- Study of reactions of some halides, cyclopentadienyl dichlorides, and bis(cyclopentadienyl) chlorides of lanthanides with trans-stilbene adducts with alkali metals [PhCHCHPh].-M+ (M = Li, Na)
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Reaction of Sml2(THF)2 with metallic lithium and trans-stilbene in 1 : 2 : 2 ratio in DME gives the stilbene complex of divalent samarium (PhCHCHPh)Sm(DME)2. This complex reacts with hydrogen in THF to give SmH2(THF)2 and 1,2-diphenylethane. The reaction with (Me3Si)2NH gives the amide [(Me3Si)2N]2Sm(DME)2 and the reaction with triphenylgermane yields Ph3GeGePh3. Reaction of CpLuCl2(THF)2 with 2 equivalents of [PhCHCHPh].- Na+ in DME results in the dimerization of stilbene fragments to give an ate-complex {Cp2Lu[μ-CH(Ph)CH(Ph)CH(Ph)CH(Ph)]}Na(DME)3. In the reaction of Cp2GdCl with [PhCHCHPh].- Na+, the known complex Cp3Gd(THF) was isolated as the only lanthanide-containing product.
- Trifonov,Fedorova,Kirillov,Bochkarev,Girgsdies,Schumann
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p. 1436 - 1439
(2007/10/03)
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- Photochemistry of Stilbene-Amine. Spin-Trapping Study
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2-Methyl-2-nitrosopropane (MNP) was used as a spin-trap reagent to study the radicals formed in the photochemical reaction of substituted trans-stilbenes (TS) with tertiary amines.Seven 1,2-(p,p'-disubstituted phenyl)ethyl radicals were trapped by MNP and isolated and identified by HPLC-EPR.The nitrogen hyperfine splitting constants (hfsc) of these radicals are linearly correlated with the Hammett substituent constants δp.There is also a linear correlation of the nitrogen hfsc with both the single δp parameter and the dual δR, δ1 parameters.The inductive and resonance effects are of equal importance.The correlation between proton hfsc and a single δp parameter is not linear.There is fair correlation between the β-proton hfsc and the dual parameters δR, δ1.The only fair correlation may be due to the large dihedral angle between the nitrogen ? orbital and the N-C-H plane.
- Lin, Chiou-Rong,Wang, Cheng-Nan,Ho, Tong-Ing
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p. 5025 - 5029
(2007/10/02)
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- ELECTRO-ORGANIC REACTIONS. PART 29: CATHODIC REDUCTION ACTIVATED BY ARENE-CHROMIUM TRICARBONYL COMLEXATION
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Chromium tricarbonyl-arene complexes are easily reduced electrochemically and reduction potentials ca. 0.6 V less than the corresponding arenes; hence stilbene is activated towards hydrodimerisation and phenanthrene towards hydrogenation
- Chiu, Y. Lin,Sant'ana, Antonio E. G.,Utley, James H. P.
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p. 1349 - 1352
(2007/10/02)
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- Photochemical Reaction of 1,4-Naphthalenedicarbonitrile with Alkylbenzenes and Bibenzyls
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The photochemical reaction of 1,4-naphthalenedicarbonitrile with some alkylbenzenes and bibenzyls has been examined.A unitary mechanistic picture is formulated on the basis of product study, deuteration experiments, and fluorescence and reaction quantum yield measurements.Proton transfer within the singlet radical ion pair followed by in-cage cycloaddition of the two radicals yields stereoselectively 5,11-methanodibenzo cyclooctene derivatives (8).Reaction of benzyl radicals (formed by protolysis or, for radical cations having no benzylic proton, by C-C bond cleavage) with unprotonated NDN.- leads, again stereoselectively, to 2-benzyl-1,2-dihydronaphtalenes (9).Escape of the donor radical cation and following C-H or C-C bond cleavage leads to a different product, thus, benzyl radicals are trapped by NDN to yield substitution products (11) or recombine.Benzyl cations are trapped by nucleophiles.
- Albini, Angelo,Fasani, Elisa,Mella, Mariella
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p. 4119 - 4125
(2007/10/02)
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- Phosphinomethyl Zirconium(III) Complexes as Hydrogenation Catalysts of Specific Selectivity
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Zirconium(III) complexes containing the chelated moiety hydrogenate unsaturated hydrocarbons in a rapid catalytic process with specific selectivity, givihg a quantitative yield of cyclo-octene from 1,3- and 1,5-cyclo-octadiene and 1,2,3,4-tetraphenylbutane from diphenylacetylene.
- Choukroun, Robert,Basso-Bert, Mario,Gervais, Daniele
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p. 1317 - 1319
(2007/10/02)
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- The Effect of Substituents on the Photochemical Reaction between Naphtalenedicarbonile and Methylbenzenes
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The photochemical reaction between 1,4-naphtalenedicarbonile (NDN) and toluene in acetonitrile is extended to bibenzyl (4), 3- and 4-fluorotoluene (8, 7), and 3- and 4-methoxytoluene (9, 10).The product distribution obtained with compounds 4, 7 and 10 is
- Albini, Angelo,Fasani, Elisa,Montessoro, Ezio
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p. 1409 - 1415
(2007/10/02)
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- Photochemical Addition of Tertiary Amines to Stilbene. Free-Radical and Electron-Transfer Mechanisms for Amine Oxidation
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Several amines of structure Me2NCH2R, where R = CH=CH2, CO2Et, CCCH3, and CCH, but not Ph, react with the singlet state of trans-stilbene in hexane solution to yield adducts of structure PhCH2CHPhCHRNMe2.In acetonitrile solutions, these adducts are accompanied by variable amounts of adducts of structure PhCH2CHOPhCH2NMeCH2R.Both types of adduct are formed by cross combination of 1,2-diphenylethyl-α-aminoalkyl radical pairs.The mechanism of radical pair formation is concluded to be solvent dependent.In nonpolar solvents, hydrogen atom transfer selectively yields a merostabilized α-aminoalkyl radical.In polar solvents, a sequential electron-transfer, proton-transfer mechanism yields both α-aminoalkyl radicals.
- Lewis, Frederick,Ho, Tong-Ing,Simpson, J. Thomas
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p. 1924 - 1929
(2007/10/02)
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- Photochemical Addition of Tertiary Amines to Stilbene. Stereoelectronic Control of Tertiary Amine Oxidation.
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The photochemical addition reactions of seven nonsymmetrical tertiary amines with singlet trans-stilbene are described.Addition of methyldiisopropylamine or isopropyldimethylamine is highly selective for formation of the least substituted α-amino radical, whereas addition of several less highly branched amines is relatively nonselective.The product isotope effect for tert-butylmethyl(trideuteriomethyl)amine is 2.2+/-0.2.Product selectivity is determined by the orientation of the deprotonation of an aminium radical intermediate by the stilbene radical anion.Selectiveoxidation results from e stereoelectronic effect which is most evident w hen one more alkyl group is highly branched.
- Lewis, Frederick D.,Ho, Tong-Ing,Simpson, J. Thomas
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p. 1077 - 1082
(2007/10/02)
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- Liquid-Phase Pyrolysis of 1,2-Diphenylethane
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This paper presents results of a kinetic study of the deconposition of 1,2-diphenylethane in the liquid phase between 350 and 425 deg C along with a through mechanistic analysis of this system using thermochemical kinetics analysis and computer modeling.Toluene, trans-1,2-diphenylethene, and 1,1-diphenylethane are important products throughout the range of decomposition studied, with 1,2,3,4-tetraphenybutane being a major product in the early stages of reaction and diphenylmethane becoming important after extensive decomposition.Some noteworthy aspects of this reaction are the following: (1) all major product in the early stages of reaction can be quantitatively accounted for by a free-radical reaction model employing reasonable kinetic parameters; (2) trans-1,2-diphenylethene is formed by both a direct and indirect route involving α-1,2-diphenylethyl radicals; (3) 1,1-diphenylethane appears to be formed by a thermodynamically uphill 'neophyl' rearrangement; (4) above 10percent reaction secondary reactions lead to formation of diphenylmethane and noticeable divergence of predicted and observed product concentrations.This work presents the first use of thermochemical kinetics principles for analysis of complex liquid phase pyrolytic reactions and represents a first step toward establishing a reliable and self-consistent set of rate parameters for interpretation of these reactions.
- Miller, R.E.,Stein, S. E.
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p. 580 - 589
(2007/10/02)
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