- Stable carbocations XXIII. Generation and isolation of salts of ferrocenyl(alkoxy)methylium cations and their intermediacy in acid-promoted acetal hydrolysis
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Ferrocenyl(aloxy)methylium cations have been generated from (dialkoxymethyl)ferrocenes and isolated as tetrafluoroborate salts.Their structures and their reactivity towards nucleophiles have been investigated.
- Kenny, T. P. E.,Knipe, A. C.,Watts, W. E.
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Read Online
- A facial chemoenzymatic method for the preparation of chiral 1,2-dihydroxy-3,3,3,-trifluoropropanephosphonates
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A convenient and effective method for the preparation of chiral trifluoromethylated 1,2-dihydroxypropanephosphonates based on a chemoenzymatic approach was described. Ethyl trifluoromethylacetate was reacted with anion of methylphosphonate to give 2-oxo-3,3,3-trifluoropropanephosphonate and its hydrates, 2,2-dihydroxy-3,3,3-trifluoropropanephosphonates, which are reduced with sodium boronhydride affording 2-hydroxy-3,3,3-trifluoropropanephosphonates. The product thus obtained was then transferred to corresponding 1,2-vinyl-3,3,3-trifluoropropanephosphonate and followed by 1,2-dihydroxylation via potassium permanganate treatment. Enzymatic kinetic resolution of the resultant racemate by CALB or IM provided optically active 1,2-dihydroxy-3,3,3- trifluoropropanephosphonate with satisfactory chemical and enantiomeric yield.
- Yuan, Chengye,Li, Jinfeng,Zhang, Wenchi
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Read Online
- SN2 and E2 Branching of Main-Group-Metal Alkyl Intermediates in Alkane CH Oxidation: Mechanistic Investigation Using Isotopically Labeled Main-Group-Metal Alkyls
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The main-group-metal alkyl compounds trialkyltin and dialkylthallium have been utilized to investigate the mechanism of functionalization of monoalkyl thallium and lead species, proposed to be putative intermediates in alkane (RH) functionalization, formed via CH activation of alkanes (methane, ethane, and propane) using electrophilic Tl(III) and Pb(IV) in trifluoroacetic acid (HTFA). Two different organometallic transalkylation methods were used to generate the putative intermediates in situ. The results herein strongly support a mechanism of CH activation to generate a main-group-metal alkyl intermediate which undergoes reductive functionalization to generate the products, R-TFA, and the reduced metal salt. In the case of ethane there are two products, ethyl trifluoroacetate (EtTFA) and 1,2-bis(trifluoroacetoxy)ethylene glycol (EG(TFA)2), observed in the reaction mixture that are proposed to form in parallel from a common intermediate, EtTl(TFA)2. The alkyl transfer studies herein strongly support the simultaneous formation of both species from this intermediate. Furthermore, studies conducted using regiospecifically isotopically labeled diethylthallium salts strongly support an SN2 functionalization from EtTl(TFA)2 to give EtTFA (and reduced Tl(TFA)) and an E2 elimination (also from EtTl(TFA)2) to generate ethylene, which instantly reacts with an additional 1 equiv of Tl(TFA)3 to generate EG(TFA)2.
- Ess, Daniel H.,Gunsalus, Niles Jensen,Hashiguchi, Brian G.,Konnick, Michael M.,Koppaka, Anjaneyulu,Park, Sae Hume,Periana, Roy A.
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Read Online
- Electrocatalytic Oxyesterification of Hydrocarbons by Tetravalent Lead
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The selective catalytic oxidative monofunctionalization of gaseous alkanes found in natural gas and commodity chemicals such as benzene and cyclohexane is an important objective in the field of carbon-hydrogen bond activation. Past research has demonstrated the possibility of stoichiometric oxyesterification of such substrates using lead(IV) trifluoroacetate (PbIV(TFA)4) as oxidant, which is driven by the high 2-electron redox potential of lead(IV). However, this redox potential then precludes reoxidation of lead(II) by a convenient oxidant such as O2, nullifying an effective catalytic cycle. In order to utilize renewable energy resources as alternatives to high-temperature thermocatalysis, we demonstrate the room-temperature electrocatalytic oxyesterification of alkanes and benzene with PbIV(TFA)4 as catalysts. At 1.67 V versus SHE, alkanes and benzene yielded the corresponding trifluoroacetate esters at room temperature; typically, good yields and high faradaic efficiencies were observed. High intrinsic turnover frequencies were obtained, for example, of >1000 min-1 for the oxyesterification of ethane at 30 bar. An analysis of the possible mechanistic pathways based on previously investigated stochiometric reactions, cyclic voltammetry measurements, kinetic isotope effects, and model compounds led to the conclusion that catalysis involves lead-mediated proton-coupled electron transfer of alkanes at and to the anode, followed by reductive elimination through an SN2 reaction to yield the alkyl-TFA products. Similarly, lead-mediated electron transfer from benzene at and to the anode leads to phenyl-TFA. Cyclic voltammetry also shows the viability of in situ reoxidation of Pb(II) species. The synthesis results obtained as well as the mechanistic insight are important advances towards the realization of selective alkane and arene oxidation reactions.
- Haviv, Eynat,Herman, Adi,Khenkin, Alexander M.,Neumann, Ronny
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p. 10494 - 10501
(2021/08/31)
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- Low-Flammable Parahydrogen-Polarized MRI Contrast Agents
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Many MRI contrast agents formed with the parahydrogen-induced polarization (PHIP) technique exhibit biocompatible profiles. In the context of respiratory imaging with inhalable molecular contrast agents, the development of nonflammable contrast agents would nonetheless be highly beneficial for the biomedical translation of this sensitive, high-throughput and affordable hyperpolarization technique. To this end, we assess the hydrogenation kinetics, the polarization levels and the lifetimes of PHIP hyperpolarized products (acids, ethers and esters) at various degrees of fluorine substitution. The results highlight important trends as a function of molecular structure that are instrumental for the design of new, safe contrast agents for in vivo imaging applications of the PHIP technique, with an emphasis on the highly volatile group of ethers used as inhalable anesthetics.
- Ariyasingha, Nuwandi M.,Chekmenev, Eduard Y.,Chukanov, Nikita V.,Gelovani, Juri G.,Joalland, Baptiste,Koptyug, Igor V.,Kovtunov, Kirill V.,Nantogma, Shiraz,Salnikov, Oleg G.,Younes, Hassan R.
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p. 2774 - 2781
(2021/01/18)
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- Oxidation of fluoroalkyl alcohols using sodium hypochlorite pentahydrate [1]
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Fluoroalkyl alcohols are effectivity oxidized to the corresponding fluoroalkyl carbonyl compounds by reaction with sodium hypochlorite pentahydrate in acetonitrile in the presence of acid and nitroxyl radical catalysts. Although the reaction proceeded slower under a nitroxyl radical catalyst- free condition, the desired carbonyl compounds were obtained in high yields. For the reaction with fluoroalkyl allylic alcohols, the corresponding α,β-epoxyketone hydrates were obtained in high yields.
- Kirihara, Masayuki,Suzuki, Katsuya,Nakakura, Kana,Saito, Katsuya,Nakamura, Riho,Tujimoto, Kazuki,Sakamoto, Yugo,Kikkawa, You,Shimazu, Hideo,Kimura, Yoshikazu
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- Aerobic Partial Oxidation of Alkanes Using Photodriven Iron Catalysis
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Photodriven oxidations of alkanes in trifluoroacetic acid using commercial and synthesized Fe(III) sources as catalyst precursors and dioxygen (O2) as the terminal oxidant are reported. The reactions produce alkyl esters and occur at ambient temperature in the presence of air, and catalytic turnover is observed for the oxidation of methane in a pure O2 atmosphere. Under optimized conditions, approximately 17% conversion of methane to methyl trifluoroacetate at more than 50% selectivity is observed. It is demonstrated that methyl trifluoroacetate is stable under catalytic conditions, and thus overoxidized products are not formed through secondary oxidation of methyl trifluoroacetate.
- Cao, Yuan,Coutard, Nathan,Goldberg, Jonathan M.,Groves, John T.,Gunnoe, T. Brent,Jeffrey, Philip D.,Jia, Xiaofan,Valle, Henry U.
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supporting information
(2022/01/11)
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- Selective Photo-Oxygenation of Light Alkanes Using Iodine Oxides and Chloride
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Partial oxidation of light alkanes to generate alkyl esters has been achieved under photochemical conditions using mixtures of iodine oxides and chloride salts in trifluoroacetic acid (HTFA). The reactions are catalytic in chloride and are successful using compact fluorescent light, but higher yields are obtained using a mercury lamp. In this photo-initiated oxyesterification process, the robust alkyl ester products are resistant to over-oxidation, and under optimized conditions yields for alkyl ester production of ~50 % based on methane, ~60 % based on ethane (with a total functionalized yield of EtX (X=TFA or Cl) of 80 %) and ~30 % based on propane have been demonstrated. The reaction also proceeds in aqueous HTFA and dichloroacetic acid with lower yields. Mechanistic studies indicate that the process likely operates by a chlorine hydrogen atom abstraction pathway wherein alkyl radicals are generated, trapped by iodine, and converted to alkyl trifluoroacetates in situ.
- Liebov, Nichole S.,Goldberg, Jonathan M.,Boaz, Nicholas C.,Coutard, Nathan,Kalman, Steven E.,Zhuang, Thompson,Groves, John T.,Gunnoe, T. Brent
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p. 5045 - 5054
(2019/10/28)
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- DIRECT OXIDATIVE AMINATION OF HYDROCARBONS
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Provided is a process for converting a hydrocarbon comprising at least one C-H bond to a nitrogen-functionalized product. The process comprises contacting a hydrocarbon and (i) an oxidizing electrophile comprising (a) a main group element or transition metal in oxidized form and (b) at least one nitrogen-containing ligand, or (ii) an oxidant and a reduced form of an oxidizing electrophile comprising (a) a main group element or transition metal and (b) at least one nitrogen-containing ligand, in a solvent to provide the nitrogen-functionalized product and an electrophile reduction product. Further provided is an oxidizing composition comprising the oxidizing electrophile with at least one nitrogen-containing ligand and a non?oxidizable liquid.
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Paragraph 0156; 0166-0168
(2019/06/17)
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- Method for synthesizing ethyl trifluoroacetate
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The invention relates to a method for synthesizing ethyl trifluoroacetate. Raw materials in the method for synthesizing ethyl trifluoroacetate include trifluoroacetic acid and anhydrous ethanol, and acatalyst is a solid acid catalyst. The method provided by the invention is simple in process, low in equipment requirement, and thorough in reaction, with the purity of 99.5% or above, and the molaryield of 98.0% or above. The solid acid catalyst can be recycled after being dried, and the activity is not significantly decreased, so that the using amount of the catalyst is small. The overall costof the method provided by the invention is controlled to be relatively low, thus being suitable for industrial production.
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Paragraph 0022; 0023; 0024; 0025; 0026; 0027; 0028-0031
(2019/01/08)
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- Mechanism of Hydrocarbon Functionalization by an Iodate/Chloride System: The Role of Ester Protection
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Mixtures of chloride and iodate salts for light alkane oxidation achieve >20% yield of methyl trifluoroacetate (TFA) from methane with >85% selectivity. The mechanism of this C-H oxygenation has been probed by examining adamantane as a model substrate. These recent results lend support to the involvement of free radicals. Comparative studies between radical chlorination and iodate/chloride functionalization of adamantane afford statistically identical 3°:2° selectivities (~5.2:1) and kinetic isotope effects for C-H/C-D functionalization (kH/kD = 1.6(3), 1.52(3)). Alkane functionalization by iodate/chloride in HTFA is proposed to occur through H-atom abstraction by free radical species including Cl? to give alkyl radicals. Iodine, which forms by in situ reduction of iodate, traps alkyl radicals as alkyl iodides that are subsequently converted to alkyl esters in HTFA solvent. Importantly, the alkyl ester products (RTFA) are quite stable to further oxidation under the oxidizing conditions due to the protecting nature of the ester moiety.
- Schwartz, Nichole A.,Boaz, Nicholas C.,Kalman, Steven E.,Zhuang, Thompson,Goldberg, Jonathan M.,Fu, Ross,Nielsen, Robert J.,Goddard, William A.,Groves, John T.,Gunnoe, T. Brent
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p. 3138 - 3149
(2018/04/14)
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- Ethyl trifluoroacetate preparation method
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The invention discloses an ethyl trifluoroacetate preparation method which includes the steps: pre-adding an appropriate amount of trifluoroacetic acid, ethyl alcohol and concentrated sulfuric acid into a reaction kettle with a rectifying tower according to prescribed proportion, or directly adding a certain amount of ethyl trifluoroacetate; rising temperature, performing backflow, and adding the ethyl alcohol and the trifluoroacetic acid of predetermined proportion from the top ends of a tower kettle and an extraction section of the rectifying tower respectively after proportion of various components in the rectifying tower is balanced and stabilized; directly collecting products at the top end of the rectifying tower after the products are purified to obtain the ethyl trifluoroacetate. According to the preparation method, solid super-acid or concentrated sulfuric acid serves as a catalyst, the trifluoroacetic acid and the ethyl alcohol are continuously fed, water in the tower kettle is regularly and quantitatively removed, continuous generation is achieved, production capacity is improved, reaction yield can reach 99%, and product purity can reach 99.9%.
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Paragraph 0023-0025
(2017/06/06)
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- Ozone oxidation process of preparing a halogenated acetic acid and esters thereof (by machine translation)
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The invention belongs to the field of chemical synthesis, in particular to a halogenated acetic acid or a halogenated acetic acid ester compound preparation method; halogenated ethane (type I) by ozone oxidation after the reaction, the reaction with water or alcohol to obtain a halogenated acetic acid or halogenated acetate (type II). (by machine translation)
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Paragraph 0096-0098
(2017/06/29)
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- Synthesis of trifluoromethyl moieties by late-stage copper (I) mediated nucleophilic fluorination
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The nucleophilic fluorination of bromodifluoromethyl derivatives mediated by the complex (PPh3)3CuF is described. Under the reaction conditions, different trifluoroacetates, trifluoroketones, trifluoroarenes and trifluoroacetamides were obtained in good yields.
- Bermejo Góme, Antonio,González, Miguel A. Cortés,Lübcke, Marvin,Johansson, Magnus J.,Schou, Magnus,Szabó, Kálmán J.
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- A trifluoroacetic acid ethyl ester
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A synthesis method of ethyl trifluoroacetate comprises the steps: with trifluoroacetic acid and ethanol as raw materials, with strong acidic cation exchange resin as a catalyst, at a temperature of 40-50 DEG C and at normal pressure, dropwise adding ethanol and maintaining for 20 minutes, heating up and refluxing to separate out a water and ethanol mixture, and making the reaction completed; after collecting a crude product, continuing to use the kettle bottom catalyst and ethanol; adding water to the collected crude product to wash ethanol, stratifying to obtain ethyl trifluoroacetate with the yield of more than 95%; and refluxing to separate out dilute ethanol, and rectifying to obtain 95% ethanol for repeated use. The method omits a drying tower and a filtration device used in a conventional process; ethanol recovered from the reaction can be repeatedly used after treatment, the production cost is effectively reduced, and the method has the advantages of simple operation process, environmental protection, energy saving and no pollution; because price difference between trifluoroacetic acid and ethyl trifluoroacetate is not large, requirements on the product yield and cost are higher; and the method is complete and standardized in process, convenient to operate and suitable for industrialized production, and can effectively improve the purity and yield of the product.
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Paragraph 0037; 0038; 0039
(2016/12/26)
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- A process for the preparation of suitable ester
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The invention relates to a preparation method of trifluoroacetate. The preparation method is characterized by comprising the following steps: (1) after uniformly mixing potassium fluoride with alcohol, adding trifluoroacetyl fluoride for reaction; (2) filtering a reaction mixture to remove potassium fluoride-potassium bifluoride solids; and (3) rectifying to obtain the trifluoroacetate. The method provided by the invention simplifies the preparation process of the trifluoroacetate, no waste acids and catalysts are generated in the reaction process, and by-products of reaction can be recycled, so that the environmental protection problem in synthesis of the trifluoroacetate is solved.
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Paragraph 0023-0024
(2020/02/08)
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- A continuous non-catalytic method for preparation of trifluoro acetic acid ethyl ester
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The invention provides a process for preparing ethyl trifluoroacetate through a continuous non-catalytic method reaction of trifluoroacetyl chloride and ethanol under a reactive rectification condition. The process has the characteristics of conveniently and easily available raw materials, simple process, mild reaction conditions, low reaction energy consumption, and no waste liquid residue in the procedure, and is suitable for amplification production. The prepared ethyl trifluoroacetate can be used for synthesis of fluorine-containing pesticides, fluorine-containing medicines, fluorine-containing liquid crystals, fluorine-containing dyes and the like.
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Paragraph 0039; 0040
(2017/02/09)
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- A trifluoro acetyl ethyl acetate in the production process of the waste containing ethyl acetate and ethanol of resource utilization method
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The invention discloses a recycling method of waste containing ethyl acetate and ethyl alcohol in a production process of ethyl trifluoroacetoacetate. A mixture of ethyl trifluoroacetate and ethyl acetate is obtained by reaction of trifluoroacetyl chloride, ethyl acetate and ethyl alcohol under the operation condition of reactive rectification. The method disclosed by the invention has the advantages of low cost, safety, environmental friendliness, simple technology and the like.
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Paragraph 0028; 0029
(2017/06/02)
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- Partial oxidation of light alkanes by periodate and chloride salts
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The efficient and selective partial oxidation of light alkanes using potassium periodate and potassium chloride is reported. Yields of methane functionalization in trifluoroacetic acid reach >40% with high selectivity for methyl trifluoroacetate. Periodat
- Kalman, Steven E.,Munz, Dominik,Fortman, George C.,Boaz, Nicholas C.,Groves, John T.,Gunnoe, T. Brent
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supporting information
p. 5294 - 5298
(2015/03/30)
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- Selective CH Functionalization of Methane, Ethane, and Propane by a Perfluoroarene Iodine(III) Complex
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Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate esters is achieved by a homogeneous hypervalent iodine(III) complex in non-superacidic (trifluoroacetic acid) solvent. The reaction is highly selective for ester formation (>99 %). In the case of ethane, greater than 0.5 M EtTFA can be achieved. Preliminary kinetic analysis and density functional calculations support a nonradical electrophilic CH activation and iodine alkyl functionalization mechanism. Gas up: Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate (TFA) esters is achieved by a homogeneous hypervalent iodine(III) complex in non-superacidic solvent (HTFA). The reaction is highly selective, and for ethane, greater than 0.5 M Et=TFA can be achieved. Preliminary kinetic analysis and density functional calculations support a nonradical electrophilic CH activation and iodine alkyl functionalization mechanism.
- Konnick, Michael M.,Hashiguchi, Brian G.,Devarajan, Deepa,Boaz, Nicholas C.,Gunnoe, T. Brent,Groves, John T.,Gunsalus, Niles,Ess, Daniel H.,Periana, Roy A.
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supporting information
p. 10490 - 10494
(2016/02/18)
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- Beckmann rearrangement of acetophenone oximes to the corresponding amides organo-catalyzed by trifluoroacetic acid for sustainable NSAIDs synthesis
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The Beckmann rearrangement of acetophenone oximes to the corresponding amides (4-hydroxyacetophenone oxime to N-acetyl-4-hydroxyacetanilide and acetophenone oxime to N-phenylacetamide) is investigated by using trifluoroacetic acid (TFA) as catalyst. The reaction occurs either in the presence or in the absence of a suitable solvent. High selectivity and practically quantitative yield to amide is achieved in both cases at TFA/substrate > 3. Both TFA and the solvent (whenever present) could be easily reused by distillation since no protonation of amides occurs. The reaction proceeds via a multistep reaction path and the role of TFA is related not only to its acidity but also mainly to its ability on forming reactive trifluoroacetylated intermediates. In particular, the highly reactive trifluoroacetylated amide is actually the effective catalyst. Finally, a likely reaction path is proposed.
- Quartarone, Giuseppe,Rancan, Elia,Ronchin, Lucio,Vavasori, Andrea
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p. 167 - 177
(2014/02/14)
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- OXIDATION OF ALKANES TO ALCOHOLS
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The invention provides processes and materials for the efficient and cost- effective functionalization of alkanes, such as methane from natural gas, to provide esters, alcohols, and other compounds. The method can be used to produce liquid fuels such as methanol from a natural gas methane-containing feedstock. The soft oxidizing electrophile, a compound of a main group, post- transitional element such as Tl, Pb, Bi, and I, that reacts to activate the alkane C- H bond can be regenerated using inexpensive regenerants such as hydrogen peroxide, oxygen, halogens, nitric acid, etc. Main group compounds useful for carrying out this reaction includes haloacetate salts of metals having a pair of available oxidation states, such as Tl, Pb, Bi, and I. The inventors herein believe that a unifying feature of many of the MXn electrophiles useful in carrying out this reaction, such as Tl, Pb, and Bi species, is their isoelectronic configuration in the alkane -reactive oxidation state; the electrons having the configuation [Xe]4f145d10, with an empty 6s orbital. However, the iodine reagents have a different electronic configuration.
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Page/Page column 12; 13; 14
(2014/09/03)
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- Selective monooxidation of light alkanes using chloride and iodate
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We describe an efficient system for the direct partial oxidation of methane, ethane, and propane using iodate salts with catalytic amounts of chloride in protic solvents. In HTFA (TFA = trifluoroacetate), >20% methane conversion with >85% selectivity for MeTFA have been achieved. The addition of substoichiometric amounts of chloride is essential, and for methane the conversion increases from 20%. The reaction also proceeds in aqueous HTFA as well as acetic acid to afford methyl acetate. 13C labeling experiments showed that less than 2% of methane is overoxidized to 13CO2 at 15% conversion of 13CH4. The system is selective for higher alkanes: 30% ethane conversion with 98% selectivity for EtTFA and 19% propane conversion that is selective for mixtures of the mono- and difunctionalized TFA esters. Studies of methane conversion using a series of iodine-based reagents [I2, ICl, ICl3, I(TFA)3, I2O4, I 2O5, (IO2)2S2O 7, (IO)2SO4] indicated that the chloride enhancement is not limited to iodate.
- Fortman, George C.,Boaz, Nicholas C.,Munz, Dominik,Konnick, Michael M.,Periana, Roy A.,Groves, John T.,Brent Gunnoe
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p. 8393 - 8401
(2014/06/24)
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- Main-group compounds selectively oxidize mixtures of methane, ethane, and propane to alcohol esters
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Much of the recent research on homogeneous alkane oxidation has focused on the use of transition metal catalysts. Here, we report that the electrophilic main-group cations thallium(III) and lead(IV) stoichiometrically oxidize methane, ethane, and propane, separately or as a one-pot mixture, to corresponding alcohol esters in trifluoroacetic acid solvent. Esters of methanol, ethanol, ethylene glycol, isopropanol, and propylene glycol are obtained with greater than 95% selectivity in concentrations up to 1.48 molar within 3 hours at 180°C. Experiment and theory support a mechanism involving electrophilic carbon-hydrogen bond activation to generate metal alkyl intermediates. We posit that the comparatively high reactivity of these d 10 main-group cations relative to transition metals stems from facile alkane coordination at vacant sites, enabled by the overall lability of the ligand sphere and the absence of ligand field stabilization energies in systems with filled d-orbitals.
- Hashiguchi, Brian G.,Konnick, Michael M.,Bischof, Steven M.,Gustafson, Samantha J.,Devarajan, Deepa,Gunsalus, Niles,Ess, Daniel H.,Periana, Roy A.
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p. 1232 - 1237
(2014/04/03)
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- SNAAP sulfonimidate alkylating agent for acids, alcohols, and phenols 1
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Stable, crystalline ethyl N-tert-butyl-4-nitrobenzenesulfonimidate has been prepared in high yield by direct O-ethylation of N-tert-butyl-4- nitrobenzenesulfonamide with iodoethane and silver(I) oxide in dichloromethane. This sulfonimidate directly ethylates various acids to esters; the stronger the acid, the faster it alkylates and in higher yield. It readily ethylates alcohols and phenols to ethers at room temperature in the presence of tetrafluoroboric acid catalyst without molecular rearrangements or racemization. We have defined these reactions as SNAAP alkylations: [substitution, nucleophilic of acids, alcohols and phenols]. The hard sulfonimidate alkylating agent is chemoselective, preferring oxygen > nitrogen > sulfur. The sulfonamide byproduct of alkylation is readily recycled to the sulfonimidate. Georg Thieme Verlag Stuttgart . New York.
- Maricich, Tom J.,Allan, Matthew J.,Kislin, Brett S.,Chen, Andrea I-T.,Meng, Fan-Chun,Bradford, Christine,Kuan, Nai-Chia,Wood, Jeremy,Aisagbonhi, Omonigho,Poste, Alethea,Wride, Dustin,Kim, Sylvia,Santos, Therese,Fimbres, Michael,Choi, Dianne,Elia, Haydi,Kaladjian, Joseph,Abou-Zahr, Ali,Mejia, Arturo
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p. 3361 - 3368
(2014/01/06)
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- METHOD FOR PREPARING DIFLUOROACETIC ACID
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A method for preparing difluoroacetic acid is described. The method can include: reacting a difluoroacetic acid ester with an aliphatic carboxylic acid which, after transesterification, results in the formation of difluoroacetic acid and the corresponding carboxylic acid ester, the carboxylic acid being selected such that the ester of the carboxylic acid has a lower boiling point than that of difluoroacetic acid; and removing the ester of the carboxylic acid by distillation as the ester forms, thus enabling the difluoroacetic acid to be recovered.
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Page/Page column 4
(2012/05/21)
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- Mechanistic pathways in CF3COOH-mediated deacetalization reactions
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(Chemical Equation Presented) It has been widely accepted that both the protection of carbonyls and the deprotection of acetals and ketals involve the participation of a water molecule: formation of acetals and ketals is a dehydration process, whereas the deprotection is often referred to as hydrolysis, which, as implied by its name, always requires the presence of water. Herein, we report experimental evidence and mechanistic investigations that provide an alternative view to this process. We have demonstrated that water is not required to convert acetals and ketals to the corresponding carbonyls. The 1H NMR experimental results revealed that the TFA-mediated transformation of acetal to aldehyde occurs via a hemiacetal TFA ester intermediate, which differentiates itself from the classic acid-catalyzed hydrolysis, where the hemiacetal is the putative intermediate responsible for the formation of the aldehyde. More interestingly, alcohols are not the final byproducts as they are in the classical hydrolysis, rather, the two alcohol molecules are converted to two TFA esters under the reaction conditions. On the basis of theNMRevidence, we have proposed that the two TFA esters are formed in two separate steps via a different mechanism along the reaction pathway. Formation of the TFA esters renders the reaction irreversible. To the best of our knowledge, the cascade reaction pathway presented by the TFA-mediated conversion of acetals and ketals to carbonyls has never been previously postulated.
- Li, Wei,Li, Jianchang,Wu, Yuchuan,Fuller, Nathan,Markus, Michelle A.
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experimental part
p. 1077 - 1086
(2010/04/04)
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- Catalytic oxidation of hydrocarbons of natural and oil gas
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Alkane oxidation by O2 and CO in the presence of Rh-, Pd-, and Pt-containing catalytic systems leads to the product of C-H bond oxidation and the products of C-C bond oxidative destruction. A deuterated methyl group in acetic acid is observed in the oxidation of n-propane in a deuterium-donor medium. The possible mechanisms of alkane C2-C4 conversion are proposed.
- Chepaikin,Bezruchenko,Menchikova,Moiseeva,Gekhman
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experimental part
p. 332 - 337
(2011/04/26)
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- Homogeneous catalytic oxidation of light alkanes: C-C bond cleavage under mild conditions
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The combined oxidation of CO and C2-C4 alkanes (associated petroleum gas and natural gas components) under the action of oxygen in trifluoroacetic acid solutions in the presence of rhodium and copper chlorides was accompanied by the oxidative degradation of C-C bonds in a hydrocarbon chain with the formation of carbonyl compounds, alcohols, and esters. For butane and isobutane, the reaction path with C-C bond cleavage was predominant. The buildup curves of isobutane oxidation products (both with the retention and with the degradation of the chain) were S-shaped and characterized by the same induction period; they did not pass through a maximum. A reaction scheme was proposed to reflect the main special features of the mechanism of transformations occurring in the O2/Rh/Cu/Cl- oxidation system.
- Chepaikin,Bezruchenko,Menchikova,Moiseeva,Gekhman
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experimental part
p. 666 - 671
(2011/02/16)
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- Facile synthesis of α,α-difluoroalkyl aryl thioethers and their oxidative desulfurization-fluorination to trifluorides
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Alkyl 2-arylthio-2,2-difluoroacetates are synthesized in 52-77% yield from alkyl 2-(arylthio)acetates via two succeeding fluoro-Pummerer rearrangements using the reagents combination of N-haloimides as electrophiles and excess Py·9HF as the fluoride source at room temperature. Subsequent treatment of the formed fluorinated thioethers with the same reagents at elevated temperature gave alkyl trifluoroacetates in almost quantitative yield under optimised conditions by oxidative desulfurization-fluorination.
- Hugenberg, Verena,Haufe, Günter
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experimental part
p. 942 - 950
(2010/10/02)
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- 1-(a-Aminobenzyl)-2-naphthol: A new chiral auxiliary for the synthesis of enantiopure a-aminophosphonic acids
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A new diastereoselective synthesis of a-aminophosphonates has been developed, based on the reaction, in the presence of trifluoroacetic acid, of trialkyl phosphites with chiral imines derived from (R)- or (S)-l-(ot- aminobenzyl)-2-naphthol. The reaction p
- Metlushka, Kirill E.,Kashemirov, Boris A.,Zheltukhin, Viktor F.,Sadkova, Dilyara N.,Buechner, Bernd,Hess, Christian,Kataeva, Olga N.,McKenna, Charles E.,Alfonsov, Vladimir A.
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experimental part
p. 6718 - 6722
(2010/02/28)
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- Heterolytic decarboxylation involving acyltrifluoroacetyl peroxide intermediates
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Selective carboxylic acid decarboxylation was elaborated. Generation of acyltrifluoroacetyl peroxides from carboxylic peracids and trifluoroacetyl anhydride (Method A), as well as from trifluoroperacetic acid and acyltrifluoroacetyl anhydride (Method B), leads to simultaneous peroxide decomposition into the corresponding alkyltrifluoroacetates. DFT computations, as well as experimental data, support an acid-catalyzed heterolytic mechanism for acyltrifluoroacetyl peroxide decomposition.
- Krasutsky, Pavel A.,Kolomitsyn, Igor V.,Botov, Evgenij M.,Carlson, Robert M.,Semenova, Irina G.,Fokin, Andrey A.
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p. 8687 - 8691
(2007/10/03)
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- Practical synthesis of benzoxazinones useful as HIV reverse transcriptase inhibitors
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The present invention describes novel methods for the synthesis of benzoxazinone compounds which are useful as human immunodeficiency virus (HIV) reverse transcriptase inhibitors. The benzoxazinone of the formula: is particularly effective in the treatment of HIV.
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- Catalysis of Anilide Ethanolysis by Barium- and Strontium - Ethoxide Pairs and Their Complexes with 18-Crown-6
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The metal-bound ethoxide species that are quantitatively formed upon mixing equimolar amounts of Me4NOEt and alkaline-earth (Ba, Sr) metal salt in ethanol solution are more reactive than free ethoxide in the cleavage of simple activated amides (e.g. N-methyl-2,2,2-trifluoroacetanilide) lacking any donor group for binding to the metal ion. It is suggested that a metal-coordinated solvent molecule acts as a general acid catalyst for expulsion of the aniline leaving group in the rate-determining step. The position of the proton in the transition state is strongly dependent upon structural variations in the aniline portion, as suggested by the magnitude of kinetic solvent isotope effects. Enhanced catalysis is observed upon addition of equimolar amounts of 18-crown-6, which is tentatively interpreted on the basis of the notion that ion pairing is weakened upon cation binding to a crown ether. Important differences concerning metal ion effects in amide vs ester cleavage are pointed out and discussed on the basis of results obtained upon structural modifications of the substrates.
- Cacciapaglia, Roberta,Di Stefano, Stefano,Kelderman, Erik,Mandolini, Luigi,Spadola, Francesco
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p. 6476 - 6479
(2007/10/03)
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- Process for the preparation of alkyl halodifluoroacetates
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For the preparation of alkyl halodifluoroacetates, a 1,1-difluorotetrahaloethane is reacted with an alcohol in the presence of air and/or oxygen and a free-radical initiator, such as for example an azo compound, e.g., azobis(isobutyronitrile).
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- High-yield, radical-initiated oxidative functionalization of ethane by perfluorocarboxylic acid anhydrides. Role of metal ions in catalytic alkane oxidations in the presence of perfluorocarboxylic acid anhydrides
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Hydrogen peroxide and a trace of either ethene or propene initiated the conversion of ethane to propionic acid and its mixed anhydride (CH3CH2CO2H + CH3CH2COOCOCF3) and trifluoromethyl ethyl ketone, CH3CH2COCF3, by trifluoroacetic anhydride at 80 °C. For a fixed amount of H2O2, the amount of products formed increased with increasing amount of trifluoroacetic anhydride employed and was always higher than the amount of H2O2 added. These products were also obtained when H2O2 was replaced by other radical initiators: m-chloroperbenzoic acid, azobisisobutyronitrile, and PbEt4. With PbEt4, ethene or propene was not required for product formation and close to 500 equiv of products was formed for every equivalent of PbEt4 employed! Longer chain perfluorocarboxylic acid anhydrides reacted analogously; however, as the R(f) group increased in length, a corresponding increase in mixed anhydride to ketone selectivity was observed. Methane gave very little product under the reaction conditions whereas propane underwent simple stoichiometric oxidation to 2-propanol and acetone by H2O2. The addition of (CF3CO2)2Pd to the ethane reaction resulted in simple oxidation to ethanol and acetaldehyde in amounts lower than that corresponding to the H2O2 present. In complete contrast to the ethane reaction, the yield of products from methane increased significantly (although less than the H2O2 added) upon the addition of (CF3CO2)2Pd, with methanol being the principal product.
- Hogan, Terrence,Sen, Ayusman
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p. 2642 - 2646
(2007/10/03)
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- Phosphoric-Carboxylic Anhydrides. New Synthetic Procedures and Reactions with Nucleophiles. Reexamination of the Reaction of Se-alkyl-phosphoroselenoates with Alcohols and Mercuric Trifluoroacetate
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Phosphorus trimethylsilyl esters RR'P(O)OSiMe3 react smoothly with carboxylic anhydrides to give phosphoric-carboxylic anhydrides RR'P(O)-O-COR" in excellent yield.A similar reaction proceeds between stannyl esters RR'P(O)OSnMe3 and carboxylic anhydrides.We also have found that the anhydrides RR'P(O)-O-COCF3 are formed in almost quantitative yield when the phosphorus acid halides RR'P(O)X (X=Cl,Br,I) are allowed to react with trifluoroacetic anhydride in the presence of N-methylimidazole. We were able to confirm again that acyclic phosphoric-carboxylic anhydrides exhibit acetylating properties towards amines and alcohols.Our findings contradict with those of Wozniak, Krzyzanowska and Stec relating to the reaction of Se-alkylphosphoroselenoates RR'P(O)SeR" with mercuric trifluoroacetate Hg(OCOCF3)2.Our interpretation of this reaction differs entirely from those presented by the above mentioned authors. Key words: phosphorus-carboxylic anhydrides, Se-alkyl-phosphoroselenoates
- Wasiak, J.,Helinski, J.,Dabkowski, W.,Skrzypczynski, Z.,Michalski, J.
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p. 1027 - 1032
(2007/10/02)
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- DECOMPOSITION OF DIOXIRANES INDUCED BY DIALKYL ETHERS
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Simple dialkyl ethers (i.e. diethyl or dihexyl ether), in addition to undergo oxidative cleavage by reaction with methyl(trifluoromethyl)dioxirane or dimethyldioxirane, induce the decomposition of these oxidation reagents in a concentration dependent manner.The identification of compounds derived from reactions with species such as CH3. or CF3CO2. suggests that the above decomposition is a radical chain process.Key words: Ether, radicals, dimethyldioxirane, methyl(trifluoromethyl)dioxirane.
- Ferrer, Marta,Sanchez-Baeza, Francisco,Casas, Josefina,Messeguer, Angel
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p. 2981 - 2984
(2007/10/02)
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- RUTHENIUM-ASSISTED OXIDATION OF ALKANES IN SOLUTION PHASE
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In the presence of trifluoroacetic acid and dioxygen, some ruthenium(III) β-ketoenolates can convert alkanes to alkyl trifluoroacetates, in some cases selectively and even stereoselectively.
- Diversi, Pietro,Ingrosso, Giovanni,Lucherini, Antonio,Sagramora, Laura,Salvadori, Eleonora
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p. 179 - 180
(2007/10/02)
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- Fragmentation-Rearrangement of 2-Acyloxyalkylphosphonates - a Novel Route to Alkyl Metaphosphate Extrusion
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Thermolysis of dialkyl 2-acyloxyalkylphosphonates, resulting in the fragmentation to an alkene, ester and alkyl metaphosphate, represents the first example of a reaction in which alkyl group migration has to occur before the metaphosphate species can be extruded from the system.
- Jongh, Connie P. de,Modro, Tomasz A.
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p. 1003 - 1004
(2007/10/02)
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- Oxidation of Ethane and Propane with Cobalt(II) Catalyst: Unexpected Formation of 1,2-Diol Esters and C-C Bond Cleavage
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Ethane reacts with both cobalt(III) and O2-cobalt(II) in trifluoroacetic acid solution to form ethyl trifluoroacetate and 1,2-bistrifluoroacetoxyethane in successive reactions, along with the products of C-C bond cleavage; propane undergoes similar oxidative reactions.
- Stolarov, Igor P.,Vargaftik, Michael N.,Shishkin, Dmitry I.,Moiseev, Ilya I.
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p. 938 - 939
(2007/10/02)
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- THERMAL DECOMPOSITION OF PEROXIDE DERIVATIVES OF POLYFLUORINATED β-KETOESTERS
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The thermal flow microcalorimetric method was used to determine the kinetic parameters for the thermal decomposition of peroxide derivatives of polyfluorinated β-ketoesters and the decomposition products were established.
- Rakhimov, A. I.,Chapurkin, V. V.,Val'dman, A. I.,Val'dman, D. I.,Saloutin, V. I.,et al.
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p. 1496 - 1499
(2007/10/02)
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- UNUSUAL REACTION CHEMISTRY IN THERMAL DECOMPOSITION OF ALKALI METAL 2-ALKOXY-2,3,3,3-TETRAFLUOROPROPIONATE SALTS
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Pyrolyses of several salts ROCF(CF3)CO2(-)M(+) (R=Me, Et, CF3CH2; M=Na, K, Cs) have been studied.The reaction chemistry shows highly unusual dependence on the nature of the alkoxy substituent and the metal cation.Product distribution are described along with some proposed mechanisms.
- Pellerite, Mark J.
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- Triazene Drug Metabolites. Part 9. Base Catalysed Deacylation of 3-Acyl-3-alkyl-1-aryltriazenes in Ethanol.
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3-Acyl-3-alkyl-1-aryltriazenes undergo a base-catalysed deacylation reaction to liberate the corresponding cytotoxic 3-alkyl-1-aryltriazene.Reaction are first-order in both and .Second-order rate constants, k2, depend on the structure of both the substrate and the base.The values of k2 for the deformylation of 1-aryl-3-formyl-3-methyltriazenes by piperidine follow the Hammett relationship giving ρ +2.9; a similar correlation, ρ +1.6, is observed for the morpholine catalysed deacylation of 1-aryl-3-methyl-3-trifluoroacetyltriazenes.For 1-(4-cyanophenyl)-3-methyl-3-trifluoroacetyltriazene, a correlation between the aqueous pKa of the base and k2 is obtained, giving a Broensted β value of 0.36.The solvent deuterium isotope effect, k2EtOH/k2EtOD, for the piperidine-catalysed deacylation of 1-(3-pyridyl)-3-formyl-3-methyltriazene is 2.2, and 2,2,6,6-tetramethylpiperidine is some 2.4 times more effective than piperidine at catalysing the deformylation of this compound.Rate constants for the deacylation of 3-alkyltriazenes diminish in the order Me > Pr > Et.Rate constants also vary with the nature of the acyl group: thus CF3CO > HCO > MeCO > C8H17CO.The data are interpreted in terms of a mechanism that involves a rate-determining, general-base-catalysed attack of a solvent ethanol molecule at the carbonyl carbon atom of the group, followed by rapid collapse of the tetrahedral intermediate to form the monoalkyltriazene.
- Iley, Jim,Ruecroft, Graham,Carvalho, Emilia,Rosa, Eduarda
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p. 1264 - 1273
(2007/10/02)
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- Reactions of the Readily Accessible Electrophile, Trifluoroacetyl Triflate: A Very Reactive Agent for Trifluoroacetylations at Oxygen, Nitrogen, Carbon, or Halogen Centers
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Trifluoroacetyl triflate (TFAT) is readily prepared in 82percent yield by the dehydration (phosphorus pentoxide) of a 2:1 mixture of trifluoroacetic acid and trifluoromethanesulfonic (triflic) acid.Reactions of this highly electrophilic trifluoroacetylating reagent with alcohols, ketones, ethers, amines, and pyridines give esters, enol esters, ether cleavage, amides, and acylpyridinium ions, respectively.Reactions with ionic or easily ionizable alkyl halides give the very volatile trifluoroacetyl halides and the ionic triflate.Triphenylmethyl chloride, for example, is quantitatively converted to triphenylcarbenium triflate in a very convenient synthetic procedure.Trifluoroacetyl triflate is used in the synthesis of the first member of a new class of pyrylium salts, 2,6-dimethoxypyrylium triflate.
- Forbus, T. R.,Taylor, S. L.,Martin, J. C.
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p. 4156 - 4159
(2007/10/02)
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- Oxidative Displacement of Halogen from Alkyl Halides by Phenyliodine(III) Dicarboxylates
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The reaction of alkyl iodides with aryliodine(III) dicarboxylates affords as the main product the ester derived through substitution of iodine by an acyloxy group; in some cases α-iodoalkyl esters are also formed along with other minor products.Certain reactive bromides and chlorides react along similar lines.The mechanism of these reactions is briefly discussed.
- Gallos, John,Varvoglis, Anastasios
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p. 1999 - 2002
(2007/10/02)
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- Mononuclear hydrido alkyl carbonyl complexes of osmium and their polynuclear derivatives
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Osmium hydrido alkyl carbonyl complexes cis-Os(CO)4(H)R (R = Me, Et) can be prepared by alkylation of [Os(CO)4H]- with the corresponding alkyl fluorosulfates. The thermal decomposition of these complexes gives dinuclear and trinuclear derivatives HOs2(CO)8R and ROs3(CO)12R. Other dinuclear complexes can be obtained from similar reactions of hydrides with alkyl carbonyl complexes. The course of the reaction of cis-Os(CO)4(H)CH3 with Ph3P depends upon the reaction conditions: with complete exclusion of air (Ph3P)Os(CO)4 and CH4 are obtained, whereas small amounts of air induce the rapid operation of a radical-chain substitution mechanism and the formation of Os(CO)3(PPh3)(H)CH3.
- Carter, Willie J.,Kelland, John W.,Okrasinski, Stanley J.,Warner, Keith E.,Norton, Jack R.
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p. 3955 - 3960
(2008/10/08)
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