- Rhodium Porphyrin Catalyzed Regioselective Transfer Hydrogenolysis of C-C σ-Bonds in Cyclopropanes with iPrOH
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A new rhodium porphyrin catalyzed regioselective transfer hydrogenolysis of both activated and unactivated cyclopropanes employing iPrOH as the hydrogen source was discovered. The reaction mechanism for the C-C σ-bond activation of cyclopropanes was identified through an initial radical substitution with rhodium(II) metalloporphyrin radical to give a rhodium porphyrin alkyl, followed by hydrogenolysis with iPrOH to give the corresponding acyclic alkanes and regenerate rhodium(II) metalloporphyrin radical.
- Chen, Chen,Feng, Shiyu,Chan, Kin Shing
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supporting information
p. 2582 - 2589
(2019/07/02)
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- Ru-Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
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This paper reports the preparation of new ruthenium(II) complexes supported by a pyrazole-phosphine ligand and their application to transfer hydrogenation of various substrates. These Ru complexes were found to be efficient catalysts for the reduction of nitriles and olefins. Heterocyclic compounds undergo transfer hydrogenation with good to moderate yields, affording examples of unusual hydrogenation of all-carbon-rings. Internal alkynes with bulky substituents show selective reduction to olefins with the unusual E–selectivity. Esters with strong electron-withdrawing groups can be reduced to the corresponding alcohols, if ethanol is used as the solvent. Possible mechanisms of hydrogenation and olefin isomerization are suggested on the basis of kinetic studies and labelling experiments.
- Alshakova, Iryna D.,Gabidullin, Bulat,Nikonov, Georgii I.
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p. 4860 - 4869
(2018/10/02)
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- Transfer Hydrogenation of Nitriles, Olefins, and N-Heterocycles Catalyzed by an N-Heterocyclic Carbene-Supported Half-Sandwich Complex of Ruthenium
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In the presence of KOBut, N-heterocyclic carbene-supported half-sandwich complex [Cp(IPr)Ru(pyr)2][PF6] (3) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) catalyzes transfer hydrogenation (TH) of nitriles, activated N-heterocycles, olefins, and conjugated olefins in isopropanol at the catalyst loading of 0.5%. The TH of nitriles leads to imines, produced as a result of coupling of the initially formed amines with acetone (produced from isopropanol), and showed good chemoselectivity. Reduction of N-heterocycles occurs for activated polycyclic substrates (e.g., quinoline) and takes place exclusively in the heterocycle. The TH also works well for linear and cyclic olefins but fails for trisubstituted substrates. However, the C = C bond of α,β-unsaturated esters, amides, and acids is easily reduced even for trisubstituted species, such as isovaleriates. Mechanistic studies suggest that the active species in these catalytic reactions is the trihydride Cp(IPr)RuH3 (5), which can catalyze these reactions in the absence of any base. Kinetic studies are consistent with a classical inner sphere hydride-based mechanism of TH.
- Mai, Van Hung,Nikonov, Georgii I.
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p. 943 - 949
(2016/05/09)
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- Ultrasound technology and molecular sieves improve the thermodynamically controlled esterification of butyric acid mediated by immobilized lipase from Rhizomucor miehei
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In this research, the effects of ultrasound stirring and the addition of molecular sieves on esterification reactions between butyric acid and several alcohols catalyzed by immobilized lipase from Rhizomucor miehei (Lipozyme RM-IM) were studied. Among the tested alcohols, 1-propanol and isobutanol allowed the highest activities, whereas Lipozyme RM-IM showed poor activities for esterification using secondary and tertiary alcohols. Different solvents were also tested and n-hexane was selected because of its reaction effects, besides being cheaper, available at low boiling point, and ease of recovery. Using the preselected alcohol and solvent, other reaction parameters (butyric acid concentration, temperature, substrate molar rate, and biocatalyst content) were studied to optimize the reaction conditions. Optimal conditions were acid concentration, 0.7 M; substrate molar ratio, 11 alcohol-acid; temperature 45 °C; biocatalyst content, 14% (by substrate mass). Under these conditions, it was possible to obtain a yield of 86% of butyl butyrate in 2.5 h. When molecular sieves (90 mg mmol-1 butytic acid) were added to the reaction, the observed yield increased to 96%. The biocatalyst was used in 5 successive reaction cycles keeping 100% of its initial activity. The overall process productivity was improved 2-fold when compared to the traditional mechanical agitation, showing that ultrasound is a promising technology for application in biocatalysis. The Royal Society of Chemistry.
- Fallavena, Lucas P.,Antunes, Fabio H. F.,Alves, Joana S.,Paludo, Natalia,Ayub, Marco A. Z.,Fernandez-Lafuente, Roberto,Rodrigues, Rafael C.
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p. 8675 - 8681
(2014/03/21)
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- Comparison of the performance of commercial immobilized lipases in the synthesis of different flavor esters
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In this work, it is compared the performance of three commercial lipase preparations (Novozym 435, Lipozyme TL-IM, and Lipozyme RM-IM) in the synthesis of flavor esters obtained by esterification of acetic, propionic, and butyric acids using ethanol, isopropyl alcohol, butanol, or pentanol. A comprehensive comparison was performed verifying activities of these three enzyme preparations versus the different couples of substrates, checking the obtained yields. In general, the longer the acid chain, the higher the reaction yields. Novozym 435 was the most efficient enzyme in most cases, and only Lipozyme RM-IM offered better results than Novozym 435 in the production of ethyl butyrate. Reactions with butyric acid showed the highest conversion rates using all biocatalysts. Using optimal substrates, the reactions catalyzed by the three enzymes were optimized using the response surface methodology, and the catalytic performance of the biocatalysts in repeated batches was assessed. After optimization, yields higher than 90% were obtained for all three enzymes, but Lipozyme TL-IM needed four-times more biocatalyst content than the other two preparations. Novozym 435 kept over 80% of its activity when reused in 9 successive batches, whereas Lipozyme RM-IM can be reused 5 times and Lipozyme TL-IM only 3 times. In general, Novozym 435 showed to be more suitable for these reactions than the other two enzyme preparations.
- Martins, Andrea B.,Da Silva, Alexandre M.,Schein, Mirela F.,Garcia-Galan, Cristina,Zachia Ayub, Marco A.,Fernandez-Lafuente, Roberto,Rodrigues, Rafael C.
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- SYNTHESIS OF HIGH CALORIC FUELS AND CHEMICALS
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In one embodiment, the present application discloses methods to selectively synthesize higher alcohols and hydrocarbons useful as fuels and industrial chemicals from syngas and biomass. Ketene and ketonization chemistry along with hydrogenation reactions are used to synthesize fuels and chemicals. In another embodiment, ketene used to form fuels and chemicals may be manufactured from acetic acid which in turn can be synthesized from synthesis gas which is produced from coal, biomass, natural gas, etc.
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Paragraph 0076
(2013/05/23)
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- Efficient and catalyst-free condensation of acid chlorides and alcohols using continuous flow
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An efficient, catalyst-free continuous flow procedure for the condensation of acid chlorides and alcohols was developed. Different esters could be obtained using this protocol with excellent conversions starting from the corresponding acid chlorides and alcohols in very short reaction times (5-7 min). The reaction was performed solventless for liquid reagents but requires a solvent for solid reagents in order to prevent clogging of the microreactor. Since no catalyst is needed, the purification of the reaction mixture is very straightforward. Scale-up of the reaction to a microreactor with an internal volume of 13.8 ml makes it possible to produce 2.2 g min-1 of ester with an isolated yield of 98% and recuperation of the formed HCl.
- Van Waes, Frederik E. A.,Cukalovic, A.,Stevens, Christian V.,Drabowicz, J.
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p. 2776 - 2779,4
(2020/09/14)
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- Rapeseed lipase catalyzed synthesis of butyl butyrate for flavour and nutraceutical applications in organic media
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Butyl butyrate, a short chain ester with fine fruity pineapple odour, is a significant flavour compound. Recent investigations show that butyrate esters also have anticancer activity. Factors influencing the synthesis of butyl butyrate by organic phase biocatalysis were investigated. Maximum ester yield of 89% was obtained when 0.25 M butanol and butyric acid were reacted at 25 °C for 48 h in the presence of 250 mg rape seed lipase acetone powder in hexane. Addition of water did not affect synthesis, while a water activity of 0.45 was found optimum. Of 15 different alcohols evaluated, isoamyl and (Z)-3- hexen-1-ol were esterified most effectively with molar conversion yields of 92.2 and 80.2%. Short chain primary alcohols such as methanol and medium-long chain alcohols, such as heptanol and octanol were esterified more slowly. The results show that rape seed lipase is versatile catalyst for ester synthesis with temperature stability range 5-50 °C.
- Liaquat, Muhammad
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experimental part
p. 6 - 13
(2012/06/18)
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- Novel desilylation of alpha-dimethylsilyl esters by electrochemically generated superoxide ion
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Electrochemical reduction of oxygen in the presence of an alpha-dimethylsilyl ester results in removal of the dimethylsilyl group. The reaction presumably proceeds by a mechanism involving electrochemically-generated superoxide ion.
- Kaimakliotis, Christos,Fry, Albert J.
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p. 5859 - 5861
(2007/10/03)
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- Structure-function correlation in lipase catalysed esterification reactions of short and medium carbon chain length alcohols and acids
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An attempt has been made to correlate the carbon chain lengths of acids and alcohols to the extent of esterification in the Rhizomucor miehei lipase catalyzed esterification reactions involving acids of carbon chain length C2-C5 and alcohols of carbon chain length C1-C8.
- Divakar, Soundar
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p. 1919 - 1922
(2007/10/03)
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- High pressure mechanistic diagnosis in Baeyer-Villiger oxidation of aliphatic ketones
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The pressure effect is examined in Baeyer-Villiger oxidation of aliphatic ketones. This effect is small, reflected in slightly negative activation volumes (-2 to -8 cm3 mol-1). These values allow the picturing of the volume profile. They refer to a late transition step and give support for a rate-determining migration step experiencing full concertedness.
- Jenner, Gérard
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p. 8969 - 8971
(2007/10/03)
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- Preparation of crystal form II of clarithromycin
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The present invention provides a process for the preparation of 6-O-methylerythromycin A Form II comprising converting erythromycin A to 6-O-methylerythromycin A and treating the 6-O-methylerythromycin A with a number of common organic solvents or mixtures of common organic solvents.
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- Preparation of salicylic acid resin supported FeCl3 lewis acid catalyst and its application in organic synthesis
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The catalytic effects of salicylic acid resin supported FeCl3 catalyst on the esterification of alcohol and carboxylic acid and on the acetalization (ketal formation) of aldehyde (ketone) and alcohol have been investigated.This catalyst is convenient to use, noncorrosive, easy to be separated from reactants and can be repeatedly used.
- Huirong, Yang,Yingde, Li Bina Cui
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p. 1233 - 1238
(2007/10/03)
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- Thermal Decomposition of Dialkoxyaluminum Carboxylates and Halocarboxylates
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Thermal decomposition of diisopropoxyaluminum carboxylates (i-PrO)2AlOCOR (R = Pr, i-Pr, CH2Cl, CH2Br, CH2I, and CCl3) and i-PrOAl(OCOR)(OCOR') (R, R' = Me, Pr, i-Pr, i-Bu, and t-Bu) was studied. Diisopropoxyaluminum carboxylates derived from unsubstituted acids decompose to form mainly esters, whose yields decrease with increasing branching in the acid moiety. Thermolysis of diisopropoxyaluminum halocarboxylates yields esters and acetone as the product of oxidation of the alkoxy group.
- Stepovik,Zaburdaeva,Razuvaeva
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p. 1204 - 1209
(2007/10/03)
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- A study on synthesis of esters by superacid resin catalysts
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Superacid resin as catalyst, instead of the strong acid cation exchange resin and sulfuric acid was used to synthesis n-butyl lactate. Some factors affection reaction, such as time, moles ratio of reactants and catalyst amount were studied. Results made known that time was shorten very much. Under our optimum conditions the ester yield was over 99.5%. In the other hand, superacid resin as catalyst was used to synthesis other esters, had result of raise ester yield and shorten the time of esterification.
- Yang,Li,Fang
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p. 3269 - 3275
(2007/10/02)
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- ANODIC OXIDATION OF BUTYRIC ACID - THE FORMATION OF DIALKYL CARBONATES IN THE REACTION OF POTASSIUM BUTYRATE AND POTASSIUM CARBONATE IN WATER (THE HOFER-MOEST REACTION)
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The electrolysis of potassium butyrate in water containing a large excess of potassium carbonate at a platinum anode gave, in very low yield, a mixture of ten liquid products consisting of some typical secondary products derived from propene which included 1-methylpentyl n-propyl carbonate and 2-methylpentyl n-propyl carbonate of which the latter was the major product of the electrolysis.
- Brettle, Roger,Khan, M. Akram
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p. 240 - 247
(2007/10/02)
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- ACTIVATION OF MIXED CARBOXILIC α-BROMOTOLUOYL ANHYDRIDES BY SILVER TETRAFLUOROBORATE. SYNTHESIS OF ESTERS AND THIOL ESTERS
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Mixed carboxylic α-bromotoluoyl anhydrides were activated by silver tetrafluoroborate through intramolecular cyclization and reacted with alcohols or thiols giving the corresponding esters or thiol esters in good yields with the elimination of phtalide.
- Fukuoka, Satoshi,Takimoto, Seiji,Katsuki, Tsutomu,Yamaguchi, Masaru
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p. 4711 - 4712
(2007/10/02)
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- ENZYMATIC REACTIONS IN ORGANIC SYNTHESIS: 2- ESTER INTERCHANGE OF VINYL ESTERS
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Ester interchange of vinyl esters appears to be a rapid and efficient way to obtain esters of primary and secondary alcohols, provided there is a hydrogen atom on the carbon adjacent to the carbonyl of the acyl moiety.
- Degueil-Castaing, M.,Jeso, B. De,Drouillard, S.,Maillard, B.
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p. 953 - 954
(2007/10/02)
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- Anodic Oxidation. Part 17. The Formation of Alkyl Methyl Carbonates in the Hofer-Moest Reaction in Methanol
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The liquid products from the electrolysis of sodium butanoate in methanol containing methyl sodium carbonate at a graphite anode include propyl and 1-methylethyl methyl carbonates. 1,1-Dimethylethyl methyl carbonate is amongst the liquid products from the electrolysis of sodium 2,2-dimethylpropanoate in methanol at a platinum anode in the presence or absence of methyl sodium carbonate.Typical secondary products derived from propene or 2-methylpropene are also present in the liquid products from each of these electrolyses.
- Brettle, Roger,Khan, M. Akhram,Rowbottom, John D.
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p. 2927 - 2929
(2007/10/02)
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- COMPETITIVE TYPE II ELIMINATIONS IN ALIPHATIC IMIDES
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Aliphatic imides have been shown to undergo type II eliminations across the imide moiety in addition to those on the C-alkyl chain and α cleavage reactions.
- Mazzocchi, Paul H.,Jameson, William,Nishiyama, Tomikiro,DeCamp, Ann
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p. 989 - 992
(2007/10/02)
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