400-38-4Relevant academic research and scientific papers
Propane activation by palladium complexes with chelating bis(NHC) ligands and aerobic cooxidation
Munz, Dominik,Strassner, Thomas
, p. 2485 - 2488 (2014)
The development of efficient aerobic oxidation methods remains a challenge for the selective functionalization of C-H bonds in alkanes. Herein we report the development of a C-H functionalization procedure for propane by using a palladium catalyst with chelating bis(N-heterocyclic carbene) ligands in trifluoroacetic acid together with a vanadium co-catalyst. Halides play a decisive role in the reaction. The experimental results are presented together with supporting kinetic data and an isotope effect. The reaction can be run with dioxygen as the oxidant if vanadium salts and halides are present in the reaction mixture. Experimental as well as computational results favor a mechanism involving C-H activation by palladium(II), followed by oxidation to palladium(IV) by bromine. Reoxidation by dioxygen: The combination of C-H activation by a homogeneous catalytic palladium complex with a vanadiumoxo co-catalyst allows the selective aerobic oxidation of propane with dioxygen (see scheme). Copyright
On the mechanism of the palladium bis(NHC) complex catalyzed CH functionalization of propane: Experiment and DFT calculations
Munz, Dominik,Strassner, Thomas
, p. 14872 - 14879 (2014)
We report a detailed mechanistic study on the CH functionalization of alkanes by palladium complexes with chelating bis(N -heterocyclic carbene) (NHC) complexes. The experimental results are complemented by detailed DFT calculations, which allow us to rationalize the regioselectivity and the catalytic activity. The study includes a library of catalysts with different electronic and steric properties, kinetic data, and isotope effects. The combined experimental and computational results favor a mechanism involving organometallic palladium(IV) intermediates. Furthermore, it is shown that at high halide loadings a different mechanism is operative.
Aerobic Partial Oxidation of Alkanes Using Photodriven Iron Catalysis
Cao, Yuan,Coutard, Nathan,Goldberg, Jonathan M.,Groves, John T.,Gunnoe, T. Brent,Jeffrey, Philip D.,Jia, Xiaofan,Valle, Henry U.
supporting information, (2022/01/11)
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.
Electrocatalytic Oxyesterification of Hydrocarbons by Tetravalent Lead
Haviv, Eynat,Herman, Adi,Khenkin, Alexander M.,Neumann, Ronny
, p. 10494 - 10501 (2021/08/31)
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.
SN2 and E2 Branching of Main-Group-Metal Alkyl Intermediates in Alkane CH Oxidation: Mechanistic Investigation Using Isotopically Labeled Main-Group-Metal Alkyls
Ess, Daniel H.,Gunsalus, Niles Jensen,Hashiguchi, Brian G.,Konnick, Michael M.,Koppaka, Anjaneyulu,Park, Sae Hume,Periana, Roy A.
, p. 1907 - 1916 (2020/06/08)
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.
Selective Photo-Oxygenation of Light Alkanes Using Iodine Oxides and Chloride
Liebov, Nichole S.,Goldberg, Jonathan M.,Boaz, Nicholas C.,Coutard, Nathan,Kalman, Steven E.,Zhuang, Thompson,Groves, John T.,Gunnoe, T. Brent
, p. 5045 - 5054 (2019/10/28)
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.
Ozone oxidation process of preparing a halogenated acetic acid and esters thereof (by machine translation)
-
Paragraph 0093-0095, (2017/06/29)
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)
A process for the preparation of suitable ester
-
Paragraph 0021-0022, (2020/02/08)
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.
Transfer hydrogenation of ketones, nitriles, and esters catalyzed by a half-sandwich complex of ruthenium
Lee, Sun-Hwa,Nikonov, Georgii I.
, p. 107 - 113 (2015/01/30)
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.
Partial oxidation of light alkanes by periodate and chloride salts
Kalman, Steven E.,Munz, Dominik,Fortman, George C.,Boaz, Nicholas C.,Groves, John T.,Gunnoe, T. Brent
supporting information, p. 5294 - 5298 (2015/03/30)
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
