- Oxidative Addition of Aryl and Alkyl Halides to a Reduced Iron Pincer Complex
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The two-electron oxidative addition of aryl and alkyl halides to a reduced iron dinitrogen complex with a strong-field tridentate pincer ligand has been demonstrated. Addition of iodobenzene or bromobenzene to (3,5-Me2MesCNC)Fe(N2)2 (3,5-Me2MesCNC = 2,6-(2,4,6-Me-C6H2-imidazol-2-ylidene)2-3,5-Me2-pyridine) resulted in rapid oxidative addition and formation of the diamagnetic, octahedral Fe(II) products (3,5-Me2MesCNC)Fe(Ph)(N2)(X), where X = I or Br. Competition experiments established the relative rate of oxidative addition of aryl halides as I > Br > Cl. A linear free energy of relative reaction rates of electronically differentiated aryl bromides (ρ = 1.5) was consistent with a concerted-type pathway. The oxidative addition of alkyl halides such as methyl-, isobutyl-, or neopentyl halides was also rapid at room temperature, but substrates with more accessible β-hydrogen positions (e.g., 1-bromobutane) underwent subsequent β-hydride elimination. Cyclization of an alkyl halide containing a radical clock and epimerization of neohexyl iodide-d2 upon oxidative addition to (3,5-Me2MesCNC)Fe(N2)2 are consistent with radical intermediates during C(sp3)-X bond cleavage. Importantly, while C(sp2)-X and C(sp3)-X oxidative addition produces net two-electron chemistry, the preferred pathway for obtaining the products is concerted and stepwise, respectively.
- Rummelt, Stephan M.,Peterson, Paul O.,Zhong, Hongyu,Chirik, Paul J.
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supporting information
p. 5928 - 5936
(2021/05/06)
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- Ring Opening of Biomass-Derived Cyclic Ethers to Dienes over Silica/Alumina
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We show that cyclic ethers, such 2-methyltetrahydrofuran (2-MTHF), can undergo dehydration to produce pentadienes over SiO2/Al2O3. The catalyst exhibited reversible deactivation due to coke deposition, with the yield to pentadienes decreasing from 68% to 52% at 623 K over 58 h time on stream. A reaction network for 2-MTHF dehydration was proposed on the basis of the results of space time studies. Pentadienes can be produced directly by a concerted hydride shift and dehydration of carbenium intermediates or indirectly through dehydration of pentanal and pentenol. Reaction kinetics studies were performed at temperatures ranging from 573 to 653 K and 2-MTHF partial pressures from 0.21 to 2.51 kPa. The apparent activation energy barrier for 2-MTHF conversion to pentadienes and the reaction rate order for ring opening were determined to be 74 kJ mol-1 and 0.24, respectively, indicating strong interaction between 2-MTHF and the SiO2/Al2O3 surface. Other solid acids such as γ-Al2O3, H-ZSM-5, and Al-Sn-Beta were found to be active for 2-MTHF dehydration to pentadienes. The rate of ring opening decreased in the order 2,5-dimethyltetrahydrofuran > 2-MTHF > tetrahydropyran > tetrahydrofuran. Over SiO2/Al2O3, the dehydration of 2,5-dimethyltetrahydrofuran resulted in 75% yield to hexadiene isomers. (Figure Presented).
- Kumbhalkar, Mrunmayi D.,Buchanan, J. Scott,Huber, George W.,Dumesic, James A.
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p. 5248 - 5256
(2017/08/17)
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- RENEWABLE ACRYLIC ACID PRODUCTION AND PRODUCTS MADE THEREFROM
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Processes and methods for making biobased acrylic acid products including acrylic acid, acrylic acid oligomers, acrylic acid esters, acrylic acid polymers and articles from renewable carbon resources are described herein.
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Paragraph 00140; 00141; 00142; 00143
(2014/01/08)
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- CATALYTIC DEHYDRATION OF ALCOHOLS AND ETHERS OVER A TERNARY MIXED OXIDE
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A ternary V—Ti—P mixed oxide is shown to catalytically dehydrate 2-methyl-tetrahydrofuran in high conversion to give piperylene, in good yield. Volatile products collected from this reaction contain piperylene in concentrations as high as 80 percent by weight. Dehydration of glycerol to acrolein in high conversion and moderate selectivity is also demonstrated. The catalyst is also shown to dehydrate other alcohols and ether substrates. The catalyst is resistant to deactivation and maintains activity between runs.
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Paragraph 0043; 0046
(2013/03/28)
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- Synthesis and characterization of tridentate schiff base derivative of indenyl lanthanoid chloride tetrahydrofuranate complexes for catalytic applications
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Four kinds of novel lanthanocene complexes were synthesized in reasonable yield by the reaction of equimolar quantity of sodium salt of tridentate Schiff base [N-(2-methoxyphenyl)salicylideneimine] with indenyl lanthanoid dichloride tetrahydrofuranate in tetrahydrofuran. All the complexes after purification were characterized by MS and EA, respectively. These complexes isomerized successfully the 1,5- hexadiene into a mixture of products such as 1,4-hexadiene, 2,4-hexadiene,1,3-hexadiene, methylenecyclopentane and methylcyclopentene. Similarly they also proved effective for the polymerization of methylmethacrylate (MMA), 56.45 % yield and high molecular weight (355 × 103).
- Yousaf, Muhammad,Zahoor, Ameer Fawad,Anjum, Anbreen,Bokhari, Tanveer Hussain,Ali, Kulsoom Ghulam,Purveen, Bushra,Naheed, Shazia,Jabbar, Abdul,Ahmad, Hafiz Badaruddin
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p. 518 - 520
(2013/02/22)
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- SYNTHESIS OF PARA-XYLENE AND TOLUENE
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A method of making para-xylene or toluene is carried out by: (a) reacting a C5 or C6 linear monoene (itself, or formed from a C5 or C6 linear alkane) with a hydrogen acceptor in the presence of a hydrogen transfer catalyst to produce a C5 or C6 diene; (b) reacting the C5-C6 diene with ethylene to produce a cyclohexene having 1 or 2 methyl groups substituted thereon; and then (c) either (i) dehydrogenating the cyclohexene in the presence of a hydrogen acceptor with a hydrogen transfer catalyst to produce a compound selected from the group consisting of para-xylene and toluene, or (ii) dehydrogenating the cyclohexene in the absence of a hydrogen acceptor with a dehydrogenation catalyst, to produce para-xylene or toluene.
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Page/Page column 8
(2012/05/20)
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- Regioselective epoxidation of different types of double bonds over large-pore titanium silicate Ti-β
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Regioselective epoxidation of different types of double bonds located within the cyclic and acyclic parts of bulky olefins has been investigated using large-pore titanium silicate Ti-β in the presence of dilute aqueous H 2O2 as oxidant under mild liquid-phase conditions. Our experimental results revealed that side-chain vinylic double bonds are selectively epoxidized than those in the cyclohexene-ring. The epoxidation tendency of various bulky olefins with different positional and/or geometric isomers over Ti-β follows the order: terminal -CC- > ring -CC- ≈ bicyclic ring -CC- > allylic C - H bond. Unlike 4-vinyl-1-cyclohexene, epoxidation of an equimolar mixture of cyclohexene and 1-hexene under identical conditions using Ti-β exhibits completely different selectivity and product distributions. Steric factor and accessibility of reactants to active Ti-sites are responsible for the observed regioselectivity of bulky alkenes.
- Sasidharan, Manickam,Bhaumik, Asim
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experimental part
p. 60 - 67
(2010/12/18)
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- Specific features of ethylene codimerization with butadiene and isoprene in the presence of systems based on iron acetylacetonate and organoaluminum compounds
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The influence of different factors on the kinetics and selectivity of ethylene codimerization with butadiene and isoprene catalyzed by FeAA3 + AIR3 systems in aromatic solvents was studied. The main products of these transformations were octa- and decatrienes, the codimers of ethylene with butadiene. The reactions between FeAA3 and AlEt3 were studied in model conditions. The data on the yield and composition of gaseous products, as well as the structure of intermediates, were obtained. The assumption that active centers in ethylene codimerization and copolymerization with butadiene and isoprene are alkyl and hydride forms of univalent iron and complexes of zero-valent iron was proved. The scheme of the process suggesting the linear codimerization of ethylene with 1,3-dienes and isomerization of 1,4-hexadiene as a degenerated polymerization with univalent iron hydride as an active center was discussed in detail. The alternative mechanism of ethylene codimerization with 1,3-dienes in the presence of zero-valent iron complexes via the formation of a five-membered iron cycle was also discussed.
- Belova,Matkovskii
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p. 110 - 120
(2007/10/03)
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- Catalytic Hydromagnesation of 1,3-Alkadienes
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Isopropylmagnesium chloride reacts with 1,3-alkadienes with formation of monomeric and linear and cyclic dimeric hydromagnesation products. 1,3-Alkadienes with longer and branched alkyl chains give rise to a smaller fraction of the dimeric products.
- Viktorov,Zubritskii
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p. 1706 - 1711
(2007/10/03)
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- A New Route to 1,3-Dienes: TMSI Elimination of 2-Ene-1,4-diols
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Iodotrimethylsilane effects conversion of acyclic bis-secondary 2-ene-1,4-diols to 1,3-dienes in moderate yield.The reaction with 3-hexene-2,5-diol favors anti elimination but is largely nonstereospecific.
- Hill, Richard K.,Pendalwar, Shekhar L.,Kielbasinski, Karen,Baevsky, Matthew F.,Nugara, Peter N.
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p. 1877 - 1884
(2007/10/02)
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