- 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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p. 1907 - 1916
(2020/06/08)
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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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- 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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- Ortho-Phenylene bridged palladium bis-N-heterocyclic carbene complexes: Synthesis, structure and catalysis
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A series of ortho-phenylene bridged palladium bis-NHC complexes has been synthesized. Complexes with imidazolium and benzimidazolium derived NHCs and methyl-/benzyl-wingtips are reported. Bis(benz)imidazoles with a doubly brominated ortho-phenylene bridge could be obtained by an electrophilic substitution reaction. The structure of the complexes could be confirmed by three solid-state structures. All catalysts have been tested in the catalytic functionalisation of propane. The catalytic activity is highly dependent on the ligand, whereas ligand effects on the regioselectivity (n/iso) are much smaller.
- Munz, Dominik,Poethig, Alexander,Tronnier, Alexander,Strassner, Thomas
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p. 7297 - 7304
(2013/07/11)
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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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