- Cross coupling reactions of multiple CCl bonds of polychlorinated solvents with Grignard reagent using a pincer nickel complex
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The nickel(II) complex of a bulky pincer-type ligand, N,N′-bis(2,6- diisopropylphenyl)-2,6-pyridinedicarboxamido, was examined for sp 3-sp3 coupling of Grignard reagents with polychlorinated solvents. The nickel(II) complex catalyzed CC coupling of polychlorinated alkyl halides, such as dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), with various Grignard reagents. The effective activation of multiple CCl bonds proceeded under ambient reaction conditions and within a short time (20 min). This catalyst displays the highest activity yet reported for this reaction type, with catalyst loading as low as 0.4 mol% and turnover frequency (TOF) as high as 724 h-1. The catalyst is capable of replacing all chlorine atoms with CC bond formations for all of the polychlorinated solvents under investigation. The catalytic process could prove to be an efficient method of remediation of toxic polychlorinated solvents while generating synthetically and commercially important chemicals.
- Gartia, Yashraj,Nasini, Udaya Bhasker,Ghosh, Anindya,Biswas, Abhijit,Stadler, Matthew
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p. 322 - 327,6
(2020/07/30)
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- A novel iron complex for cross-coupling reactions of multiple C-Cl bonds in polychlorinated solvents with grignard reagents
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A novel iron(III) complex (2) of a pincer ligand [1, N2,N6-bis(2,6- diisopropylphenyl)pyridine-2,6-dicarboxamide] was developed and used for remediation of polychlorinated solvents via sp3-sp3 coupling of Grignard reagents with C-Cl bonds. The use of an iron catalyst for such coupling reactions is highly desirable due to its greener and more economical nature. Complex 2 was characterized using various spectroscopic techniques: electrospray ionization mass spectrometer (ESI-MS, m/z 575.1), cyclic voltammetry (E 1/2, 0.03 V and ΔE, 0.97 V), and ultraviolet visible (UV/Vis) spectroscopic techniques. The iron(III) complex showed efficient activation of multiple C-Cl bonds and catalyzing C-C coupling of polychlorinated alkyl halides, such as dichloromethane (CH2Cl2), chloroform (CHCl3), and carbon tetrachloride (CCl4), with various Grignard reagents under ambient reaction conditions. Complex 2 showed exceptional activity with reactions approaching near completion in about 5 min. With the required catalyst loading as low as 0.2 mol%, considerably high turnover numbers (TON = 483) and turnover frequency (TOF = 5,800 h-1) were obtained. None of the products detected during the reaction contained any chlorine, indicating an efficient dechlorination method while synthesizing products of synthetic and commercial interest. Interestingly, the catalyst was capable of replacing all chlorine atoms in each polychlorinated solvent under the investigations with high conversion. Springer Science+Business Media, LLC 2012.
- Gartia, Yashraj,Pulla, Sharon,Ramidi, Punnamchandar,Farris, Carolina Costa,Nima, Zeid,Jones, Darin E.,Biris, Alexandru S.,Ghosh, Anindya
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p. 1397 - 1404
(2013/01/15)
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- Thermolysis studies on platinacycloalkane complexes
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Thermal decomposition studies on platinacycloalkanes of the type Pt(CH 2)mL2 (where m = 6,7,8,10 and L2 = dppp {1,3-bis(diphenylphosphino)propane}, dppe {1,2-bis(diphenylphosphino) ethane} or L = PPh3, tBu3P) are described. The results reveal that the organic product distribution depends on various factors such as the nature of ligand, the metal system, the mode of decomposition, the ring size and the temperature. Possible mechanistic pathways for the formation of various products are discussed. These platinacycloalkanes can be used as models for metallacycloalkane intermediates in catalytic reactions.
- Zheng, Feng,Sivaramakrishna, Akella,Moss, John R.
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scheme or table
p. 2457 - 2465
(2011/06/26)
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- Kinetics of the Thermal Isomerizations of Gaseous Cycloheptene and Cyclooctene
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Single-pulse shock tube kinetic studies of the thermal isomerizations of gaseous cycloheptene (CHEP) and cis-cyclooctene (COCT), and static reactor isomerizations of COCT at lower temperatures, have revealed a mechanistic dissimilarity in the two superficially analogous cycloalkene to, α,ω-alkadiene reactions observed.At 1035-1256 K, CHEP produced mostly vinylcyclopentane, log10(k,s-1) = 15.1 (+/- 0.7) - 69.7 (+/- 3.3) x 103/4.576T, and some 1,6-heptadiene.From COCT, heated over the range 610-1091 K, the dominant product was 1,7-octadiene, log10(k,s-1) = 13.8 (+/- 0.2) -54.6 (+/- 0.5) x 103/4.576T, with small amounts of vinylcyclohexane formed at the higher temperatures, log10(k,s-1) = 15.2 (+/- 0.3) - 64.4 (+/- 1.2) x 103/4.576T.The activation energy for the COCT isomerization to 1,7-octadiene is too low to associate with formation of a diradical, but is consistent with a concerted retro-ene mechanism.The higher activation energy isomerization to vinylcyclohexane, however, passes through a diradical transition structure.In contrast, the structure of CHEP is not adaptable to a concerted retro-ene precess, and both 1,6-heptadiene and vinylcyclopentane are formed through diradical-mediated reactions.
- Kalra, Bansi L.,Afriyie, Yau,Brandt, Benjamin,Lewis, David K.,Baldwin, John E.
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p. 8142 - 8146
(2007/10/02)
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- KINETICS AND MECHANISM OF SOME VINYL RADICAL CYCLISATIONS
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The vinyl radicals 2a, 2b, and 11 each undergo fast exo ring closure to give 5a, 5b, and 12, the first two of which readily rearrange to ring-expanded radicals.
- Beckwith, Athelstan L.J.,O'Shea, Dennis M.
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p. 4525 - 4528
(2007/10/02)
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- 1,4-CYCLOHEPTYLENE AND THE RELATED ALLYLIC DIRADICALS. THERMAL NITROGEN EXTRUSION FROM 6,7-DIAZABICYCLONON-6-ENES
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Thermal nitrogen extrusion of 2-methylene-6,7-diazabicyclonon-6-enes and 6,7-diazabicyclonona-2,6-dienes proceeded easily to give closure and cleavage products via the corresponding 5-methylene-1,4-cycloheptylenes and 4-cyclohepten-1,3-ylenes, respectively.
- Uyehara, Tadao,Takahashi, Masayuki,Kato, Tadahiro
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p. 1241 - 1244
(2007/10/02)
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- PHEROMONE 511): SYNTHESE VON UNGESATTINGEN PHEROMONKETONEN AUS ORGYIA PSEUDOTSUGATA (DOUGLAS FIR TUSSOCK MOTH) UND CARPOSINA NIPONENSIS (PEACH FRUIT MOTH) (LEPIDOPTERA)
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The principal (9, 27) and minor (17, 28) sex pheromone components of both, the Douglas fir tussock moth (orgyia pseudotsugata) and the peach fruit moth (Carposina niponensis), have been synthesized in four steps each, using the chain-lengtheningdifunctionalisation of Grignard reagents by reaction with ketenylidenetriphenylphosphorane as the key step.
- Bestmann, Hans Jurgen,Schmidt, Martin
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p. 6171 - 6174
(2007/10/02)
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- Photochemistry of Alkenes. 6. Direct Irradiation of 1,5-Hexadienes: and Sigmatropic Allyl Shifts
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The photochemical behavior of a series of alkyl-substituted 1,5-hexadienes has been studied.Competing allylcyclopropane formation and rearrangement to an isomeric 1,5-hexadiene via competing and sigmatropic allyl shifts, respectively, were observed.In one case a product (30 from 27) and in another a product (35 from 31) was obtained, but only in low yield.Extensive cis trans isomerization competed with the allyl shifts, and, in addition, other products were obtained which are characteristic of the photochemical behavior of isolated double bonds.At low conversion diene 10t underwent stereoselective rearrangement to 8t and 11t, whereas the cis isomer 10c afforded mixtures of the cis and trans isomers of 8 and 11.Attempts to induce the allyl migrations by sensitization with p-xylene or by irradiation at 254 nm afforded only cis trans isomerization.It is concluded that the allyl migrations occur via an excited state involving interaction between the double bonds and requiring a conformation in which the central C3-C4 bond is in a plane orthogonal to both double bonds, as proposed previously.In contrast with the acyclic dienes, 1,5-cyclooctadiene (50) afforded products 51-53 from competing , , and allyl shifts, respectively.The divergent behavior in this case apparently arises because appropriate interaction between the two double bonds can occur only in the boat conformation.
- Manning, T. D. R.,Kropp, Paul J.
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p. 889 - 897
(2007/10/02)
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- The Nature of the Preferred Chain-carrying Metallacarbene Intermediate in Metathesis Reactions Involving Alk-1-enes
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The minor products from the cross-metathesis of norbornadiene (NBD) with hex-1-ene and of cyclopentene (CP) with octa-1,7-diene (1,7-OD), respectively, show that the complexed alkylidenes, RCH= (where denotes the metal site with the ligands attached), are much preferred to the complexed methylene, CH2=, as chain carriers formed by the reactions of the terminal olefins; but CH2=, when formed, is highly reactive towards the latter, with the strongly electrophilic methylene ligand selectively adding to the terminal olefins at the C-1 position.
- Bencze, Lajos,Ivin, Kenneth J.,Rooney, John J.
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p. 834 - 835
(2007/10/02)
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