and ketones. Finally when the phosphine ligand is P(CH2CH2COOCH3)3 the ester group is not reduced and consequently the catalytic activity of this complex in the hydrogenation of carboxylic acids is very low.
- Salvini, Antonella,Frediani, Piero,Bianchi, Mario,Piacenti, Franco,Pistolesi, Leonardo,Rosi, Luca
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p. 218 - 228
(2007/10/03)
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- RUTHENIUM CATALYZED TRANSFORMATION OF ALCOHOLS TO ESTERS AND LACTONES
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Homogeneous catalytic oxidative condensation of alcohols and diols to their corresponding esters and lactones has been accomplished using RuH2(PPh3)4.
- Murahashi, Shun-Ichi,Ito, Kei-ichiro,Naota, Takeshi,Maeda, Yoshihiro
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p. 5327 - 5330
(2007/10/02)
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