- Method for hydrocarbylation synthesis of trisubstituted and tetrasubstituted olefins from non-terminal olefins
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The invention discloses a method for hydrocarbylation synthesis of trisubstituted and tetrasubstituted olefins from non-terminal olefins, wherein the method comprises the steps: carrying out hydrocarbylation reaction on the non-terminal olefins and sulfoxide in the presence of ferric salt and hydrogen peroxide, carrying out one-pot reaction on disubstituted non-terminal olefins to generate the trisubstituted olefins, and carrying out one-pot reaction on the trisubstituted non-terminal olefins to generate the tetrasubstituted olefins. In the method, sulfoxide is simultaneously used as a hydrocarbylation reagent and a solvent of olefins, and one more hydrocarbyl substituent is added to a reaction product compared with a double-bond carbon atom of a reactant, so that an olefin carbon chain isincreased; the reaction conditions are mild, the selectivity is good, the yield is high, and industrial production is facilitated.
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Paragraph 0054-0063; 0079-0081
(2021/02/06)
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- Synthesis of Allylboronates via Zweifel-type Deprotonative Olefination
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A method for the synthesis of allylboronates via Zweifel-type deprotonative olefination was demonstrated. Tetrasubstituted vinylboronates were used as the substrates. NCS (N-chlorosuccinimide) was used as a bifunctional additive, electrophile and base. This method exhibited a different elimination strategy in Zweifel type transformation to afford allylboronates. The homo-alcohols and alkenes were stereoselective synthesized from the obtained allylboronates, demonstrating the synthetic value of this methodology. (Figure presented.).
- Xu, Nuo,Xu, Jianeng,Zhu, Qing,Liu, Chao
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supporting information
p. 2403 - 2407
(2020/12/30)
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- Method for synthesizing alkyl olefin through coupling of double-bond carbon-hydrogen bond and saturated carbon-hydrogen bond
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The invention discloses a method for synthesizing alkyl olefin through coupling of a double-bond carbon-hydrogen bond and a saturated carbon-hydrogen bond. According to to the method, one-pot reactionis implemented on olefin and sulfoxide in the presence of ferric salt and hydrogen peroxide to generate alkyl olefin; in the method, sulfoxide is simultaneously used as a hydrocarbylation reagent anda solvent of olefin, and a reaction product is alkyl olefin from sulfoxide alkyl coupled with olefin carbon atoms, so that an olefin carbon chain is increased; the reaction conditions are mild, the selectivity is good, the yield is high, and industrial production is facilitated.
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Paragraph 0070-0073; 0096
(2021/02/10)
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- Spiro[1,2]oxaphosphetanes of nonstabilized and semistabilized phosphorus ylide derivatives: Synthesis and kinetic and computational study of their thermolysis
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A series of tri- and tetrasubstituted spiro-oxaphosphetanes stabilized by ortho-benzamide (oBA) and N-methyl ortho-benzamide (MoBA) ligands have been synthesized by the reaction of Cα,Cortho-dilithiated phosphazenes with aldehydes and ketones. They include enantiopure products and the first example of an isolated oxaphosphetane having a phenyl substituent at C3 of the ring. Kinetic studies of their thermal decomposition showed that the process takes place irreversibly through a polar transition state (ρ = -0.22) under the influence of electronic, [1,2], [1,3] steric, and solvent effects, with C3/P-[1,2] interactions as the largest contribution to ΔG of olefination. Inversion of the phosphorus configuration through stereomutation has been observed in a number of cases. DFT calculations showed that oBA derivatives olefinated through the isolated (N, O)(Ph, C6H4, C) oxaphosphetanes (Channel A), whereas MoBA compounds decomposed faster via the isomer (C6H4, O)(C, N, Ph) formed by P-stereomutation involving a MB2 permutational mechanism (Channel B). The energy barrier of P-isomerization is lower than that of olefination. Fragmentation takes place in a concerted asynchronous reaction. The thermal stability of oxaphosphetanes is determined by strong C3/P-[1,2] interactions destabilizing the transition state of olefination. The effect of charge distribution and C3/C4-[1,2] and C4/P-[1,3] steric and solvent interactions on ΔG was also evaluated.
- López, Jesús García,Sansores Peraza, Pablo M.,Iglesias, María José,Roces, Laura,García-Granda, Santiago,Ortiz, Fernando López
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p. 14570 - 14591
(2020/11/20)
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- Conversion of Carbonyl Compounds to Olefins via Enolate Intermediate
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A general and efficient protocol to synthesize substituted olefins from carbonyl compounds via nickel catalyzed C—O activation of enolates was developed. Besides ketones, aldehydes were also suitable substrates for the presented catalytic system to produce di- or tri- substituted olefins. It is worth noting that this approach exhibited good tolerance to highly reactive tertiary alcohols, which could not survive in other reported routes for converting carbonyl compounds to olefins. This method also showed good regio- and stereo-selectivity for olefin products. Preliminary mechanistic studies indicated that the reaction was accomplished through nickel catalyzed C—O activation of enolates, thus offering helpful contribution to current enol chemistry.
- Cao, Zhi-Chao,Xu, Pei-Lin,Luo, Qin-Yu,Li, Xiao-Lei,Yu, Da-Gang,Fang, Huayi,Shi, Zhang-Jie
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supporting information
p. 781 - 785
(2019/06/24)
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- Catalytic Functionalization of Styrenyl Epoxides via 2-Nickela(II)oxetanes
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Low-valent nickel is shown to preferentially isomerize mono- or disubstituted epoxides into their corresponding aldehydes. Experiments with tetrasubstituted epoxides demonstrate that these reactions proceed via reactive 2-nickelaoxetane intermediates, and
- Desnoyer, Addison N.,Geng, Jialing,Drover, Marcus W.,Patrick, Brian O.,Love, Jennifer A.
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supporting information
p. 11509 - 11512
(2017/08/30)
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- Nickel-Catalyzed Direct Synthesis of Aryl Olefins from Ketones and Organoboron Reagents under Neutral Conditions
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Nickel-catalyzed addition of arylboron reagents to ketones results in aryl olefins directly. The neutral condition allows acidic protons of alcohols, phenols, and malonates to be present, and fragile structures are also tolerated.
- Lei, Chuanhu,Yip, Yong Jie,Zhou, Jianrong Steve
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supporting information
p. 6086 - 6089
(2017/05/08)
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- Metal-free oxidative cross-coupling of diazirines with arylboronic acids
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We report herein a metal-free cross-coupling of diazirines with arylboronic acids under oxidative conditions. The reaction affords a series of substituted olefins. It is proposed that the interaction between the nitrogen on diazirine with arylboronic acid plays a key role in this transformation.
- Wu, Guojiao,Zhao, Xia,Ji, Wenzhi,Zhang, Yan,Wang, Jianbo
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p. 1961 - 1963
(2016/02/05)
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- Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes
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Reactions of dihetaryl and aryl/hetaryl thioketones with 2-diazopropane, diazoethane, and (trimethylsilyl)diazomethane were studied at variable temperature. The experiments showed that reactions with 2-diazopropane carried out at -75°C occur mainly via th
- Mlostoń, Grzegorz,Pipiak, Paulina,Heimgartner, Heinz
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p. 715 - 724
(2016/07/06)
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- Pt-Catalyzed Rearrangement of Oxaspirohexanes to 3-Methylenetetrahydrofurans: Scope and Mechanism
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A novel Pt-catalyzed rearrangement of oxaspirohexanes to 3-methylenetetrahydrofurans is reported. Mechanistic studies by 13C-labeling experiments confirm oxidative addition of Pt(II) regioselectively to the least substituted carbon-carbon bond
- Malapit, Christian A.,Chitale, Sampada M.,Thakur, Meena S.,Taboada, Rosa,Howell, Amy R.
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p. 5196 - 5209
(2015/05/27)
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- SnCl4-Zn: A novel reductive system for deoxygenative coupling of aliphatic, aromatic, chalcone epoxide, and indanone carbonyl compounds to olefins
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SnCl4-Zn complex provided a novel reductive system in the deoxygenative cross-coupling of aliphatic, aromatic, chalcone epoxide and indanone carbonyl compounds to olefins in high yield (55-86%) at reflux temperature in THF. The advantage of this reagent is inexpensive, short reaction time, and high yield compared to the reagents used in the McMurry cross-coupling reaction.
- Pathe, Gulab Khushalrao,Ahmed, Naseem
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supporting information
p. 1555 - 1561
(2015/03/14)
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- Palladium- and nickel-catalyzed kumada cross-coupling reactions of gem -difluoroalkenes and monofluoroalkenes with Grignard reagents
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A novel Kumada-Tamao-Corriu cross-coupling reaction of gem-di- or monofluoroalkenes with Grignard reagents, with or without β-hydrogen atoms, in the presence of a catalytic amount of palladium- or nickel-based catalysts has been developed. The reaction is performed under mild conditions (room temperature or reflux in diethyl ether for 1-2 h) and leads to di-cross- or mono-cross-coupled products in good to high yields.
- Dai, Wenpeng,Xiao, Juan,Jin, Guanyi,Wu, Jingjing,Cao, Song
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p. 10537 - 10546
(2015/02/19)
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- A one-pot cross-pinacol coupling/rearrangement procedure
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A new catalytic retro-pinacol/cross-pinacol reaction, followed by subsequent rearrangement or deoxygenation of the intermediately formed vicinal diols, is described. This operationally simple one-pot protocol allows isolation of geminal α,α-diphenyl ketones or 1,1-diphenyl alkenes with high yields and selectivities. Copyright
- Scheffler, Ulf,Mahrwald, Rainer
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p. 1970 - 1975,6
(2012/12/12)
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- Mechanisms of stereomutation and thermolysis of spiro-1,2-oxaphosphetanes: New insights into the second step of the wittig reaction
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The experimentally observed stereomutation of spiro-1,2-oxaphosphetanes is shown by DFT calculations to proceed through successive MB2 or M B4 and MB3 mechanisms involving two, four, and three Berry pseudorotations at phosphorus, respectively. Oxaphosphetane decomposition takes place in a single step via a polar transition state. The calculated activation parameters for this reaction are in good agreement with those determined experimentally.
- García López, Jesús,Morán Ramallal, Antonio,González, Javier,Roces, Laura,García-Granda, Santiago,Iglesias, María José,O?a-Burgos, Pascual,López Ortiz, Fernando
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supporting information
p. 19504 - 19507
(2013/02/22)
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- 1,3-Dilithio-2-(diphenylmethylene)propane
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The reaction of 2,2-diphenylmethylenecyclopropane (5) with an excess of lithium and a catalytic amount of DTBB (4 mol %) in THF at -78 °C leads to the formation of dilithiated species 6-8 by reductive opening of the cyclopropane ring. Further reaction of these intermediates with different electrophiles [E = H2O, D2O, CH2{double bond, long}CMeCH2Cl, Me3SiCl, Me3SiCH2Cl, t-BuCHO, Me2CO, Et2CO, n-Pr2CO, i-Pr2CO, t-Bu2CO, (CH2)5CO, Ph2CO and adamantanone] is highly regioselective, yielding exclusively the corresponding products 9, after hydrolysis with water. However, when 3-chloro-2-(chloromethyl)propene (14) is used as a dielectrophile, the cyclisation to give a six-membered ring takes place through intermediate 6, giving compound 16 as the only reaction product.
- Lillo, Victor J.,Gómez, Cecilia,Yus, Miguel
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p. 5182 - 5185
(2008/12/20)
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- Homogeneous decatungstate-catalyzed photooxygenation of tetrasubstituted alkenes: A deuterium kinetic isotope effect study
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The decatungstate W10O324- homogeneous photocatalyzed oxygenation of tetrasubstituted alkenes has been mechanistically studied. In all cases, allylic hydroperoxides are the major products. The primary inter- and intramolec
- Lykakis, Ioannis N.,Vougioukalakis, Georgios C.,Orfanopoulos, Michael
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p. 8740 - 8747
(2007/10/03)
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- 3,5-Bis(trifluoromethyl)phenyl sulfones in the Julia-Kocienski olefination - Application to the synthesis of tri- and tetrasubstituted olefins
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3,5-Bis(trifluoromethyl)phenyl (BTFP) sulfones 8a-d are successfully employed in the modified Julia olefination reaction with carbonyl compounds employing phosphazene base P4-tBu at room temp. in THF, affording tri- and tetrasubstituted olefins in good yi
- Alonso, Diego A.,Fuensanta, Monica,Najera, Carmen
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p. 4747 - 4754
(2007/10/03)
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- Aliphatic thiocarbonyl ylides and thiobenzophenone: Experimental study of regiochemistry and methylene transfer in cycloadditions
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1,3-Dipolar cycloadditions of aliphatic or alicyclic thiocarbonyl ylides 3A-D - sterically hindered at least at one terminus - with thiobenzophenone produce both regioisomeric 1,3-dithiolanes 4 and 5. According to quantum-chemical calculations (preceding paper), a concerted cycloaddition furnishing 2,4-substituted dithiolanes 4 competes with the formation of an intermediate C,C-biradical 9 which cyclizes to the more crowded 4,5-substituted dithiolanes 5. When steric hindrance of 3 increases, the cycloaddition is superseded by 'methylene transfer', i.e., the transfer of the less hindered terminus of 3E-J to the S-atom of thiobenzophenone. The thiobenzophenone S-alkylide 11, thus formed, rapidly reacts with a second molecule ofthiobenzophenone to generate the 4,4,5,5-tetraphenyl-1,3-dithiolane 12 via the highly stabilized C,C-biradical 10. Methylene transfer occurs when the cyclization of the mixed C,C-biradical 9 requires a higher activation barrier than its dissociation to aliphatic thioketone + 11; the threshold is surprisingly well reproduced by calculations. The structural assignment of sixteen 1,3-dithiolanes is based on their formation from corresponding reactant pairs as well as on 1H and 13C chemical shifts. X-ray diffraction analyses of three spiro-1,3-dithiolanes reveal the van der Waals strain in non-bonded interactions, folding angles, shearing forces, and bond lengths. Comparison of the mass spectra of many 1,3-dithiolanes allows the reconstruction of major fragmentation pathways. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Huisgen, Rolf,Mloston, Grzegorz,Giera, Henry,Langhals, Elke,Polborn, Kurt,Sustmann, Reiner
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p. 1519 - 1531
(2007/10/03)
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- Microwave-assisted coupling of carbonyl compound: An efficient synthesis of olefin
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Self-coupling of various ketones and aldehyde as well as mixed coupling of ketones employing TiCl4/Zn under microwave irradiation has been carried out to afford the corresponding olefins.
- Ramana,Singh,Parihar
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p. 760 - 761
(2007/10/03)
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- InCl3-Zn. A novel reduction system for the deoxygenative coupling of carbonyl compounds to olefins
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A simple and inexpensive procedure for the deoxygenative homo-coupling and cross-coupling of carbonyl compounds with InCl3-Zn system in dry acetonitrile at ambient pressure is achieved. The procedure gives excellent yields of E-olefinic products.
- Barman,Thakur,Prajapati,Sandhu
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p. 515 - 516
(2007/10/03)
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- Cationic and neutral diphenyldiazomethanerhodium(I) complexes as catalytically active species in the C-C coupling reaction of olefins and diphenyldiazomethane
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Cationic rhodium(I) complexes cis-[Rh(acetone)2(L)(L')]+ (2: L=L'=C8H14; 3: L=C8H14; L'=PiPr3; 4: L= L'=PiPr3), prepared from [{RhCl-(C8H14)
- Werner, Helmut,Schneider, Michael E.,Bosch, Marco,Wolf, Justin,Teuben, Jan H.,Meetsma, Auke,Troyanov, Sergei I.
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p. 3052 - 3059
(2007/10/03)
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- A new method for reductive coupling of carbonyl compounds to olefins
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Aromatic and aliphatic aldehydes and ketones react with AlCl3-Zn in acetonitrile to yield olefins in good yield. (C) 2000 Published by Elsevier Science Ltd.
- Kumar Dutta,Konwar
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p. 6227 - 6229
(2007/10/03)
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- Characterization of persistent intermediates generated upon inclusion of 1,1-diarylethylenes within CaY zeolite: Spectroscopy and product studies
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Inclusion of 1,1-diarylethylenes within activated CaY results in the formation of colored samples that are stable for prolonged periods. For example, diphenylethylene generates a green color within CaY. Two reactive intermediates have been shown to be res
- Lakshminarasimhan,Thomas,Brancaleon,Wood,Johnston,Ramamurthy
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p. 9247 - 9254
(2007/10/03)
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- Excited Precursor Reactivity, Fast 1,2-H Shifts, and Diffusion-Controlled Methanol Insertion in 1,2-Diphenylalkylidenes
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The photochemistry of several arylalkyldiazo compounds has been investigated by steady-state direct and triplet sensitized irradiations and by nanosecond laser flash photolysis. Steady-state photolyses in methanol yielded methyl ethers and alkenes as the only significant products. Ethers were formed by denitrogenation of the diazo compound followed by carbene insertion into the MeO-H bond, and alkenes were obtained by 1,2-R (R = H,Ph) migrations both in the free carbene and in the singlet excited state of the diazo precursor. Evidence for the exited-state precursor reaction came from differences in product yields as a function of excitation wavelength and excited-state multiplicity. The yields of methyl ethers increased with increasing excitation wavelengths and were greatest upon triplet-state sensitization but were never the sole products formed despite expected diffusion-controlled insertion rates. Accordingly, the formation of pyridine ylides analyzed by laser flash photolysis in the presence of high concentrations of the base yielded relatively modest transient absorptions. The kinetics of the 1,2-H reaction, analyzed by time-resolved detection of stilbene in the case of 1,2-diphenylethylidenes, displayed fast and slow components. The fast component was attributed to stilbene that formed from the excited-state precursor and from the originally formed singlet carbene within the 20 ns pulse. The long-lived component was attributed to a spin-state equilibrated carbene with a lifetime of 70-80 ns in fluorocarbon solvents. Analysis of the long-lived component by a Stern-Volmer treatment upon addition of MeOH gave a lower limit for the reaction rate constant with a value of k1,2-H > 5 × 109 s-1 in a mixed Freon-methanol solvent. It is concluded that the combined effect of phenyl substituents at the carbon bearing the migrating group and high solvent polarity can lead to intramolecular 1,2-H shifts and 1,2-Ph migrations that are fast enough to compete with diffusion-controlled intermolecular MeO-H insertion in concentrated MeOH solutions.
- Motschiedler, Krista,Gudmundsdottir, Anna,Toscano, John P.,Platz, Matthew,Garcia-Garibay, Miguel A.
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p. 5139 - 5147
(2007/10/03)
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- Activation conditions play a key role in the activity of zeolite CaY: NMR and product studies of Bronsted acidity
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CaY, activated under different conditions, was characterized with 1H, 31P, and 1H/27A] double resonance MAS NMR. The 1H MAS NMR spectra of CaY, calcined in an oven at 500 °C, shows resonances from H2O (bound to Ca2+ and the zeolite framework), CaOH+, aluminum hydroxides, silanols, and Bronsted acid sites. No evidence for Lewis acidity is observed on adsorption of trimethylphosphine, and an estimate of ≈16 Bronsted acid sites per unit cell is obtained for this sample. CaY activated in an oven at higher temperatures contains less water, but all the other species are still present. In contrast, CaY activated by slow ramping of the temperature under vacuum to 500 or 600 °C shows a much lower concentration of Bronsted acid sites (1/unit cell). Again, no evidence for Lewis acidity was observed. These NMR results have been utilized to understand the very different product distributions that are observed for reactions of 1,1- and 1,2-diarylethylenes in zeolite CaY activated in an oven (in air) and under vacuum. Samples with high concentrations of Bronsted acid sites react stoichiometrically with these sites, yielding diarylalkanes. At low concentrations, the Bronsted acid sites can act catalytically resulting in isomerization reactions.
- Kao, Hsien-Ming,Grey, Clare P.,Pitchumani, Kasi,Lakshminarasimhan,Ramamurthy
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p. 5627 - 5638
(2007/10/03)
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- Formation and rearrangement of gem-dilithiodiphenylethene
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1,1-Dilithio-2,2-diphenylethene (14) is accessible through double bromine lithium exchange reaction starting from 1,1-dibromo-2,2-diphenylethene (5) with lithium metal at -110°C. 14 undergoes rearrangement into (E)-1-lithio-2-(2-lithiophenyl)-2-phenylethene (13) at temperatures above -100°C. The (Z)-compound 15 was formed from the (E)-compound 13 at temperatures above -25°C.
- Maercker, Adalbert,Boes, Benno,Hajgholipour, Mohammad Taghi
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p. 143 - 149
(2007/10/03)
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- Reactivity and Selectivity in the Oxidation of Styrene Derivatives. IV. Studies on the Oxidation of Substituted β,β-Dimethylstyrenes
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The liquid phase oxidation of substituted (p-MeO-, p-Cl-, m-CF3-) 2-aryl-3-methyl-but-2-enes, of 1,1-diphenyl-2-methyl-propene, of 1-ethoxy-2-methyl-1-phenyl-propene and of 9-isopropylidene-fluorene with pure oxygen was investigated in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 65-125°C. The product yields were determined gaschromatographically. The differences of the activation energies of epoxide formation and the parallel reactions were calculated. They amount to 19-48 kJ/mol. The epoxide selectivity increases with increasing temperature and increasing concentration of olefin. The relative chain propagation constants (kpC=C) were determined by competitive oxidation with cumene. The kpC=C values of substituted β,β-dimethylstyrenes can be correlated by a LFE-relationship with the ionisation energies of the olefins.
- Suprun
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p. 247 - 255
(2007/10/03)
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- Photochemistry of Organic Molecules Entwined in Spiderwebs; The Use of Poly(methyl methacrylate) Glass for Restricting Excited-State Motion
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A study of several unimolecular photochemical rearrangements in poly(methyl methacrylate) glass was carried out with the intent of comparing the behavior of excited-state species trapped in a polymer matrix with both the corresponding solution photochemistry and that in crystal lattices.Three reactants were studied: (a) 4,5,5-triphenylcyclohex-2-en-1-one, (b) 1,1-dicyano-3,3,5,5-tetraphenyl-1,4-pentadiene, and (c) 2,2-dimethyl-1,1-diphenyl-3-(2,2-diphenylvinyl)cyclopropane.The solution photochemistry of the three compounds had previously been studied in our laboratory, and the photochemistry in the crystal lattice had been similarly investigated for the first two.The crystal lattice photochemistry of the last of the three was investigated in the present study.For each of the three reactants, different photochemical behavior was observed depending on the environment-polymer glass, solution, or crystal lattice.The experimental behavior correlated nicely with theoretical assessment of molecular motion of the component atoms in proceeding onward from that point along the reaction coordinate where multiple reaction pathways are available.The preferred reaction pathway proved consistently to require the least motion and the minimum molecular volume displacement.A concept of least motion dependent on its application to the "branch point" rather than the entire conversion of reactant to product was established.
- Zimmerman, Howard E.,O'Brien, Michael E.
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p. 1809 - 1816
(2007/10/02)
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- Interaction of Heterocyclic Nitrones With Organometallic Reagents As a Method For the Synthesis of New Types of Nitroxides
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The reactions of heterocyclic nitroxides: 3-imidazoline-3-oxides, 2H- (4H)-imidazole mono- and dioxides, dihydropyrazine-1,4-dioxides, with organometallic reagents and subsequent oxidation led to heterocyclic nitroxides of 3-(2)-imidazoline and 3-(2)-imidazoline-3-oxide, dihydropyrazine oxide, monocyclic imidazolidine biradicals and stable acyclic nitroxides with hydrogen at the α-carbon atom.
- Reznikov, Vladimir A.,Volodarsky, Leonid B.
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p. 10669 - 10692
(2007/10/02)
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- Reaction of Chiral Cyclopropyl Halides with SmI2
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Reductions of (S)-(+)-1-bromo-1-methyl-2,2-diphenylcyclopropane (7), (S)-(+)-1-bromo-1-(methoxymethyl)-2,2-diphenylcyclopropane (19), and (R)-(-)-1-fluoro-1-iodo-2,2-diphenylcyclopropane (11) with samarium(II) iodide is reported.Evidence for a samarium(III) intermediate in the reaction is presented.
- Walborsky, H. M.,Topolski, Marek
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p. 370 - 373
(2007/10/02)
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- A Ketyl Radical Probe Experiment. The Reactions of o-Halobenzophenones with Various Wittig Reagents
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The ketyl radical probe experiments of o-, m-, or p-bromobenzophenone and iodobenzophenone with nonstabilized, semistabilized, and stabilized ylides in THF and THF suggested the presence of radical anion species of sufficient lifetime in the reaction with a nonstabilized ylide.
- Yamataka, Hiroshi,Ando, Katsuhiro,Takatsuka, Tsutomu,Hanafusa, Terukiyo
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p. 1531 - 1534
(2007/10/02)
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- Thermal Decomposition of 3,3,5-Trisubstituted-4,4-dimethyl-4,5-dihydro-5-hydroperoxy-3H-pyrazoles: Route to β,γ-Unsaturated Ketones
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The thermal decomposition of a series of cyclic α-azo hydroperoxides (3,3,5-R1, R2, R3-4,4-dimethyl-4,5-dihydro-5-hydroperoxy-3H-pyrazoles; 2a R1 = R2 = R3 = Ph; 2b R1= R3 = Ph, R2 = Me; 2c R1 = R3 = p-Anisyl, R2 = Me; 2d R1 = R2 = Me, R3 = Ph; 2e R1 = R3 = Me, R2 = Ph), synthesized by oxidation of the corresponding 3,4-dihydro-2H-pyrazoles, proceeded smoothly with evolution of nitrogen.The relative stability series was found to be 2a > 2c ca. 2b > 2d > 2e.For 2a, the products were 1,4,4-triphenyl-2,2-dimethylpropanone and 1,1-dimethyl-2,2-diphenylethylene.For 2b-e,m β,γ-unsaturated ketones were obtained as the major products in ca. 60percent yield from the thermolyses.The products are consistent with a free-radical mechanism involving initial homolysis of the O-O bond followed by loss of nitrogen to yield a free-radical beta to the carbonyl group.For 2a, β-scission and hydrogen-atom abstraction of the hydroperoxy proton by the β-keto radical (induced decomposition) are the major pathways leading to products.For 2b-c, abstraction of a γ-hydrogen atom of the β-keto radicals by hydroxy radical accounts for the formation of the β,γ-unsaturated compounds as the major product.
- Baumstark, Alfons L.,Vasquez, Pedro C.
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p. 113 - 117
(2007/10/02)
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- Nickel-Catalyzed Olefination of Cyclic Benzylic Dithioacetals by Grignard Reagents. Scope and Mechanism
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The details of the first nickel-catalyzed olefination of cyclic dithioacetals to form substituted styrenes and aryl-substituted 1,4-pentadienes are described.The reaction represents a new synthetic use of the dithioacetal functionality.Only nickel complexes catalyzes these cross-coupling reactions; palladium complexes displayed no catalytic activity under the reaction conditions employed.Selective coupling occurred.A mechanism for the reaction is proposed.The experimental evidence indicates that, in these nickel-catalyzed couplings, cyclic dithioacetals are more reactive than their acyclic analogues.This increased reactivity appears to be the result of maintaining the two sulfur atoms in close proximity to each other by the use of a short chain of methylene groups.
- Ni, Zhi-Jie,Mei, Nai-Wen,Shi, Xian,Tzeng, Yih-Ling,Wang, Maw Cherng,Luh, Tien-Yau
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p. 4035 - 4042
(2007/10/02)
-
- An esr study of aromatic olefin radical cations
-
γ-Irradiation of phenyl-and diphenylethenes in CFCl3 matrix at 77 K resulted in the formation of the substrate radical cations. 1,1-Diphenyl-2-methylpropene radical cations exhibit a spin density (ρ=0.45) at the β carbon much higher than those of stilbene and 2-styrylnaphthalene radical cations and comparable to those of styrene and α-methylstyrene radical cations. The spin density at the vinyl carbons appears to play an important role in governing the reactivity of the olefin radical cations with molecular oxygen.
- Bonazzola,Michaut,Roncin,Misawa,Sakuragi,Tokumaru
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p. 347 - 352
(2007/10/02)
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- Organic Photochemical Reactions. XXXII. Photochemical Ring-Cleavage Reactions of 2,2-Diaryloxetanes in the Presence of Electron Donor
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Photochemical ring-cleavage reactions of 2,2-diaryloxetanes in the presence of triethylamine gave 1,1-diarylethenes selectively.
- Nakabayashi, Kenichi,Fujimura, Shin,Yasuda, Masahide,Shima, Kensuke
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p. 2733 - 2735
(2007/10/02)
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- An Assortment of Highly Unusual Rearrangements in the Photochemistry of Vinylcyclopropanes. Mechanistic and Exploratory Organic Photochemistry
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The singlet and triplet photochemistry of 2,2-dimethyl-1,1-diphenyl-3-(2,2-diphenylvinyl)cyclopropane and 3-(2,2-dicyanovinyl)-2,2-dimethyl-1,1-diphenylcyclopropane was investigated.In the (diphenylvinyl)cyclopropane case, direct irradiation led via the s
- Zimmerman, Howard E.,Oaks, Frank L.,Campos, Pedro
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p. 1007 - 1018
(2007/10/02)
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- Rhodium-catalyzed C-C coupling reactions involving ring opening of strained molecules. II. Addition to olefins and aromatic substitution
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Rhodium-catalyzed C-C coupling reactions, involving ring opening of strained molecules, have been studied using diphenylmethylenecyclopropanes as models.It has been established that, as rhodium takes control of the ring opening process, activated olefins
- Chiusoli, Gian Paolo,Costa, Mirco,Melli, Luca
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p. 495 - 506
(2007/10/02)
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- The Aryl Version of the Cyclopropyl-?-Methane Rearrangement. Partitioning of a 1,4-Diradical: Mechanistic and Exploratory Organic Photochemistry
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The photochemistry of 2-(2,2-diphenylcyclopropyl)-2-phenylpropane (8) was investigated in a search for the arylcyclopropylmethane counterpart of the known vinylcyclopropylmethane reaction.Direct irradiation of arylcyclopropylmethane 8 led to 1,1-diphenylethylene (3) and 1-phenyl-2-methyl-1-propene (13) as products in addition to the usual Griffin fragmentation leading to diphenylcarbene (15) and 3-methyl-3-phenyl-1-butene (7). 1,1,3-Triphenyl-2,2-dimethylcyclobutane (12) was considered as a potential reaction intermediate.The cyclobutane was synthesized and found to afford alkenes 3 and 13 on irradiation.However, dynamic isotope dilution revealed that only 1percent of the reaction did proceed via this intermediate, and its presence was eventually detected by FT NMR.The triplet of arylcyclopropane 8 proved unreactive.A third mechanism involving a Griffin fragmentation was considered and ruled out by independent generation of the carbene and observation of the products.Quantum yields were obtained.Also excited singlet-state lifetimes and reaction rates were determined by using single photon counting.The electronic features leading to the observed reactivities are discussed.
- Zimmerman, Howard E.,Carpenter, Clint W.
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p. 3298 - 3305
(2007/10/02)
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- Novel Coupling of Dithioacetals with Grignard Reagents
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Dithioacetals react with Grignard reagents in the presence of a catalytic amount of to give the corresponding olefinic coupling products in good yields: a mechanism for the reaction is suggested.
- Ni, Zhi-Jie,Luh, Tien-Yau
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p. 1515 - 1517
(2007/10/02)
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- Reactions of Triplet Carbenes with Sulfides and Disulfides: Ylide vs. Radical Formation
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The reactions between triplet diphenylcarbene and fluorenylidene with a variety of sulfides and disulfides were investigated with use of electron paramagnetic resonance (EPR) spectroscopy, laser flash photolysis, and product studies.Diphenylcarbene reacted with these substrates by a radical-like displacement mechanism.Rate constants were ca. 1E6 M-1 s-1, and the resulting thio-substituted diphenylmethyl radicals were identified by their EPR and optical spectra.By contrast, the analogous reactions of fluorenylidene had rate constants of 1E8-1E9 M-1 s-1 and proceeded by an ylide mechanism.Product studies were consistent with these results but were not sufficient in themselves to reveal these mechanistic differences.
- Alberti, A.,Griller, D.,Nazran, A. S.,Pedulli, G. F.
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p. 3024 - 3028
(2007/10/02)
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- AN INTERPRETATION OF THE SUBSTITUENT EFFECT IN THE BLAISE REARRANGEMENT IN TERMS OF PI-ORBITALS
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The migratory aptitude of the substituent groups in the Blaise rearrangement can be explained in terms of the pi-electronic properties of the groups in the highest occupied molecular orbitals.The rates of the rearrangement reaction with relation to the substituent groups were also rationally understood based on the energy levels of the molecular orbitals.
- Abe, Yukio,Suehiro, Tadashi
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p. 389 - 392
(2007/10/02)
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- THE DIMER OF 2-METHYL-1,1-DIPHENYLPROPYL RADICALS AND ITS REACTIVITY
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The title radicals dimerize to an α,p-dimer 2 and not to an α,α-dimer 3 as previously assumed.The structure of the dimers of t-benzhydryl radicals Ph2CR in general is strongly dependent on the bulkiness of the R group.
- Beckhaus, Hans-Dieter,Schaetzer, Juergen,Ruechardt, Christoph
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p. 3307 - 3310
(2007/10/02)
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- Vinylation of Aromatic Substrates with Solvolytically Generated Trisubstituted Vinyl Cations
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Vinylation of aromatic compounds by α-aryl-β,β-disubstituted vinyl bromides (3a-i) in the presence of silver salts and 2,6-lutidine or 2,6-di-tert-butyl-4-methylpyridine proceed with high yields.The silver triflate assisted reaction is preferable to the silver tetrafluoroborate assisted reaction.The reaction of 1-anisyl-2,2-diphenylvinyl bromide gives a ρ+ value of -4.08 and high intramolecular selectivity with ko/kp ratios of 6.2-78.It is suggested that the reaction proceeds via intermediate α-arylvinyl cations and that the inter- and intramolecular selectivities are determined in the same transition state.
- Kitamura, Tsugio,Kobayashi, Shinjiro,Taniguchi, Hiroshi,Rappoport, Zvi
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p. 5003 - 5009
(2007/10/02)
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- Unusual Solvent Effects in the Wittig Reaction of Some Ketones Indicating Initial One-Electron Transfer
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Investigation of the Wittig reaction of adamantanone, 1, and some other ketones in various solvent systems with alkylidenetriphenylphosphoranes indicates an initial one-electron transfer from the ylide to the carbonyl group.In hydrogen-donor solvents, the hydrogen abstraction from the solvents by the radical ions generated by the one-electron transfer competes considerably with the olefin-forming Wittig reaction, giving unexpected reduction of the carbonyl group.It is shown that such reductions become the major pathway when steric hindrance affects the usual olefin-forming Wittig reaction.
- Olah, George A.,Krishnamurthy, V.V.
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p. 3987 - 3990
(2007/10/02)
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- RADIKALISCHE REAKTIONSWEGE BEI THERMISCH INDUZIERTEN UMSETZUNGEN VON ZIRCONOCENKOMPLEXEN
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The formation of products 2, 3 and 4(a-l) from both the reaction of εta2-bezophenone zirconocene 1 with alkyl halides and the thermolysis of the α-(Cp2ZrCl)-substituted benzhydrylmethylether 9, the latter proceeding with anchimeric assistance of the metal, can be understood assuming a stepwise reaction path through radical intermediates.The proposed intermediate transition-metal benzophenone ketyl 12 exhibits a reaction pattern differing from analogous main-group-metal ketyls.
- Erker, G.,Rosenfeldt, F.
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p. 1285 - 1292
(2007/10/02)
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- Thermal fragmentation of 3-alkyl-2-phenyloxetanes, 3,3-dimethyl-2-aryloxetanes, and related compounds. A case study of 2-aryl-substituted oxetanes
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Thermolyses of epimeric 3-alkyl-2-phenyloxetanes (1c, 1t, 2c, 2t, 3c, and 3t), 3,3-dimethyl-2-aryloxetanes (4, 5, 6, 7, and 8), 3,3,4,4-tetramethyl-2,2-diphenyloxetane (9), and 3,3-dimethyl-2,2-diphenyloxetane (10) were studied in degassed N,N,N',N'-tetramethylethylenediamine at 270-350 deg C.Although the fragmentation of 9 and 10 can be understandable on the basis of a diradical mechanism, there were several observations, in the reaction of certain other oxetanes, which could hardly be explained simply in terms of such a mechanism.Namely, (1) less strained 1t reacted faster than more strained 1c; (2) a major mode of the fragmentation for 1c, 2c, and 3c was "B" (forming an alkene and benzaldehyde), whereas that for 1t, 2t, and 3t was "A" (forming an alkenylbenzene and formaldehyde); (3) the apparent energy of activation for the "B" process seemed to be larger than that for the "A"; (4) a dramatic change of the major fragmentation mode from "B" to "A" was brought about by a substituent on the phenyl group, as was observed in 4-8.These results may be explained reasonably by assuming that the fragmentation proceeds, at least, in dual reaction courses.In competition with an anticipated diradical pathway, there will be another process, which is energetically little more favorable than the diradical fragmentation, rather specific to the "A" mode fragmentation, and important particularly in the reaction of the trans isomers.Probable candidates for the second process are discussed.
- Imai, Toshiro,Nishida, Shinya
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p. 2503 - 2509
(2007/10/02)
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- CONCERTED FRAGMENTATION CONCURRENT WITH A STEPWISE-DIRADICAL FISSION IN THE OXETANE THERMOANALYSIS; IMPORTANCE OF STERIC STRAIN
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Thermolytic behavior of 3-alkyl-2-phenyloxetanes, in particular that of trans isomers, is best explained by concurrent concerted fragmentation and stepwise diradical fission.Proportion of the concerted process should be small in the cis isomers because of destabilization of the transition state by steric strain.The argument is supported by the thermal behavior of 3-alkyl-4-phenyl-oxetanones.
- Imai, Toshiro,Nishida, Shinya
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