cas 75-89-8, 2,2,2-Trifluoroethanol | Articles data

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An adhesive 19F MRI chemical probe allows signal off-to-on-type molecular sensing in a biological environment
We report a new strategy for designing a signal off-to-on-type 19F MRI chemical probe that operates in biological environments. The present strategy is based on the control of adherence of a 19F MRI chemical probe to certain blood proteins, accompanied by a change in transverse relaxation time of 19F nuclei.
Doura, Tomohiro,Hata, Ryunosuke,Nonaka, Hiroshi,Sugihara, Fuminori,Yoshioka, Yoshichika,Sando, Shinsuke
p. 11421 - 11423
(2013)
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Method for recovering trifluoroethanol in multi-component solvent
The invention discloses a method for recovering trifluoroethanol in a multi-component solvent, which comprises the following steps of: by taking kettle residues obtained by recovering a solvent evaporated from an organic layer in the synthesis process of an efavirenz intermediate (S)-5-chloro-alpha-(cyclopropyl ethyl)-2-amino-alpha-(trifluoromethyl) benzyl alcohol as a raw material, forming sodium trifluoroethoxide from the raw material and caustic soda flakes, evaporating to remove excessive solvent, adding water for dissolving, adjusting the pH value, extracting and rectifying to obtain trifluoroethanol. The method for recovering trifluoroethanol in a multi-component solvent is simple in process, turns wastes into wealth, favorably improves the recovery rate of trifluoroethanol and increases the income, and is suitable for industrial production.
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Paragraph 0028; 0031-0032

(2022/01/12)

METHOD FOR OXIDATIVE CLEAVAGE OF COMPOUNDS WITH UNSATURATED DOUBLE BOND
A method for oxidative cleavage of a compound with an unsaturated double bond is provided. The method comprises the following step: (A) providing a compound (I) with an unsaturated double bond, a reagent with trifluoromethyl, and a catalyst; wherein the catalyst is represented by the following formula (II): M(O)mL1yL2z (II); wherein, M, L1, L2, m, y, z, R1, R2 and R3 are defined in the specification; and (B) mixing the compound with an unsaturated double bond and the reagent with a trifluoromethyl to perform an oxidation of the compound with the unsaturated double bond by using the catalyst at air or an oxygen condition to get a compound presented as formula (III):
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Paragraph 0053-0059

(2021/03/19)

Method for oxidative cracking of compound containing unsaturated double bonds
The invention relates to a method for oxidative cracking of a compound containing unsaturated double bonds. The method comprises the following steps: (A) providing a compound (I) containing unsaturated double bonds, a trifluoromethyl-containing reagent and a catalyst, wherein the catalyst is shown as a formula (II): M(O)mL1yL2z (II), M, L1, L2, m, y, z, R1, R2 and R3 being defined in the specification; and (B) mixing the compound containing the unsaturated double bonds and the trifluoromethyl-containing reagent, and performing an oxidative cracking reaction on the compound containing the unsaturated double bonds in the presence of air or oxygen by using the catalyst to obtain a compound represented by formula (III),.
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Paragraph 0108-0114; 0134-0136

(2021/07/09)

Transition Metal-Free Direct Hydrogenation of Esters via a Frustrated Lewis Pair
"Frustrated Lewis pairs"(FLPs) continue to exhibit unique reactivity for the reduction of organic substrates, yet to date, the catalytic hydrogenation of an ester functionality has not been demonstrated. Here, we report that iPr3SnNTf2 (1-NTf2; Tf = SO2CF3) is a more potent Lewis acid than the previously studied iPr3SnOTf; in an FLP with 2,4,6-collidine/2,6-lutidine (col/lut), this translates to faster H2 activation and the catalytic hydrogenolysis of an ester bond by a main-group compound, furnishing alcohol and ether (minor) products. The reaction outcome is sensitive to the steric and electronic properties of the substrate; CF3CO2Et and simple formates (HCO2Me and HCO2Et) are catalytically reduced, whereas related esters CF3CO2nBu and CH3CO2Et show only stoichiometric reactivity. A computational case study on the hydrogenation of CF3CO2Et and CH3CO2Et reveals that both share a common mechanistic pathway; however, key differences in the energies of a Sn-acetal intermediate and transition states emerge, favoring CF3CO2Et reduction. The alcohol products reversibly inhibit 1-NTf2/lut via formation of resting-state species 1-OR/[1·(1-OR)]+[NTf2]- however, the extra energy required to regenerate 1-NTf2/lut exacerbates the unfavorable reduction energy profile for CH3CO2Et, ultimately preventing turnover. These findings will assist the design of future main-group catalysts for ester hydrogenation, with improved performance.
Sapsford, Joshua S.,Csókás, Dániel,Turnell-Ritson, Roland C.,Parkin, Liam A.,Crawford, Andrew D.,Pápai, Imre,Ashley, Andrew E.
p. 9143 - 9150
(2021/07/31)

METHOD FOR OXIDATIVE CLEAVAGE OF COMPOUNDS WITH UNSATURATED DOUBLE BOND
A method for oxidative cleavage of a compound with an unsaturated double bond is provided. The method includes the steps of: (A) providing a compound (I) with an unsaturated double bond, a trifluoromethyl-containing reagent, and a catalyst; wherein, the catalyst is represented by Formula (II): M(O)mL1yL2z??(II);wherein, M, L1, L2, m, y, z, R1, R2 and R3 are defined in the specification; and(B) mixing the compound with an unsaturated double bond and the trifluoromethyl-containing reagent to perform an oxidative cleavage of the compound with the unsaturated double bond by using the catalyst in air or under oxygen atmosphere condition to obtain a compound represented by Formula (III):
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Paragraph 0071

(2021/07/10)

SYNTHESIS OF FLUORO HEMIACETALS VIA TRANSITION METAL-CATALYZED FLUORO ESTER AND CARBOXAMIDE HYDROGENATION
This application is directed to use of transition metal-ligand complexes to hydrogenate fluorinated esters and carboxamides into fluorinated hemiacetals. Methods for synthesis of certain ligands are also provided.
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Paragraph 0245-0250; 0261

(2020/11/24)

Synthesis of Fluorinated Dialkyl Carbonates from Carbon Dioxide as a Carbonyl Source
Fluorinated dialkyl carbonates (DACs), which serve as environmentally benign phosgene substitutes, were produced successfully from carbon dioxide either directly or indirectly. Nucleophilic addition of 2,2,2-trifluoroethanol to carbon dioxide and subsequent reaction with 2,2,2-trifluoroethyltriflate (3 a) afforded bis(2,2,2-trifluoroethyl) carbonate (1) in up to 79 % yield. Additionally, carbonate 1 was obtained through the stoichiometric reaction of 3 a and cesium carbonate. Although bis(1,1,1,3,3,3-hexafluoro-2-propyl) carbonate (4) was difficult to obtain by either of the above two methods, it could be synthesized through the transesterification of carbonate 1.
Sugiyama, Masafumi,Akiyama, Midori,Nishiyama, Kohei,Okazoe, Takashi,Nozaki, Kyoko
p. 1775 - 1784
(2020/03/23)

Engineering Catalysts for Selective Ester Hydrogenation
The development of efficient catalysts and processes for synthesizing functionalized (olefinic and/or chiral) primary alcohols and fluoral hemiacetals is currently needed. These are valuable building blocks for pharmaceuticals, agrochemicals, perfumes, and so forth. From an economic standpoint, bench-stable Takasago Int. Corp.'s Ru-PNP, more commonly known as Ru-MACHO, and Gusev's Ru-SNS complexes are arguably the most appealing molecular catalysts to access primary alcohols from esters and H2 (Waser, M. et al. Org. Proc. Res. Dev. 2018, 22, 862). This work introduces economically competitive Ru-SNP(O)z complexes (z = 0, 1), which combine key structural elements of both of these catalysts. In particular, the incorporation of SNP heteroatoms into the ligand skeleton was found to be crucial for the design of a more product-selective catalyst in the synthesis of fluoral hemiacetals under kinetically controlled conditions. Based on experimental observations and computational analysis, this paper further extends the current state-of-the-art understanding of the accelerative role of KO-t-C4H9 in ester hydrogenation. It attempts to explain why a maximum turnover is seen to occur starting at 25 mol % base, in contrast to only 10 mol % with ketones as substrates.
Dub, Pavel A.,Batrice, Rami J.,Gordon, John C.,Scott, Brian L.,Minko, Yury,Schmidt, Jurgen G.,Williams, Robert F.
p. 415 - 442
(2020/03/04)

Optimization and sustainability assessment of a continuous flow Ru-catalyzed ester hydrogenation for an important precursor of a β2-adrenergic receptor agonist
The development of a ruthenium-catalyzed continuous flow ester hydrogenation using hydrogen (H2) gas is reported. The reaction was utilized for the reduction of an important precursor in the synthesis of abediterol, a β2-adrenoceptor agonist that has undergone phase IIa clinical trials for the treatment of asthma and chronic obstructive pulmonary disorder. The reaction was investigated within a batch autoclave by using a design of experiments (DoE) approach to identify important parameter effects. The optimized flow process was successfully operated over 6 h with inline benchtop19F NMR spectroscopy for reaction monitoring. The protocol is shown to be high yielding (98% yield, 3.7 g h?1) with very low catalyst loading (0.065 mol%). The environmental impact of the Ru-catalyzed hydrogenation was assessed and compared to an existing stoichiometric lithium aluminum hydride (LAH) reduction and sodium borohydride (NaBH4) reduction. The process mass intensity (PMI) for the Ru-catalyzed hydrogenation (14) compared favorably to a LAH reduction (52) and NaBH4reduction (133).
García-Lacuna, Jorge,Hone, Christopher A.,Kappe, C. Oliver,Leslie, Kevin,Munday, Rachel,O'Kearney-McMullan, Anne,Prieschl, Michael
supporting information
p. 5762 - 5770
(2020/09/21)

Synthesis of β-hydroxyamides through ruthenium-catalyzed hydration/transfer hydrogenation of β-ketonitriles in water: Scope and limitations
A cascade process for the straightforward one-pot conversion of β-ketonitriles into β-hydroxyamides is presented. The process, that proceeds in water employing the arene-ruthenium(II) complex [RuCl2(η6-p-cymene){P(4-C6H4F)2Cl}] as catalyst in combination with sodium formate, involves the initial hydration of the β-ketonitrile substrates to generate the corresponding β-ketoamide intermediates, which subsequently undergo the transfer hydrogenation (TH) of the carbonyl group. Employing a family of forty different β-ketonitriles, featuring diverse substitution patterns, the scope and limitations of the process have been established.
González-Fernández, Rebeca,Crochet, Pascale,Cadierno, Victorio
p. 90 - 101
(2019/06/18)

Ru-Catalyzed Transfer Hydrogenation of Nitriles, Aromatics, Olefins, Alkynes and Esters
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.
p. 4860 - 4869
(2018/10/02)

RUTHENIUM COMPLEXES AND THEIR USES AS CATALYSTS IN PROCESSES FOR FORMATION AND/OR HYDROGENATION OF ESTERS, AMIDES AND RELATED REACTIONS
The present invention relates to novel Ruthenium complexes of formulae A1-A4 and their use, inter alia, for (1) dehydrogenative coupling of alcohols to esters; (2) hydrogenation of esters to alcohols (including hydrogenation of cyclic esters (lactones) or cyclic di-esters (di-lactones), or polyesters); (3) preparing amides from alcohols and amines—(including the preparation of polyamides (e.g., polypeptides) by reacting dialcohols and diamines and/or polymerization of amino alcohols and/or forming cyclic dipeptides from p-aminoalcohols; (4) hydrogenation of amides (including cyclic dipeptides, polypeptides and polyamides) to alcohols and amines; (5) hydrogenation of organic carbonates (including polycarbonates) to alcohols or hydrogenation of carbamates (including polycarbamates) or urea derivatives to alcohols and amines; (6) dehydrogenation of secondary alcohols to ketones; (7) amidation of esters (i.e., synthesis of amides from esters and amines); (8) acylation of alcohols using esters; (9) coupling of alcohols with water and a base to form carboxylic acids; and (10) preparation of amino acids or their salts by coupling of amino alcohols with water and a base. The present, invention further relates to the use of certain known Ruthenium complexes for the preparation of amino acids or their salts from amino alcohols.
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Paragraph 0276; 0277

(2017/10/18)

Cooperative interplay between a flexible PNN-Ru(II) complex and a NaBH4 additive in the efficient catalytic hydrogenation of esters
A catalyst loading of between 0.001-0.05 mol% of the PNN-bearing ruthenium(II) complex [fac-PNN]RuH(PPh3)(CO) (PNN = 8-(2-diphenylphosphinoethyl)amidotrihydroquinoline), in combination with 5 mol% NaBH4, efficiently catalyzes the hydrogenation of esters to their corresponding alcohols under mild pressures of hydrogen. Both aromatic and aliphatic esters can be converted with high values of TON or TOF achievable. Mechanistic investigations using both DFT calculations and labeling experiments highlight the cooperative role of NaBH4 in the catalysis while the catalytically active species has been established as trans-dihydride [mer-PNHN]RuH2(CO) (PNHN = 8-(2-diphenylphosphinoethyl)aminotrihydroquinoline). The stereo-structure of the PNHN-ruthenium species greatly affects the activity of the catalyst, and indeed the cis-dihydride isomer [fac-PNHN]RuH2(CO) is unable to catalyze the hydrogenation of esters until ligand reorganization occurs to give the trans isomer.
Wang, Zheng,Chen, Xiangyang,Liu, Bo,Liu, Qing-Bin,Solan, Gregory A.,Yang, Xinzheng,Sun, Wen-Hua
p. 1297 - 1304
(2017/05/05)

Direct Catalytic Hydrogenation of Simple Amides: A Highly Efficient Approach from Amides to Amines and Alcohols
A highly chemoselective and reactive direct catalytic reduction of various amides to amines and alcohols was developed by using a tetradentate ruthenium complex. The catalytic system showed excellent activity (turnover numbers up to 19 600) and great functional group tolerance under mild reaction conditions, compared to several bidentate and tridentate ruthenium-catalyzed systems.
Shi, Liyang,Tan, Xuefeng,Long, Jiao,Xiong, Xiong,Yang, Song,Xue, Peng,Lv, Hui,Zhang, Xumu
supporting information
p. 546 - 548
(2017/01/18)

Manganese-Catalyzed Hydrogenation of Esters to Alcohols
Homogeneous catalytic hydrogenation of esters to alcohols is an industrially important, environmentally benign reaction. While precious metal-based catalysts for this reaction are now well known, only very few catalysts based on first-row metal complexes were reported. Here we present the hydrogenation of esters catalyzed by a complex of earth-abundant manganese. The reaction proceeds under mild conditions and insight into the mechanism is provided based on an NMR study and the synthesis of novel Mn complexes postulated as intermediates.
Espinosa-Jalapa, Noel Angel,Nerush, Alexander,Shimon, Linda J. W.,Leitus, Gregory,Avram, Liat,Ben-David, Yehoshoa,Milstein, David
supporting information
p. 5934 - 5938
(2017/05/08)

MANGANESE BASED COMPLEXES AND USES THEREOF FOR HOMOGENEOUS CATALYSIS
The present invention relates to novel manganese complexes and their use, inter alia, for homogeneous catalysis in (1) the preparation of imine by dehydrogenative coupling of an alcohol and amine; (2) C-C coupling in Michael addition reaction using nitriles as Michael donors; (3) dehydrogenative coupling of alcohols to give esters and hydrogen gas (4) hydrogenation of esters to form alcohols (including hydrogenation of cyclic esters (lactones) or cyclic di-esters (di- lactones), or polyesters); (5) hydrogenation of amides (including cyclic dipeptides, lactams, diamide, polypeptides and polyamides) to alcohols and amines (or diamine); (6) hydrogenation of organic carbonates (including polycarbonates) to alcohols or hydrogenation of carbamates (including polycarbamates) or urea derivatives to alcohols and amines; (7) dehydrogenation of secondary alcohols to ketones; (8) amidation of esters (i.e., synthesis of amides from esters and amines); (9) acylation of alcohols using esters; (10) coupling of alcohols with water and a base to form carboxylic acids; and (11) preparation of amino acids or their salts by coupling of amino alcohols with water and a base. (12) preparation of amides (including formamides, cyclic dipeptides, diamide, lactams, polypeptides and polyamides) by dehydrogenative coupling of alcohols and amines; (13) preparation of imides from diols.
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Paragraph 00352-00353

(2017/09/05)

Why does alkylation of the N-H functionality within M/NH bifunctional Noyori-type catalysts lead to turnover?
Molecular metal/NH bifunctional Noyori-type catalysts are remarkable in that they are among the most efficient artificial catalysts developed to date for the hydrogenation of carbonyl functionalities (loadings up to ～10-5 mol %). In addition, these catalysts typically exhibit high C=0/C=C chemo- and enantioselectivities. This unique set of properties is traditionally associated with the operation of an unconventional mechanism for homogeneous catalysts in which the chelating ligand plays a key role in facilitating the catalytic reaction and enabling the aforementioned selectivities by delivering/accepting a proton (H+) via its N-H bond cleavage/formation. A recently revised mechanism of the Noyori hydrogenation reaction (Dub, P. A et al. J. Am. Chem. Soc. 2014,136,3505) suggests that the N-H bond is not cleaved but serves to stabilize the turnover-determining transition states (TDTSs) via strong N-H···O hydrogen-bonding interactions (HBIs). The present paper shows that this is consistent with the largely ignored experimental fact that alkylation of the N-H functionality within M/NH bifunctional Noyori-type catalysts leads to detrimental catalytic activity. The purpose of this work is to demonstrate that decreasing the strength of this HBI, ultimately to the limit of its complete absence, are conditions under which the same alkylation may lead to beneficial catalytic activity.
Dub, Pavel A.,Scott, Brian L.,Gordon, John C.
supporting information
p. 1245 - 1260
(2017/05/16)

Mechanistic insights into catalytic carboxylic ester hydrogenation with cooperative Ru(II)-bis{1,2,3-triazolylidene}pyridine pincer complexes
Transmetallation of newly designed lutidine-based CNC or CNN ligands L, featuring flanking 1,2,3-triazolylidene (tzNHCs) moieties, from Ag(I) to Ru(II) provided access to well-defined cationic [RuII(CO)(H)(L)(PPh3)]+ complexes 2 and 5. Spectroscopic investigations confirm that, in both complexes, the tridentate ligand binds in a rare facial mode to the metal center. The complexes, that exhibit ligand-based reversible deprotonation/dearomatization reactivity, are active in catalytic ester hydrogenation in the presence of KOtBu (≥20 mol%) as an exogenous base. The beneficial effect of the base on catalytic activity relates to transesterification of substrates to the corresponding tert-butyl ester derivatives, which are hydrogenated considerably faster than methyl esters. The mechanistic findings in this work confirm that this transformation is very complex, with this transesterification, metal-ligand cooperative reactivity, base strength and possibly product inhibition all playing a role. Furthermore, relevant Ru(CNC)(hydride) species have been observed by NMR spectroscopy under near-catalytic conditions.
Sluijter, Soraya N.,Korstanje, Ties J.,van der Vlugt, Jarl Ivar,Elsevier, Cornelis J.
supporting information
p. 30 - 37
(2017/07/22)

Expanding the Catalytic Scope of (Cyclopentadienone)iron Complexes to the Hydrogenation of Activated Esters to Alcohols
Herein, we report the application of easy-to-make and bench-stable (cyclopentadienone)iron complexes (such as 1) as precatalysts for the hydrogenation of esters. After optimization of the reaction conditions (i.e., solvent, temperature, pressure), complex 1 was tested in the hydrogenation of a range of esters. With most of the activated trifluoroacetate esters, quantitative formation of 2,2,2-trifluoroethanol was obtained at low catalyst loadings. For nonactivated esters, no reaction was observed. Trifluoroacetic acid, a common impurity in hydrolytically labile trifluoroacetate esters, was shown to act as a poison for the catalyst. However, the simple addition of Et3N allowed the catalyst activity to be restored. Our study constitutes the first examples of ester hydrogenation with an Fe complex based on a non-pincer ligand.
Gajewski, Piotr,Gonzalez-de-Castro, Angela,Renom-Carrasco, Marc,Piarulli, Umberto,Gennari, Cesare,de Vries, Johannes G.,Lefort, Laurent,Pignataro, Luca
p. 3431 - 3435
(2016/11/29)

Method for preparing alcohol through catalytic hydrogenation reduction of carboxylate
The invention discloses a method for preparing alcohol through catalytic hydrogenation reduction of a carboxylate compound with 2-(diphenylphosphinoethyl)-(5,6,7,8-tetrahydroquinolyl)amine as a ruthenium complex catalyst of ligand. The catalyst has high-efficiency catalysis activity on alkyl benzoate, aromatic esters and fatty esters. The preparation method is simple and has good stability, the catalysis activity of the catalyst is high, and the dosage of the catalyst is 0.025-0.005% of the mole of a substrate. The method can be used for producing alcohols, and has the advantages of simplicity, small pollution to environment, high yield and low cost. Most of carboxylate can be hydrogenated and reduced to form alcohols by using a complex represented by formula (1) with sodium borohydride as an additive, and the conversion number TOC can reach 50000; and a cocaalyst sodium borohydride is used to substitute most of alcoholic alkalis used as a catalyst in especially used in aromatic esters with electron-withdrawing substituent, so the cost is reduced, operation is simple, and industrial production is easy.
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Paragraph 0043; 0053

(2016/12/07)

Unprecedented iron-catalyzed selective hydrogenation of activated amides to amines and alcohols
The first example of hydrogenation of amides homogeneously catalyzed by an earth-abundant metal complex is reported. The reaction is catalyzed by iron PNP pincer complexes. A wide range of secondary and tertiary N-substituted 2,2,2-trifluoroacetamides were hydrogenated to form amines and trifluoroethanol.
Garg, Jai Anand,Chakraborty, Subrata,Ben-David, Yehoshoa,Milstein, David
supporting information
p. 5285 - 5288
(2016/05/02)

Iron-Catalyzed Hydrogenation of Amides to Alcohols and Amines
This article describes the iron-catalyzed hydrogenation of unactivated amides. Under the optimal conditions, a PNP-ligated Fe catalyst affords 25-300 turnovers of products derived from C-N bond cleavage. This reaction displays a broad substrate scope, including a variety of 2° and 3° amide substrates. The reaction progress of N,N-dimethylformamide hydrogenation has been monitored in situ using Raman spectroscopy. This technique enables direct comparison of the relative activity of the Fe-PNP catalyst to that of its Ru analogue. Under otherwise identical conditions, the Fe and Ru catalysts exhibit rates within a factor of 2.
Rezayee, Nomaan M.,Samblanet, Danielle C.,Sanford, Melanie S.
p. 6377 - 6383
(2016/10/14)

Transfer Hydrogenation of Nitriles, Olefins, and N-Heterocycles Catalyzed by an N-Heterocyclic Carbene-Supported Half-Sandwich Complex of Ruthenium
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.
supporting information
p. 943 - 949
(2016/05/09)

Hydrogenation of carboxylic acids with a homogeneous cobalt catalyst
The reduction of esters and carboxylic acids to alcohols is a highly relevant conversion for the pharmaceutical and fine-chemical industries and for biomass conversion. It is commonly performed using stoichiometric reagents, and the catalytic hydrogenation of the acids previously required precious metals. Here we report the homogeneously catalyzed hydrogenation of carboxylic acids to alcohols using earth-abundant cobalt. This system, which pairs Co(BF4)2·6H2O with a tridentate phosphine ligand, can reduce a wide range of esters and carboxylic acids under relatively mild conditions (100°C, 80 bar H2) and reaches turnover numbers of up to 8000.
Korstanje, Ties J.,Van Der Vlugt, Jarl Ivar,Elsevier, Cornelis J.,De Bruin, Bas
p. 298 - 302
(2015/10/29)

Transfer hydrogenation of ketones, nitriles, and esters catalyzed by a half-sandwich complex of ruthenium
Half-sandwich complexes [Cp(PiPr3)Ru(CH3CN)2]PF6 (1; Cp = cyclopentadienyl) and [Cp(phen)Ru(CH3CN)]PF6 (2; Cp = pentamethylcyclopentadienyl, phen = phenanthroline) catalyse the transfer hydrogenation of ketones to alcohols, aldimines to amines, and nitriles to imines under mild conditions. In the latter process, the imine products come from the coupling of the amines formed initially with acetone derived from the reducing solvent (isopropanol). Among functionally substituted nitriles, the aldo and keto groups are reduced concomitantly with the cyano group, whereas ester and amido groups are tolerated. Amides and alkyl esters are not reduced under these conditions even upon heating to 70°C. However, phenylbenzoates and trifluoroacetates are reduced to alcohols. Kinetic studies on the reduction of acetophenone in isopropanol established that the reaction is first order in both the substrate and the alcohol. Stoichiometric mechanistic studies showed the formation of a hydride species. A hydride mechanism was proposed to account for these observations.
Lee, Sun-Hwa,Nikonov, Georgii I.
p. 107 - 113
(2015/01/30)

2,2,2-Trifluoroethylation of Styrenes with Concomitant Introduction of a Hydroxyl Group from Molecular Oxygen by Photoredox Catalysis Activated by Visible Light
The visible-light-induced photoredox difunctionalization reactions of styrenes with 1,1,1-trifluoro-2-iodoethane under an oxygen atmosphere in the presence of water give γ-trifluoromethyl alcohols. In this radical reaction, the oxygen atom in the product originates from molecular oxygen, and water is shown to be important to promote the reaction.
Li, Lun,Huang, Meiwei,Liu, Chao,Xiao, Ji-Chang,Chen, Qing-Yun,Guo, Yong,Zhao, Zhi-Gang
p. 4714 - 4717
(2015/10/12)

Air-Stable NNS (ENENES) Ligands and Their Well-Defined Ruthenium and Iridium Complexes for Molecular Catalysis
We introduce ENENES, a new family of air-stable and low-cost NNS ligands bearing NH functionalities of the general formula E(CH2)mNH(CH2)nSR, where E is selected from -NC4H8O, -NC4H8, or -N(CH3)2, m and n = 2 and/or 3, and R = Ph, Bn, Me, or SR (part of a thiophenyl fragment). The preparation and characterization of more than 15 examples of well-defined Ru and Ir complexes supported by these ligands that are relevant to bifunctional metal-ligand M/NH molecular catalysis are reported. Reactions of NNS ligands with suitable Ru or Ir precursors afford rich and diverse solid-state and solution chemistries, producing monometallic molecules as well as bimetallics in which the ligand coordinates to the metal via either bidentate (κ2[N,N'] or κ2[N',S]) or tridentate (κ3[N,N',S]) binding modes, depending on the basicity of the sulfur atom, CH2 chain length (m or n parameter), or identity of the transition metal. In the case of Ir, ligands bearing benzyl substituents lead to unprecedented κ4[N,N',S,C]-tetradentate core-structure complexes of the type [IrIIIHCl{κ4(N,N',S,C)-ligand}], resulting from ortho-metalation via C-H oxidative addition. Fourteen of these Ru and Ir complexes have been crystallographically characterized. Air- and moisture-stable complexes of the type trans-[RuIICl2{κ3[N,N',S]-ligand}(L)] (L = PPh3, PCy3, DMSO), and others, effect the selective hydrogenation of methyl trifluoroacetate into the important synthon trifluoroacetaldehyde methyl hemiacetal in basic methanol under relatively mild conditions (35-40 °C, 25 bar H2) with reasonable turnover numbers (i.e., > 1000), whereas the air-stable Ir monohydride complexes [IrIIIHCl{κ4(N,N',S,C)-ligand}] exhibit excellent catalytic activities and high chemoselectivity for the same reaction, reaching turnover numbers of >10 000.
Dub, Pavel A.,Scott, Brian L.,Gordon, John C.
supporting information
p. 4464 - 4479
(2015/10/06)

POLYDENTATE LIGANDS AND THEIR COMPLEXES FOR MOLECULAR CATALYSIS
The present invention relates generally to novel achiral and chiral sulfur-, nitrogen- and phosphorus-containing ligands, designated as NNS-type, P(0)NS-type, PNS-type, SNNS-type, SNNP(0)-type, or SNNP-type polydentate ligands and transition metal complexes of these ligands. The catalysts derived from these ligands and transition metal complexes may be used in a wide range of catalytic reactions, including hydrogenation and transfer hydrogenation of unsaturated organic compounds, dehydrogenation of alcohols and boranes, various dehydrogenative couplings, and other catalytic transformations.
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Page/Page column 111-114

(2016/01/01)

Unprecedented iron-catalyzed ester hydrogenation. Mild, selective, and efficient hydrogenation of trifluoroacetic esters to alcohols catalyzed by an iron pincer complex
The synthetically important, environmentally benign hydrogenation of esters to alcohols has been accomplished in recent years only with precious-metal-based catalysts. Here we present the first iron-catalyzed hydrogenation of esters to the corresponding alcohols, proceeding selectively and efficiently in the presence of an iron pincer catalyst under remarkably mild conditions. The replacement of precious-metal catalysts by an iron complex was accomplished for the synthetically important, environmentally benign hydrogenation of esters to alcohols under mild conditions. The iron pincer complex (see scheme) selectively and efficiently catalyzes the hydrogenation of trifluoroacetates under remarkably mild conditions (5-25 bar and 40 °C).
Zell, Thomas,Ben-David, Yehoshoa,Milstein, David
supporting information
p. 4685 - 4689
(2014/05/20)

PROCESS FOR PRODUCING A-FLUOROALDEHYDES
A production process of an α-fluoroaldehyde according to the present invention includes reaction of an α-fluoroester with hydrogen gas (H2) in the presence of a ruthenium complex. It is possible in the present invention to allow relatively easy industrial production of the α-fluoroaldehyde and to directly obtain, as stable synthetic equivalents of the α-fluoroaldehyde, not only a hydrate (as obtained by conventional techniques) but also a hemiacetal that is easy to purify and is of high value in synthetic applications. The present invention provides solutions to all problems in the conventional techniques and establishes the significantly useful process for production of the α-fluoroaldehyde.
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Paragraph 0059

(2014/06/24)

The ammonolysis of esters in liquid ammonia
The rates of ammonolysis of alkyl benzoate and phenylacetate esters in liquid ammonia increase with the acidity of the leaving group alcohol and show relatively large Bronsted βlg values of -1.18 and -1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Bronsted βlg obtained using the pKa of the leaving group alcohol in liquid ammonia is significantly reduced to ~ -0.7, which indicates that the rate-limiting step involves a reaction of the tetrahedral intermediate with little C-OR bond fission in the transition state. The solvolysis reaction is subject to significant catalysis by ammonium ion, which, surprisingly, generates a similar Bronsted βlg indicating little interaction between the ammonium ion and the leaving group. It is concluded that the rate-limiting step for the ammonium-ion-catalysed solvolysis of alkyl esters in liquid ammonia is the diffusion-controlled protonation of the zwitterionic tetrahedral intermediate T+- to give T+, which is rapidly deprotonated to give T0 which is compatible with the rate-limiting step for the uncatalysed reaction being the formation of the neutral T0 by a 'proton switch'. Copyright 2013 John Wiley & Sons, Ltd. The rates of ammonolysis of alkyl benzoate and phenylacetate esters in liquid ammonia increase with the acidity of the leaving group alcohol and show relatively large Bronsted βlg values of -1.18 and -1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Bronsted βlg obtained using the pKa of the leaving group alcohol in liquid ammonia is significantly reduced to ~ -0.7, which is compatible with the rate limiting step for the uncatalysed reaction being the formation of the neutral T0 by a 'proton switch'. Copyright
Griffin, Joseph,Atherton, John,Page, Michael I.
p. 1032 - 1037
(2014/01/06)

Ruthenium nanoparticles on colloidal carbon spheres: An efficient catalyst for hydrogenation of ethyl lactate in aqueous phase
A ruthenium catalyst supported on glucose-derived carbon spheres was prepared and characterized by TEM, XPS, FTIR TG-DTG and XRD. The Ru/CSP catalyst showed an excellent catalytic performance for the hydrogenation of ethyl lactate to 1, 2-propanediol in water. The catalyst was recycled for six times without the marked loss in both the activity and selectivity. The steric hindrance and electronic effects of substrates on the hydrogenation were tested. It is postulated that the high performance of this novel catalyst system is related to the cooperation between the hydroxyl groups of support surface and water as a solvent.
Yang, Qin,Zhang, Jie,Zhang, Lei,Fu, Haiyan,Zheng, Xueli,Yuan, Maolin,Chen, Hua,Li, Ruixiang
p. 37 - 41
(2013/07/26)

Practical selective hydrogenation of α-fluorinated esters with bifunctional pincer-type ruthenium(II) catalysts leading to fluorinated alcohols or fluoral hemiacetals
Selective hydrogenation of fluorinated esters with pincer-type bifunctional catalysts RuHCl(CO)(dpa) 1a, trans-RuH2(CO)(dpa) 1b, and trans-RuCl2(CO)(dpa) 1c under mild conditions proceeds rapidly to give the corresponding fluorinated alcohols or hemiacetals in good to excellent yields. Under the optimized conditions, the hydrogenation of chiral (R)-2-fluoropropionate proceeds smoothly to give the corresponding chiral alcohol without any serious decrease of the ee value.
Otsuka, Takashi,Ishii, Akihiro,Dub, Pavel A.,Ikariya, Takao
supporting information
p. 9600 - 9603
(2013/07/26)

P-Aminophenyl alkyl ether-based 19F MRI probe for specific detection and imaging of hypochlorite ion
We report a 19F MRI probe for the specific detection and imaging of -OCl. Our designed probe, having p-aminophenyl alkyl scaffold, reacted expeditiously with -OCl to produce a trifluoroethanol. Concomitant with the reaction, the 19F chemical shift changed by 2.6 ppm, allowing the visualization of -OCldependent probe-to-product conversion using 19F MRI.
Doura, Tomohiro,An, Qi,Sugihara, Fuminori,Matsuda, Tetsuya,Sando, Shinsuke
supporting information; experimental part
p. 1357 - 1359
(2012/01/12)

Hyperaromatic stabilization of arenium ions: Cyclohexa- and cycloheptadienyl cations-experimental and calculated stabilities and ring currents
Measurements of pKR show that the cycloheptadienyl cation is less stable than the cyclohexadienyl (benzenium) cation by 18 kcal mol -1. This difference is ascribed here to "hyperaromaticity" of the latter. For the cycloheptadienyl cation a value of KR = [ROH][H+]/[R+] is assigned by combining a rate constant for reaction of the cation with water based on the azide clock with a rate constant for the acid-catalyzed formation of the cation accompanying equilibration of cycloheptadienol with its trifluoroethyl ether in TFE-water mixtures. Comparison of pKR = -16.1 with pKR = -2.6 for the cyclohexadienyl cation yields the difference in stabilities of the two ions. Interpretation of this difference in terms of hyperconjugative aromaticity is supported by the effect of benzannelation in reducing pKR for the benzenium ion: from -2.6 down to -3.5 for the 1H-naphthalenium and -6.0 for the 9H-anthracenium ions, respectively. MP2/6-311+G* and G3MP2 calculations of hydride ion affinities of benzenium ions show an order of stabilities for substituents at the methylene group consistent with their hyperconjugative abilities, i.e., (H3Si)2 > cyclopropyl > H 2 > Me2> (HO)2 > F2. Calculations of ring currents show a similar ordering. No conventional ring current is seen for the cycloheptadienyl cation, whereas currents in the F 2-substituted benzenium ion are consistent with antiaromaticity. Arenium ions where the methylene group is substituted with a single OH group show characteristic energy differences between conformations, with C-H or C-OH bonds respectively occupying or constrained to axial positions favorable to hyperconjugation. The differences were found to be 8.8, 6.3, 2.4, and 0.4 kcal mol-1 for benzenium, naphthalenium, phenanthrenium, and cyclohexenyl cations, respectively.
Lawlor, David A.,Bean, David E.,Fowler, Patrick W.,Keeffe, James R.,Kudavalli, Jaya Satyanarayana,More O'Ferrall, Rory A.,Rao, S. Nagaraja
supporting information; experimental part
p. 19729 - 19742
(2012/01/31)

UV absorption cross sections between 230 and 350 nm and pressure dependence of the photolysis quantum yield at 308 nm of CF3CH2CHO
Ultraviolet (UV) absorption cross sections of CF3CH 2CHO were determined between 230 and 350 nm by gas-phase UV spectroscopy. The forbidden n → π* transition was characterized as a function of temperature (269-323 K). In addition, the photochemical degradation of CF3CH2CHO was investigated at 308 nm. The possible photolysis channels are: CF3CH2 + HCO (R1a), CF3CH3 + CO (R1b), and CF3CH2CO + H (R1c). Photolysis quantum yields of CF3CH2CHO at 308 nm, Φλ=308nm, were measured as a function of pressure (25-760 Torr of synthetic air). The pressure dependence of Φ λ=308nm can be expressed as the following Stern-Volmer equation: 1/Φλ=308nm = (4.65 ± 0.56) + (1.51 ± 0.04) × 10-18 [M] ([M] in molecule cm-3). Using the absorption cross sections and the photolysis quantum yields reported here, the photolysis rate coefficient of this fluorinated aldehyde throughout the troposphere was estimated. This calculation shows that tropospheric photolysis of CF3CH2CHO is competitive with the removal initiated by OH radicals at low altitudes, but it can be the major degradation route at higher altitudes. Photodegradation products (CO, HC(O)OH, CF 3CHO, CF3CH2OH, and F2CO) were identified and also quantified by Fourier transform infrared spectroscopy. CF3CH2C(O)OH was identified as an end-product as a result of the chemistry involving CF3CH2CO radicals formed in the OH + CF3CH2CHO reaction. In the presence of an OH-scavenger (cyclohexane), CF3CH2C(O)OH was not detected, indicating that channel (R1c) is negligible. Based on a proposed mechanism, our results provide strong evidences of the significant participation of the radical-forming channel (R1a).
Antinolo, Maria,Jimenez, Elena,Albaladejo, Jose
experimental part
p. 15936 - 15946
(2012/02/02)

Polyfluoroalkoxy phosphonic and phosphinic acid derivatives: II. Reversible esterase inhibitors
Polyfluoroalkyl esters of phosphoric, alkylphosphonic and 1-hydroxypolyfluoroalkylphosphonic acids exhibited significant antiesterase activity against various esterases of animal and microbial origin. Moreover, with some compounds reversible inhibition of enzymes was observed due to the specific influence of hydrophobic fragments of the target products.
Krutikova,Krutikov,Erkin
experimental part
p. 434 - 439
(2010/08/04)

Polyfluoroalloxy phosphonic and phosphinic acid derivatives: I. 1-Hydroxy-2,2,2-trichloroethylphosphinates
Polyfluoroalkyl esters of 1-hydroxy-2,2,2-trichloroethylphosphonic and aryl(alkyl-)phosphinic acids exhibited antienzyme activity towards esterases of animal and microbial origin. A good correlation is observed between high antiesterase activity of the target compounds and their physicochemical parameters, characterizing their structure.
Krutikova,Krutikov,Erkin
scheme or table
p. 428 - 433
(2010/08/04)

Hydrogen bonding between solutes in solvents octan-1-ol and water
The 1:1 equilibrium constants, K, for the association of hydrogen bond bases and hydrogen bond acids have been determined by using octan-1-ol solvent at 298 K for 30 acid-base combinations. The values of K are much smaller than those found for aprotic, rather nonpolar solvents. It is shown that the log K values can satisfactorily be correlated against αH 2?βH2, where αH 2 and βH2 are the 1:1 hydrogen bond acidities and basicities of solutes. The slope of the plot, 2.938, is much smaller than those for log K values in the nonpolar organic solvents previously studied. An analysis of literature data on 1:1 hydrogen bonding in water yields a negative slope for a plot of log K against αH 2?βH2, thus showing how the use of very strong hydrogen bond acids and bases does not lead to larger values of log K for 1:1 hydrogen bonding in water. It is suggested that for simple 1:1 association between monofunctional solutes in water, log K cannot be larger than about -0.1 log units. Descriptors have been obtained for the complex between 2,2,2-trifluoroethanol and propanone, and used to analyze solvent effects on the two reactants, the complex, and the complexation constant.
Abraham, Michael H.,Gola, Joelle M. R.,Cometto-Muniz, J. Enrique,Acree, William E.
experimental part
p. 7651 - 7658
(2011/02/25)

Trifluoroacetaldehyde: A useful industrial bulk material for the synthesis of trifluoromethylated amino compounds
The synthesis of various trifluoromethylated amino compounds was studied using trifluoroacetaldehyde, an industrial bulk material, as a starting compound. One general application of trifluoroacetaldehyde is the preparation of trifluoroethylamino derivatives via reductive amination reaction. This synthesis includes the formation of the corresponding N,O-acetal intermediates followed by their reduction using NaBH4 or 2-picoline borane complex, affording the target trifluoroethylamino compounds in moderate to good yields (47-87%). Another general application of trifluoroacetaldehyde is the synthesis of chiral α-substituted trifluoroethylamino compounds. In this synthesis, trifluoroacetaldehyde was first converted into the chiral trifluoromethyl tert-butyl sulfinimine, which was subjected to 1,2-nucleophilic addition reactions across its C{double bond, long}N double bond. The addition of phenyllithium afforded α-(phenyl)trifluoroethylamino derivative in 83% yield and with 96% de. Allylation and Reformatsky reactions produced the corresponding α-substituted trifluoroethylamino derivatives in 82 and 58% yields and with 90 and 91% de, respectively.
Mimura, Hideyuki,Kawada, Kosuke,Yamashita, Tetsuya,Sakamoto, Takeshi,Kikugawa, Yasuo
experimental part
p. 477 - 486
(2010/05/02)

The Ever-surprising chemistry of boron: Enhanced acidity of phosphine·boranes
The gas-phase acidity of a series of phosphines and their corresponding phosphine·borane derivatives was measured by FT-ICR techniques. BH 3 attachment leads to a substantial increase of the intrinsic acidity of the system (from 80 to 110 kJ mol-1). This acidity-enhancing effect of BH3 is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. This indicates that the enhancement of the acidity of protic acids by Lewis acids usually observed in solution also occurs in the gas phase. High- level DFT calculations reveal that this acidity enhancement is essentially due to stronger stabilization of the anion with respect to the neutral species on BH3 association, due to a stronger electron donor ability of P in the anion and better dispersion of the negative charge in the system when the BH3 group is present. Our study also shows that deprotonation of ClCH2PH2 and ClCH 2PH2·BH3 is followed by chloride departure. For the latter compound deprotonation at the BH3 group is found to be more favorable than PH2 deprotonation, and the subsequent loss of Cl- is kinetically favored with respect to loss of Cl - in a typical SN2 process. Hence, ClCH2PH 2·BH3 is the only phosphine·borane adduct included in this study which behaves as a boron acid rather than as a phosphorus acid.
Hurtado, Marcela,Yanez, Manuel,Herrero, Rebeca,Guerrero, Andres,Juan Z. Davalos,Jose-Luis, M. Abboud,Khater, Brahim,Guillemin, Jean-Claude
supporting information; experimental part
p. 4622 - 4629
(2009/12/29)

Spectrokinetic study of the reaction system of 2NO2?N 2O4 with some fluorinated derivatives of ethanol and propanols between 293-358 K in the gas phase
The gas phase kinetics of the reversible reactions between nitrogen tetroxide and some fluorinated alcohols in the reaction system 2NO 2?N2O4 (1, 2) N2O4 + ROH?RONO+ + HNO3 (3, 4) have been studied by UV-Vis spectrophotometry to follow the NO2 decay. The products - RONO (R = CH2FCH2, CHF2CH2, CF 3CH2, CHF2CF2CH2, CF 3CF2CH2, CF3CHCF3) - were identified by their UV spectra and the values of the maxima UV absorption cross sections were determined in the range 320-400 nm. The rate constants for the forward reaction are 10-19k3av/cm 3molec-1s-1 9.7±1.5; 2.5±0.4; 1.8±0.3; 23±3.5, 2.3±0.3, 0.2±0.03 and for the reverse reaction 10-19k4av/cm 3molec-1s-1 4.6±0.7; 5.5±0.8; 4.9±0.7; 9.1±1.4; 7.7±1.2; 23±3.5 at 298 K for the reaction with 2-fluoroethanol, 2,2-difluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, 2,2,3,3,3-pentafluoro-1-propanol and 1,1,1,3,3,3-hexafluoro-2-propanol, respectively, were derived by the computer simulation of monitored NO2 decay profiles. The temperature dependence of the bimolecular rate constants k3 and k4 were studied in the temperature range 293-358 K and the activation energy for the forward E3 and for the reverse E4 reaction were derived. From the observed temperature dependence of the equilibrium constants K3,4, expressed in terms of the van't Hoff equation, the thermochemical parameters for all reactions studied were estimated.
Wojcik-Pastuszka,Golonka,Ratajczak
p. 1559 - 1574
(2008/02/04)

Metal ion promoted transesterifications of carboxylate esters. A structure/activity study of the efficacy of Zn2+ and La3+ to catalyze the methanolysis of some aryl and aliphatic esters
The methanolysis of various aryl and aliphatic carboxylate esters promoted by methoxide, 1,5,9-triazacyclododecane: Zn2+(-OCH 3) and La3+(-OCH3), were studied and the derived rate constants (kOCH3, kcat 3:Zn(OCH3) and kcatLa(OCH3)) correlated in various ways. The metal ion catalyzed reactions are very much faster than the background reactions in some cases reaching up to 7 × 106-fold acceleration when present at concentrations of 5 mmol dm-3. The data for both metals exhibit non-linear Bronsted correlations with the pK a of the leaving group which are analyzed in terms of a change in rate limiting step from formation to breakdown of a metal-coordinated tetrahedral intermediate as the pKa increases above values of ～14.7. Plots of the log kOCH3 reaction vs. the log k cat, values for each metal ion indicate low sensitivity for aryl esters and a higher sensitivity for the aliphatic esters. A mechanistic rationale for the observations is presented.
Neverov, Alexei A.,Sunderland,Brown, R. Stan
p. 65 - 72
(2007/10/03)

PROCESS FOR PREPARATION OF 2,2,2-TRIFLUOROETHANOL
A method for producing 2,2,2-trifluoroethanol in which a γ-hydroxybutyric acid salt is reacted with 1,1,1-trifluoro-2-chloroethane to generate 2,2,2-trifluoroethanol is provided. This method leads to increased yields of 2,2,2-trifluoroethanol, facilitates the separation of salt byproducts and allows the recycling of an aprotic polar solvent. The present invention concerns a method for producing 2,2,2-trifluoroethanol in which a γ-hydroxybutyric acid salt is reacted with 1,1,1-trifluoro-2-chloroethane in an aprotic polar solvent to generate 2,2,2-trifluoroethanol. This method is characterized in that the γ-hydroxybutyric acid salt used contains no more than 6wt% of 4,4'-oxybis(butyric acid).
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(2008/06/13)

Predominant role of basicity of leaving group in α-effect for nucleophilic ester cleavage
It has been found that α-effects in nucleophilic reactions, unexpectedly large nucleophilicity due to adjacent unpaired electrons, are strongly dependent on the structure of substrate. The nucleophilic cleavages of 4-nitrobenzoate esters and 4-methylbenzo
Nomura, Yasuo,Kubozono, Takayasu,Hidaka, Makoto,Horibe, Mineko,Mizushima, Naoki,Yamamoto, Nobuyuki,Takahashi, Toshio,Komiyama, Makoto
p. 26 - 37
(2007/10/03)

Imidazolium salt assisted hydrolysis of 1-chloro-2,2,2-trifluoroethane
The use of imidazolium-based ionic liquids as promoters was found to be highly effective for the hydrolysis reaction of CF3CH2Cl with aqueous potassium acetate to produce 2,2,2-trifluoroethanol (TFE). Among ionic liquids tested, 1-butyl-3-methylimidazoliu
Lee, Hyunjoo,Kim, Kyung Hwan,Kim, Honggon,Lee, Sang Deuk,Kim, Hoon Sik
p. 95 - 98
(2007/10/03)

Racemization and hydrolysis of (S)-naproxen 2,2,2-trifluoroethyl ester in non-polar solvents by strong neutral bases: Implication for ion-pair kinetic basicity and hydrolysis
By using strong neutral bases as catalyst, a detailed investigation of the racemization of (S)-naproxen 2,2,2-trifluoroethyl ester was conducted in the non-polar solvents isooctane, cyclohexane and n-hexane. The second-order interconversion constant kint* as representing the ion-pair kinetic basicity in isooctane was first estimated and correlated with the equilibrium ion-pair basicity pKip in tetrahydrofuran, giving slopes of 0.768 and 0.689 for non-phosphazene and phosphazene bases, respectively, in the Bronsted correlations. The result was further compared with that for (S)-naproxen 2,2,2-trifluoroethyl thioester, showing about a 1-2 orders of magnitude enhancement of kint* for the corresponding thio-containing analogue. A smaller influence of non-polar solvents (i.e. isooctane, n-hexane and cyclohexane) on kint* was found. Kinetic analysis of the racemization and hydrolysis of (S)-naproxen 2,2,2-trifluoroethyl ester in isooctane and n-hexane containing 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and water suggests nucleophilic hydrolysis by the base, where the breakdown of tetrahedral intermediates I R1 and IS1 is the rate-limiting step and the hydrolysis constant khy is in proportion to the product of base and ion-pair concentrations. Copyright 2004 John Wiley & Sons, Ltd.
Lin, Man-Yuan,Lay, Eddy,Wen, Wen-Yen,Dewi, Hamza,Cheng, Yu-Chi,Tsai, Shau-Wei
p. 387 - 392
(2007/10/03)

Mild and convenient method for reduction of aliphatic and aromatic carboxylic acids and anhydrides with (pyridine)(tetrahydroborato)zinc complex as a new stable ligand-metal tetrahydroborate agent
Structurally different aliphatic and aromatic carboxylic acids and anhydrides are efficiently reduced to their corresponding alcohols with a new modified zinc tetrahydroborate agent, (pyridine)(tetrahydroborato)zinc complex, [(Py)Zn(BH4)2], in refluxing THF.
Zeynizadeh, Behzad,Zahmatkesh, Karam
p. 522 - 525
(2007/10/03)

Intramolecular general base catalyzed ester hydrolysis. The hydrolysis of 2-aminobenzoate esters
Rate constants have been obtained for the hydrolysis of the trifluoroethyl, phenyl, and p-nitrophenyl esters of 2-aminobenzoic acid at 50°C in H2O. The pseudo-first-order rate constants, kobsd, are pH independent from pH 8 to pH 4 (the pKa of the amine group conjugate acid). The 2-aminobenzoate esters hydrolyze with similar rate constants in the pH-independent reactions, and these water reactions are ～2-fold slower in D2O than in H2O. The most likely mechanism involves intramolecular general base catalysis by the neighboring amine group. The rate enhancements in the pH-independent reaction in comparison with the pH-independent hydrolysis of the corresponding para substituted esters or the benzoate esters are 50 - 100-fold. In comparison with the hydroxide ion catalyzed reaction, the enhancement in kobsd at pH 4 with the phenyl ester is 105-fold. Intramolecular general base catalyzed reactions are assessed in respect to their relative advantages and disadvantages in enzyme catalysis. A general base catalyzed reaction can be more rapid at low pH than a nucleophilic reaction that has a marked dependence on pH and the leaving group.
Fife, Thomas H.,Singh, Randhir,Bembi, Ramesh
p. 3179 - 3183
(2007/10/03)