- Metal-Free [2 + 1 + 2]-Cycloaddition of Tosylhydrazones with Hexahydro-1,3,5-triazines to Form Imidazolidines
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A novel protocol toward imidazolidines has been accomplished using tosylhydrazones and hexahydro-1,3,5-triazines as the substrates under metal-free reaction conditions. Importantly, the role of LiOtBu has been confirmed not only to release the diazo but also to promote the cycloaddition. Further mechanistic investigations reveal that the reaction proceeds through a stepwise [2 + 1 + 2] process.
- Liu, Pei,Xu, Guangyang,Sun, Jiangtao
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Read Online
- Medium-dependent Trapping of Diazoalkane Intermediates During Photolysis of Diazirines
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Photolysis of an intimate mixture of methyl(phenyl)diazirine and N-methylmaleimide in the absence of solvent permits the diazoalkane intermediate to be trapped, whereas the equivalent reaction in solution gives only cyclopropanated adducts.
- Bennett, Peter,Harwood, Laurence M.,Macro, Jason,McGregor, Andrew
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Read Online
- Reactive separation of β-bromoethylbenzene from α-β-bromoethylbenzene mixtures: a Zn2+-mediated radical polymerization mechanism
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A Zn2+-induced reactive separation method for the purification of β-bromoethylbenzene from α-β-bromoethylbenzene mixtures is discovered, where the selective decomposition of α-bromoethylbenzene follows a radical mechanism. Zn2+ facilitates the homolysis of the C-Br bond of halohydrocarbons with benzyl bromide, enabling the separation of the corresponding isomers with almost identical physical properties.
- Deng, Tianyu,Tian, Jiaming,Yan, Binhang,Zhu, Junqiu
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p. 1219 - 1222
(2022/02/03)
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- Triphosgene and DMAP as Mild Reagents for Chemoselective Dehydration of Tertiary Alcohols
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The utility of triphosgene and DMAP as mild reagents for chemoselective dehydration of tertiary alcohols is reported. Performed in dichloromethane at room temperature, this reaction is readily tolerated by a broad scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is generally favored, a dramatic change in alkene selectivity toward the Zaitzev products is observed when the reaction is carried out in dichloroethane at reflux.
- Ganiu, Moshood O.,Cleveland, Alexander H.,Paul, Jarrod L.,Kartika, Rendy
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p. 5611 - 5615
(2019/08/01)
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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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- An unprecedented approach to the Gabriel amine synthesis utilizing tosylhydrazones as alkylating agents
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A new and one-pot version of the Gabriel phthalimide amine synthesis utilizing carbonyl compounds as alkylating agents via their tosylhydrazone surrogates is disclosed. The alkylation involves copper catalysed carbene insertion into the N-H bond of phthalimide. Basically, the protocol also offers a powerful tool for deoxygenative hydroamination of carbonyl compounds.
- Yadav, Arvind K.,Yadav, Lal Dhar S.
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p. 34764 - 34767
(2014/11/08)
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- B12-TiO2 Hybrid Catalyst for Light-Driven Hydrogen Production and Hydrogenation of C-C Multiple Bonds
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The B12-TiO2 hybrid catalyst mediates H2O reduction to form hydrogen under UV irradiation (turnover number of one per hour). The catalyst also mediates reductions of alkenes such as styrene derivatives and alkylacrylates (maximum turnover number of 100 per hour) under mild conditions of room temperature, ordinary pressure, and water or alcohol as solvent.
- Shimakoshi, Hisashi,Hisaeda, Yoshio
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p. 1250 - 1253
(2016/02/18)
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- An easy access to fluoroalkanes by deoxygenative hydrofluorination of carbonyl compounds via their tosylhydrazones
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An efficient and operationally simple synthesis of fluoroalkanes by deoxygenative hydrofluorination of carbonyl compounds via their tosylhydrazone surrogates is reported. The reaction can be carried out in a one-pot procedure directly from carbonyl compounds.
- Yadav, Arvind K.,Srivastava, Vishnu P.,Yadav, Lal Dhar S.
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p. 2154 - 2156
(2013/03/14)
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- Quest for diatomic selenium
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Metallocene pentaselenides and elemental selenium were employed in an effort to generate diatomic selenium (Se2) under thermal conditions. Trapping experiments were carried out with six dienes. A successful formation of a diselenium adduct was observed in the case of 5,6-dimethylene-cyclohexa-1,3- diene (1a). The other dienes produced the corresponding dihydroselenophenes. The in-depth study of the limitations of our method to generate Se2 is described; a plausible mechanism rationalizing the observed results is proposed.
- Rys, Andrzej Z.,Schultz, Erwin K. V.,Harpp, David N.
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experimental part
p. 351 - 371
(2011/01/12)
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- Insights into the general and efficient cross McMurry reactions between ketones
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The selective cross McMurry couplings of diaryl or aryl ketones with various substituted ketones were achieved in 53-94% isolated yields. It is believed that the strong affinity of the substituents to the low-valent titanium surface plays an important role in regards to moderating selectivity. Through the introduction of such substituents followed by their removal post McMurry coupling, structurally similar ketones can be effectively cross-coupled.
- Duan, Xin-Fang,Zeng, Jing,Lue, Jia-Wei,Zhang, Zhan-Bin
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p. 9873 - 9876
(2007/10/03)
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- Reaction of ketone hydrazones with diselenium dihalides: Simple synthesis of Δ3-1,3,4-selenadiazolines and 2,5-diarylselenophenes
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Sterically congested cis- and trans-Δ3-1,3,4- selenadiazolines were isolated by one-pot reactions of ketone hydrazones with diselenium dibromide, which suggested the in situ formation of selone and diazoalkane intermediates. The thermolysis of these compounds gave symmetrical olefins, whereas oxidation afforded the corresponding azines. The reaction of acetophenone hydrazones with diselenium dibromide afforded 2,5- diarylselenophenes in moderate yields. The reaction proceeded through selone intermediates.
- Okuma, Kentaro,Izaki, Toshiharu,Kubo, Kento,Shioji, Kosei,Yokomori, Yoshinobu
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p. 1121 - 1126
(2007/10/03)
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- Stereoselective hydrogenations of aryl-substituted dienes
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The carbene complex 1 can mediate hydrogenations of dienes with up to 20:1.0 diastereoselectivity and 99% ee; the scope and limitations of these reactions were investigated. The Royal Society of Chemistry 2005.
- Cui, Xiuhua,Ogle, James W.,Burgess, Kevin
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p. 672 - 674
(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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- 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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- New desulfurdimerization of dithioketals induced by a 2,2'-bipyridine ligated nickel(0) complex
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Desulfurdimerization of various aromatic dithioketals is efficiently induced by a 2,2'-bipyridine ligated nickel(0) complex under mild conditions.
- Lourak, Moushine,Becker, Sandrine,Fort, Yves,Caubere, Paul
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- Low-valent titanium mediated reductive cleavage of benzylidene acetals: A modified McMurry reaction
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Reductive cleavage of benzylidene acetals using low-valent titanium reagent results in the formation of aryl alkanes and stilbenes. Aliphatic acetals, however, remain unaffected. This cleavage offers an attractive, alternate stereoselective route to stilbenes in a modified McMurry reaction.
- Talukdar, Sanjay,Nayak, Sandip K.,Banerji, Asoke
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p. 2325 - 2335
(2007/10/03)
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- Synthesis of dialkenyl dichalcogenides via alkenechalcogenolate ions generated by treating ketone p-Toluenesulfonylhydrazones with a base and elemental chalcogen
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Alkeneselenolate and alkenetellurolate ions were generated by treating ketone p-toluenesulfonylhydrazones possessing an α-methylene or an α-methine group with t-BuOK and elemental selenium or tellurium, respectively, at 110-150°C, and were converted into dialkenyl dichalcogenides by aerobic oxidation.
- Shimada, Kazuaki,Asahida, Mitsuharu,Takahashi, Ken,Sato, Yoshitaka,Aoyagi, Shigenobu,Takikawa, Yuji,Kabuto, Chizuko
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p. 513 - 514
(2007/10/03)
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- Influence of external ligands and auxiliaries on the reactivity of low-valent titanium in McMurry reaction: Selectivity and mechanistic profile
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Influence of various external ligands/auxiliaries on the reductive carbonyl coupling reactions mediated by low-valent titanium (LVT) reagents (McMurry coupling) has been explored. The LVT species generated from Tyrlik's TiCl3-Mg-THF system has been selected for the reactivity-tuning trials. Our studies show that incorporation of about 10 equiv of pyridine (a π-acceptor ligand) with respect to TiCl3 to the THF solvated LVT reagent could arrest the reductive dimerization of acetophenone at the intermediate pinacol stage. Modulation of the LVT-species by covalently-binding monohydroxy, 1,2- and 1,3-dihydroxy auxiliaries also resisted deoxygenation completely to give the pinacols in higher yields and better diastereoselectivity, as compared to pyridine-modified LVT system. Amongst these modified reagents, the LVT-catechol (1:1) system was found to be the most efficient combination for total pinacolization of aromatic carbonyl compounds, even under refluxing conditions. The actual titanium reagent responsible for this transformation is proposed to be a Ti(II) complex formed in situ. Further enhancement of stereoselectivity (threo-selectivity) of the pinacols has been achieved by carrying out the reactions with LVT-complexes modified by a variety of covalently-linking auxiliaries at low temperatures. The results demonstrate that by the judicious incorporation of various ligands/auxiliaries into LVT reagents it is possible to widen the scope and applicability of the classical McMurry reaction.
- Balu,Nayak,Banerji
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p. 5932 - 5937
(2007/10/03)
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- Synthesis of α,α-disubstituted acetic acids using low-valent titanium
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Digalogenocarbenes generated using low-valent titanium (LVT) undergo a one-pot cycloaddition to diaryl, aryl alkyl or dialkyl ketones to give α,α-disubstituted acetic acids such as (R,S)-2-arylpropanoic acids.TiI4 proved most effective in this reaction for which the product yield was optimized by use of an excess of reducing agent.
- Garcia, Mariano,Campo, Carmen del,Llama, Emilio F.,Sinisterra, Jose V.
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p. 1771 - 1774
(2007/10/02)
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- Ketone Coupling on Reduced TiO2 (001) Surfaces: Evidence of Pinacol Formation
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Reductive coupling of acetone and acetophenone was investigated in temperature-programmed desorption (TPD) studies on both reduced (Ar(1+)-bombarded) and oxidized TiO2 (001) surfaces.The principal reaction product of either ketone on the reduced surface was a symmetric olefin with twice the carbon number of the reactant. 2,3-Diphenyl-2-butene comprised over 65percent of the volatile carbon-containing species desorbed from the reduced surface following acetophenone adsorption.The main side reactions which yielded products of the same carbon number as the reactants included deoxygenation to form olefins and deoxygenation plus hydrogenation to yield saturated species.The yield of reduction products was greatly diminished on the oxidized TiO2 (001) surface; the yield of 2,3-dimethyl-2-butene, the reductive coupling product of acetone, decreased 10-fold with respect to the yield from the reduced surface.This decrease in activity for reductive coupling is similar in scale to that observed for benzaldehyde coupling on the same surfaces, supporting the conclusion that both ketone and aldehyde coupling reactions occur at ensembles of Ti cations able to undergo a four-electron oxidation.Phenyl groups adjacent to the carbonyl carbon have the greatest effect on the carbonyl coupling reaction, giving significantly higher yield of the coupled olefin product.The observation of a small amount of the pinacol, 2,3-diphenyl-2,3-butanediol, during acetophenone TPD is the first direct evidence that the carbonyl coupling reaction on reduced TiO2 surfaces proceeds through a pinacolate intermediate, as it does for the McMurry reaction carried out in liquid-solid slurries.
- Pierce, Keith G.,Barteau, Mark A.
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p. 2405 - 2410
(2007/10/02)
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- Organomolybdenum and Organotungsten Reagents, VI. - On the Carbonyl-Methylenating Molybdenum-Aluminium and Tungsten-Aluminium μ-Methylene Complexes
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MoCl5, MoOCl3(THF)2, MoO2Cl2, (MeO)2MoCl3, (MeO)4MoCl, WOCl3(THF)2, and WOCl4 form carbonyl-methylenating complexes and 1-2 equiv. of CH4 by reacting with 2 equiv. of Me3Al.These thermolabile complexes are prepared in solution and differ in their properties (e.g. ability to transfer mostly more than 1 CH2 unit per Mo or W atom in carbonyl-olefinating processes; high sensitivity to water, no hydroxy ketone affinity) from the carbonyl-olefinating 1,3-dimetallacyclobutanes (M = Mo, W) and are believed to be mono- and bicyclic analogs (e.g. hypothic structures 3, 6-8) of the Tebbe reagent (1), containing Mo-μCH2-Al or W-μCH2-Al groups, respectively.Analogous complexes seem to be produced by treating MoOCl3(THF)2 with 2 Me2Zn or (MeO)2MoCl3 and (MeO)4MoCl with 2 MeMgBr in each case.Unlike the dimeric and, due to a Mo-Mo bond, diamagnetic Mo(V) derivatives (MeO)2MoCl3 and (MeO)4MoCl (according to 1H-NMR structure 9 or 10 and 11 or 12, respectively) the complexes obtained by the reactions (MeO)2MoCl3 + 2 Me3Al and (MeO)4MoCl + 2 Me3Al are paramagnetic, indicating the expected absence of a Mo-Mo bond.The 1H-NMR spectrum of the reaction mixture obtained by treating the Mo(VI) derivative MoO2Cl2 with 2 Me3Al in THF shows various signals for μ-CH2 groups, whereas signals of t-CH2 ligands are missing (t = terminal).In analogy to 1 the carbonyl-olefinating activity of the Mo-Al and W-Al reagents is activated by the addition of 2 equiv. of HMPA.Treatment of PhCOCH2NEt2 (19) with leads to carbonyl olefination with formation of 20 and also to α-methylation with formation of PhCOCH(Me)NEt2 (21), pointing to the intermediate formation of a t-CH2-Mo ligand. has found to be the best reagent for the carbonyl olefination of aldehydes, whereas was optimal for ketones.In 1:1 reactions both reagents normally give better yields than the Tebbe reagent.By applying and on ketones 16-18 an interesting neighbour group effect of electron donor atoms in the δ position to the keto group was observed. - Key Words: Carbonyl olefination / Molybdenum aluminium complexes, organo / Tungsten aluminium complexes, organo / Tebbe reagent / Aluminium, molybdenum and tungsten complexes
- Kauffmann, Thomas,Enk, Manfred,Fiegenbaum, Petra,Hansmersmann, Ursula,Kaschube, Wilfried,et al.
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p. 127 - 136
(2007/10/02)
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- Thermal cleavage of the 3,4 bond in a cyclobutane-1,2-dione
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Pyrolysis of trans-3,4-dimethyl-3,4-diphenylcyclobutane-1,2-dione results in an isomerization interpreted to involve formation of a dioxatetramethyleneethane biradical. This biradical would arise from a hitherto unprecedented 3,4 bond cleavage.
- Peterson,Carpenter
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p. 3219 - 3222
(2007/10/02)
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- Zinc-Promoted Reactions. 2. Ionic and Nonionic Pathways in the Reduction of Acetophenone and 2,2-Dimethyl-1-phenylpropan-1-one
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The Clemmensen reduction of acetophenone and related substrates (PhCHXCH3, X = Cl, OH, OAc) was investigated in anhyd AcOH and in the presence of LiCl, HCl, or TFA.Ethylbenzene, 1-acetoxy-1-phenylethane, 2,3-diphenyl-2,3-butanediol, and 2,3-diphenyl-2-butene were formed in yields strongly dependent on the experimental conditions.The formation of the hydrocarbon was favored in neat AcOH and in AcOH/HCl/LiCl.Ionic and nonionic pathways were recognized.In the presence of Cl-, the proposed mechanism involves the intermediacy of PhCH(CH3)Cl.The process may proceed via *- and the carbon radical PhC*(CH3)OZnX.The second SET may lead to a carbanion, quenched by the acid to give PhCH(CH3)OZnX, a precursor of PhCHXCH3 (X = OAc, Cl).Coupling reactions, involving different radical species, account for the formation of the dimeric compounds.In the reduction of 2,2-dimethyl-1-phenylpropan-1-one, the preponderance of addition reactions, mainly involving Cl-, can be explained by the difficult approach of zinc metal to the hindered carbonyl group.Only traces of neopentylbenzene were obtained, the main product being 2-methyl-3-phenyl-2-butene.The proposed mechanism requires that the first SET occurs on adduct PhCCl(OH)C(CH3)3 to produce 2,2-dimethyl-1-phenylpropan-1-ol, the precursor of the alkene.
- Luchetti, Luciana,Rosnati, Vittorio
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p. 6836 - 6839
(2007/10/02)
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- Unprecedented Reductive Dealkoxylation of Aryl Alkyl Ethers and Intramolecular C-C Coupling of 2,2'-Dialkoxystilbenes with Low Valent Titanium: One-pot Synthesis of Phenanthrenes
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Facile dealkoxylation of aryl alkyl ethers has been carried out using TiCl3-Li-THF (tetrahydrofuran), a novel one-pot synthesis of phenanthrenes from ortho-alkoxyaromatic aldehydes/ketones is described.
- Banerji, Asoke,Nayak, Sandip, K.
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p. 1432 - 1434
(2007/10/02)
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- Radical and Ionic Reactions of (Benzoylmethyl)mercurials
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Photolysis of PhCOCH2HgCl or (PhCOCH2)2Hg yields benzoylmethyl radicals which can be trapped by anions such as Me2C=NO2-, RC(CO2Et)2-, RC(O-)=CH2 or by other electron-rich systems such as (RO)3P, N-methylpyrrole, enamines, or norbornene.Electron transfer from the adduct radicals to the mercurials yields PhCOCH2A from the anions A-, PhCOCH2P(O)(OR)2 from P(OR)3, and the phenacyl derivative from N-methylpyrrole or enamines.Easily oxidized anions such as PhCOCPh2- or PhC(CH3)=NO2- react with PhCOCH2* by electron transfer to yield the dimer derived from the anion.Addition of PhCOCH2* to norbornene yields a substituted 3-benzoylpropyl radical which cyclizes at the ortho position of the benzoyl group to give the α-tetralone derivative.
- Russell, Glen A.,Kulkarni, Shekhar V.,Khanna, Rajive K.
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p. 1080 - 1086
(2007/10/02)
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- Oxidative addition of carbon-oxygen and carbon-nitrogen double bonds to WCl2(PMePh2)4. Synthesis of tungsten metallaoxirane and tungsten oxo- and imido-alkylidene complexes
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WCl2L4 (1, L = PMePh2) reacts rapidly with a variety of ketones and aldehydes to form bis(η2-ketone) or bis(η2-aldehyde) complexes WCl2(η2-O=CRR′)2L2 (2, 3)
- Bryan, Jeffrey C.,Mayer, James M.
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p. 2298 - 2308
(2007/10/02)
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- Solvent effects on the energetics of intermolecular charge-transfer reactions
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Picosecond absorption spectroscopy is used to examine the intermolecular electron-transfer reaction between the trans-stilbene radical cation and a series of olefin radical anions in polar solvents. Laser excitation of a ground-state complex between trans-stilbene and electron-deficient olefins selectively generates the contact ion pair within the time resolution of the experiment. By monitoring the time-dependent absorption of the trans-stilbene radical cation, the dynamics of electron back-transfer and ion-pair separation are studied. The rate of electron back-transfer is found to be temperature independent in the series of polar aprotic solvents over the temperature range from -8 °C to +80 °C. However, a linear correlation is observed between the charge-transfer rate and solvent polarity. With this result, the temperature data are interpreted in terms of solvent polarity effects on the activation energy for charge transfer. Once the rates are corrected for variation of solvent polarity, activation parameters are determined and the contributions of solvation and intramolecular modes to the reorganizational energy are evaluated. The dynamics of ion-pair separation are also briefly discussed.
- O'Driscoll, Erin,Simon, John D.,Peters, Kevin S.
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p. 7091 - 7098
(2007/10/02)
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- DIAZIRINES IN CARBENOID REACTIONS CATALYZED BY RHODIUM(II) CARBOXYLATES
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Diazo compounds formed by thermal or photolytic rearrangement of 3-alkyl-3-phenyl-diazirines in the presence of catalytic amounts of rhodium(II) perfluorobutyrate are effectively directed to metal carbenoid products with minimal competition from processes which are dominant when the diazo compound is used directly or when the diazirine is decomposed in the absence of the catalyst.
- Doyle, Michael P.,High, Kenneth G.,Oon, Su-Min,Osborn, Antonio K.
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p. 3049 - 3052
(2007/10/02)
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- Synthesis of 2,3-diaryl-1,4-diazolyl-2,3-epoxybutanes
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2,3-Diaryl-1,4-diazolyl-2,3-epoxybutanes have been prepared from dimethylstilbenes.An efficient although neglected synthesis of the required olefins has been recovered from the literature.The target compounds show moderate antifungal activity.
- Moreno-Manas, M.,Teixido, M.
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p. 1439 - 1441
(2007/10/02)
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- Diazomethane Radical Cations as a Dipolarophile in the Dimeric Olefin Formation from Diazo-compounds
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A novel cycloaddition mechanism involving diazomethane radical cations is proposed for the dimeric olefin formation by the one-electron oxidation of the diazo-compounds.The preference of cis-stilbene formation from phenyldiazomethane is understood by a secondary orbital interaction of phenyl groups on the cycloaddition step.
- Ishiguro, Katsuya,Sawaki, Yasuhiko,Iwamura, Hiizu
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p. 1853 - 1856
(2007/10/02)
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- Facile, high yield synthesis of 2,3-diphenyl-1,3-butadiene
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A high yield, four step synthesis process is disclosed for producing the omer, 2,3-diphenyl-1,3-butadiene, wherein in step 1 acetophenone pinacol is produced from the dimerization of acetophenone in 96% yield; in step 2 acetophenone pinacol is reacted with triethoxymethane and benzoic acid to produce 2,3-diphenyl-2-butene in about 88-96% yield. The 2,3-diphenyl-2-butene and N-bromosuccinimide (NBS) are reacted together in step 3 in an ultra violet reactor and in a CCl4 reaction solvent to produce in about 92% yield, the dibromo compound, 1,4-dibromo-2,3-diphenyl-2-butene. In step 4, 1,4-dibromo-2,3-diphenyl-2-butene is converted to the desired monomer in about 86% yield by reacting with NaI under refluxing conditions for about 90 minutes in a hot acetone solution. The monomer 2,3-diphenyl-1,3-butadiene is recovered in hexane, shaken (in the order listed) with water solutions of NaHSO3, NaHCO3, and pure water, dried over CaCl2, and the hexane is spun off. The residue is then recrystallized from hot methyl alcohol by the addition of water. The crystals which are air dried should be refrigerated as soon as possible to prevent spontaneous polymerization.
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- REACTIONS OF Cp2Ti(CO)2 WITH ALDEHYDES AND KETONES
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Aromatic aldehydes are coupled by Cp2Ti(CO)2 to give pinacols and olefins in good yields.Aliphatic aldehydes react to give mainly the corresponding alcohols.Aromatic ketones give a mixture of products.
- Chen, T. L.,Chan, T. H.,Shaver, Alan
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- Molecular Rearrangements: Part XIII-Thermal Rearrangement of N-(α-Phenethyl)aniline and N-(β-Phenethyl)aniline
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Thermolysis of N-(α-phenethyl)-(I)- and N-(β-phenethyl)-(II)-anilines for ca. 7 days in the absence of promotors, results in the migration of phenethyl group to the aniline nucleus.Thermal rearrangement of II produces ethylbenzene, 1,4-diphenylbutane, 2,3-diphenylbutane, 2-phenylindole, aniline and 2- and 4-(α-phenethyl)anilines.A similar thermal rearrangement of I results in the same neutral products together with 2,3-diphenyl-2-butene.Thermolysis of I and II in the presence of isoquinoline affords, in addition to the above products, 1-(α-phenethyl)-isoquinoline.In the presence of β-naphthol, besides the normal products, 2,2'-dinapthol is obtained together with some heterocyclic compounds of unknown nature.The results have been interpreted in terms of a free radical mechanism.
- Badr, M. Z. A.,Abdel-Rahman, A.E.,El-Sherief, H. A. H.,Aly, M. M.
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p. 422 - 424
(2007/10/02)
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- Mechanism, regiochemistry, and stereochemistry of the insertion reaction of alkynes with methyl(2,4-pentanedionato)(triphenylphosphine)nickel. A cis insertion that leads to trans kinetic products
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This study reports the rapid reaction under mild conditions of internal and terminal alkynes with methyl(2,4-pentanedionato)(triphenylphosphine)nickel (1) in aromatic and ethereal solvents. In all cases vinylnickel products (2) are formed by insertion of the alkyne into the nickel-methyl bond. The regiochemistry is unusual; unsymmetrical alkynes give selectively the one regioisomer with the sterically largest substituent next to the nickel atom. So that the stereochemistry of the initial insertion could be investigated, an X-ray diffraction study of the reaction of 1 and diphenylacetylene was carried out. This showed that the vinylnickel complex formed by overall trans insertion was the product of the reaction. Furthermore, subsequent slow isomerization of this complex, to a mixture of it and the corresponding cis isomer, demonstrated that this trans addition product is the kinetic product of the reaction. In studies with other alkynes, the product of trans addition was not always exclusively (or even predominantly) formed, but the ratio of the stereoisomers formed kinetically was substantially different from the thermodynamic ratio. Isotope labeling, added phosphine, and other experiments have allowed us to conclude that the mechanism of this reaction does involve cis addition. However, a coordinatively unsaturated vinylnickel intermediate is initially formed, which can undergo rapid, phosphine-catalyzed cis-trans isomerization in competition with its conversion to the isolable phosphine-substituted products.
- Huggins, John M.,Bergman, Robert G.
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p. 3002 - 3011
(2007/10/02)
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- UNUSUAL REDUCTIVE CONDENSATIONS IN THE REACTION OF DIIODODIMETHYLSILANE WITH KETONES
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Diiododimethylsilane reacts with various ketones in the presence of zinc to give the corresponding reductive condensation products in good yields.
- Ando, Wataru,Ikeno, Masayuki
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p. 1255 - 1256
(2007/10/02)
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