- An unprecedented stereoselective titanium-mediated dihydrodimerization of allyl ethers and allylamines
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3-Phenylallyl ether 17, 2,5-dihydrofuran (1) and N-acceptor-substituted 2,5-dihydropyrrols 4, 6, 8, 10, 12 upon treatment with cyclohexylmagnesium bromide in the presence of Ti(Oi-Pr)4 were found to undergo a diastereoselective dihydrodimerization affording 1,5-dienes, d,1-2,3- diethenylbutane-1,4-diol (51% yield) and d,1-2,3-diethenyl-1,4- bis(sulfonylamino)butanes (43-52%), respectively. In the presence of titanium bis(4R,5R)-taddolate, the dihydrodimerization of 1 proceeded with 35-38% chemical yield and up to 94% ee.
- De Meijere, Armin,Stecker, Bj?rn,Kourdioukov, Alexandre,Williams, Craig M.
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Read Online
- A synthesis of allylboronates via the palladium(0)-catalyzed cross-coupling reaction of bis(pinacolato)diboron with allylic acetates
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The cross-coupling reaction of bis(pinacolato)diboron [(Me4C2O2)BB(O2C2Me4)] with allyl acetates regio- and E-stereoselectively provided the pinacol esters of allylboronic acids in high yields. The reaction was efficiently catalyzed by Pd[dba]2 in DMSO at 50°C.
- Ishiyama, Tatsuo,Ahiko, Taka-Aki,Miyaura, Norio
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Read Online
- Cobalt-Catalyzed Diastereo- And Enantioselective Reductive Allyl Additions to Aldehydes with Allylic Alcohol Derivatives via Allyl Radical Intermediates
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Catalytic generation of ambiphilic π-allyl-metal complexes and their utility in enantioselective transformations constitutes a powerful approach for introduction of allyl groups to a molecule. Herein an unprecedented cobalt-catalyzed highly site-, diastereo-, and enantioselective protocol for stereoselective formation of nucleophilic allyl-Co(II) complexes followed by addition to aldehydes is presented. The reaction features diastereo- and enantioconvergent conversion of easily accessible allylic alcohol derivatives to diversified enantioenriched homoallylic alcohols with a remarkably broad scope of allyl groups that can be introduced. Mechanistic studies indicated that allyl radical intermediates were involved in this process. These new discoveries establish a new strategy for development of enantioselective transformations through capture of radicals by chiral Co complexes, pushing forward the frontier of Co complexes for enantioselective catalysis.
- Wang, Lei,Wang, Lifan,Li, Mingxia,Chong, Qinglei,Meng, Fanke
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p. 12755 - 12765
(2021/08/30)
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- Palladium-Catalyzed Allyl-Allyl Reductive Coupling of Allylamines or Allylic Alcohols with H2as Sole Reductant
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Catalytic carbon-carbon bond formation building on reductive coupling is a powerful method for the preparation of organic compounds. The identification of environmentally benign reductants is key for establishing an efficient reductive coupling reaction. Herein an efficient strategy enabling H2 as the sole reductant for the palladium-catalyzed allyl-allyl reductive coupling reaction is described. A wide range of allylamines and allylic alcohols as well as allylic ethers proceed smoothly to deliver the C-C coupling products under 1 atm of H2. Kinetic studies suggested that the dinuclear palladium species was involved in the catalytic cycle.
- Zhou, Xibing,Zhang, Guoying,Huang, Renbin,Huang, Hanmin
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p. 365 - 369
(2021/01/26)
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- Nickel-Catalyzed Homo- And Cross-Coupling of Allyl Alcohols via Allyl Boronates
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A nickel-catalyzed homo- and cross-coupling of allylic alcohols to 1,5-dienes in the presence of B2pin2 with excellent regioselectivity has been developed. Mechanistic studies indicate that the reaction proceeds via sequential nickel-catalyzed borylation of allyl alcohols followed by cross-coupling of the resulting allyl boronates with allyl alcohols. The method was effectively applied to nickel-catalyzed allylation of aldehydes using allylic alcohols directly.
- Gan, Yi,Hu, Hui,Liu, Yuanhong
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supporting information
p. 4418 - 4423
(2020/06/27)
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- Cobalt-Catalyzed Csp3?Csp3Homocoupling
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An efficient and easy method for Csp3?Csp3homocoupling was developed using cobalt bromide as catalyst. A series of functionalized alkyl bromides and alkyl chlorides were coupled in high yields under mild conditions. This reaction seems to involve a radical intermediate. (Figure presented.).
- Cai, Yingxiao,Qian, Xin,Gosmini, Corinne
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supporting information
p. 2427 - 2430
(2016/08/16)
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- Copper-catalysed α-selective allylic alkylation of heteroaryllithium reagents
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2-Allyl-substituted thiophenes and furans are synthesised efficiently in a direct procedure using 2-heteroaryllithium reagents and allyl bromides and chlorides catalysed by ligand-free copper(i). The reactions take place under mild conditions, with excellent α-selectivity, high functional group tolerance and good yields for the SN2 products. This journal is
- Vila, Carlos,Hornillos, Valentn,Faans-Mastral, Martn,Feringa, Ben L.
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p. 9321 - 9323
(2014/12/11)
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- Single electron transfer-induced Grignard cross-coupling involving ion radicals as exclusive intermediates
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The mechanism of the previously developed cross-coupling reaction of aryl Grignard reagents with aryl halides was explored in more detail. Single electron transfer from an aryl Grignard reagent to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle consists entirely of anion radical intermediates.
- Uchiyama, Nanase,Shirakawa, Eiji,Hayashi, Tamio
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supporting information
p. 364 - 366
(2013/02/23)
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- Selective cross-coupling of organic halides with allylic acetates
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A general protocol for the coupling of haloarenes with a variety of allylic acetates is presented. Strengths of the method are a tolerance for electrophilic (ketone, aldehyde) and acidic (sulfonamide, trifluoroacetamide) substrates and the ability to couple with a variety of substituted allylic acetates. Secondary alkyl bromides can also be allylated under slightly modified conditions, demonstrating the generality of the approach. Finally, the coupling of a reactive vinyl halide could be achieved by the use of a very hindered ligand and more reactive, branched allylic acetates.
- Anka-Lufford, Lukiana L.,Prinsell, Michael R.,Weix, Daniel J.
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p. 9989 - 10000
(2013/01/15)
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- Nickel-catalyzed, sodium iodide-promoted reductive dimerization of alkyl halides, alkyl pseudohalides, and allylic acetates
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The first general method for the reductive dimerization of alkyl halides, alkyl mesylates, alkyl trifluoroacetates, and allylic acetates is reported which proceeds with low catalyst loading (0.5 to 5 mol%), generally high yields (80% ave yield), and good functional-group tolerance.
- Prinsell, Michael R.,Everson, Daniel A.,Weix, Daniel J.
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supporting information; experimental part
p. 5743 - 5745
(2010/09/18)
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- Mild TiIII- and Mn/ZrIV-catalytic reductive coupling of allylic halides: Efficient synthesis of symmetric terpenes
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(Chemical Equation Presented) Two new efficient methods for the regioselective homocoupling of allylic halides using either catalytic Ti III or the combination Mn/ZrIV catalyst have been developed. The regio- and stereoselectivity of the process proved to increase significantly when the Mn/ZrIV catalyst is used as the coupling reagent and when cyclic substituted allylic halides are used as substrates. The use of Lewis acids such as collidine hydrochloride allowed the quantity of catalyst to be lowered up to 0.05 equiv. We have proved the utility of these protocols with the synthesis of different terpenoids such as (+)-β-onoceradiene (1), (+)-β-onocerine (2), squalene (5), and advanced key-intermediates in the syntheses of (+)-cymbodiacetal (3) and dimeric ent-kauranoids as xindongnin M (4a).
- Barrero, Alejandro F.,Herrador, M. Mar,Quilez Del Moral, Jose F.,Arteaga, Pilar,Arteaga, Jesus F.,Dieguez, Horacio R.,Sanchez, Elena M.
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p. 2988 - 2995
(2007/10/03)
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- Manganese- or iron-catalyzed homocoupling of grignard reagents using atmospheric oxygen as an oxidant
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Atmospheric oxygen was used for the first time as an oxidant in metal-catalyzed homocoupling of Grignard reagents. These manganese- or iron-catalyzed reactions are efficient, cheap, and eco-friendly. They are applicable to the large-scale synthesis of symmetrical conjugated compounds. Copyright
- Cahiez, Gerard,Moyeux, Alban,Buendia, Julien,Duplais, Christophe
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p. 13788 - 13789
(2008/04/11)
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- Copper catalyzed oxidation of organozinc halides
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A wide range of organozinc substrates may be oxidized in the presence of catalytic copper to give carbon-carbon bonds in high yield. The Royal Society of Chemistry 2006.
- Su, Xianbin,Fox, David J.,Blackwell, David T.,Tanaka, Kiyotaka,Spring, David R.
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p. 3883 - 3885
(2007/10/03)
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- Synthesis of allylamides from allyl halides, carbon monoxide, and titanium-nitrogen complexes prepared from molecular nitrogen
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4-Phenylbut-3-enamide could be synthesized from corresponding 3-chloroprop-2-enylbenzene, carbon monoxide (1atm), and titanium-nitrogen complexes, prepared from Ti(OiPr)4, Li, TMSCl, and molecular nitrogen (1atm), using a palladium catalyst. The reaction proceeds via transmetalation of the titanium-nitrogen complex to an acylpalladium complex. PtBu3 as a ligand of the palladium catalyst, afforded a good result, and the amounts of Li and TMSCl affected the yield of amide. When the reaction was carried out using a bidentate ligand on the palladium complex under an atmosphere of argon instead of carbon monoxide, an allylamine derivative was obtained.
- Ueda, Kazutaka,Mori, Miwako
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p. 2907 - 2910
(2007/10/03)
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- A new cationic, chiral catalyst for highly enantioselective Diels-Alder reactions
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(Matrix presented) The Diels-Alder reaction of cyclopentadiene and 2-methacrolein is catalyzed by a chiral Lewis acid to form the exo adduct in 96% yield and 96% ee.
- Sprott, Kevin T.,Corey
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p. 2465 - 2467
(2007/10/03)
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- Trimethyl phosphite as a trap for alkoxy radicals formed from the ring opening of oxiranylcarbinyl radicals. Conversion to alkenes. Mechanistic applications to the study of C-C versus C-O ring cleavage
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Trimethyl phosphite, (MeO)3P, is introduced as an efficient and selective trap in oxiranylcarbinyl radical (2) systems, formed from haloepoxides 8-13 under thermal AIBN/n-Bu3SnH conditions at about 80 °C. Initially, the transformations of 8-13, in the absence of phosphite, to allyl alcohol 7 and/or vinyl ether 5 were measured quantitatively (Table 1). Structural variations in the intermediate oxiranylcarbinyl (2), allyloxy (3), and vinyloxycarbinyl (4) radicals involve influences of the thermodynamics and kinetics of the C-O (2 → 3, k1) and C-C (2 → 4, k2) radical scission processes and readily account for the changes in the amounts of product vinyl ether (5) and allyl alcohol (7) formed. Added (MeO)3P is inert to vinyloxycarbinyl radical 4 and selectively and rapidly traps allyloxy radical 3, diverting it to trimethyl phosphate and allyl radical 6. Allyl radicals (6) dimerize or are trapped by n-Bu3SnH to give alkenes, formed from haloepoxides 8, 9, and 13 in 69-95% yields. Intermediate vinyloxycarbinyl radicals (4), in the presence or absence of (MeO)3P, are trapped by n-Bu3SnH to give vinyl ethers (5). The concentrations of (MeO)3P and n-Bu3SnH were varied independently, and the amounts of phosphate, vinyl ether (5), and/or alkene from haloepoxides 10, 11, and 13 were carefully monitored. The results reflect readily understood influences of changes in the structures of radicals 2-4, particularly as they influence the C-O (k1) and C-C (k2) cleavages of intermediate oxiranylcarbinyl radical 2 and their reverse (k-1, k-2). Diversion by (MeO)3P of allyloxy radicals (3) from haloepoxides 11 and 12 fulfills a prior prediction that under conditions closer to kinetic control, products of C-O scission, not just those of C-C scission, may result. Thus, for oxiranylcarbinyl radicals from haloepoxides 11, 12, and 13, C-O scission (k1, 2 → 3) competes readily with C-C cleavage (k2, 2 → 4), even though C-C scission is favored thermodynamically.
- Ding, Bangwei,Bentrude, Wesley G.
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p. 3248 - 3259
(2007/10/03)
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- Cobalt-catalyzed heck-type reaction of alkyl halides with styrenes
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(Chemical Equqtion Presentation) A cobalt complex, CoCl2[1,6-bis(diphenylphosphino)hexane], catalyzes an alkylation reaction of styrenes in the presence of Me3SiCH2MgCl in ether to yield β-alkylstyrenes. A variety of alkyl halides including alkyl chlorides can be employed as an alkyl source. A radical mechanism is strongly suggested for this alkylation reaction. Copyright
- Ikeda, Yousuke,Nakamura, Tomoaki,Yorimitsu, Hideki,Oshima, Koichiro
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p. 6514 - 6515
(2007/10/03)
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- Integrated chemical process. Construction of highly substituted allylic moieties from allylic sulfones in one-pot
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According to 'integrated chemical process', a novel one-pot process for construction of highly substituted allylic moieties has been achieved. A series of alkylation of allylic sulfones and palladium-catalyzed reductive desulfonylation by use of LiBHEt3 is integrated. The double alkylation furnishes more substituted olefins. Use of arylzinc compounds in place of the hydride enables electrophilic alkylation/nucleophilic arylation in one-pot. The integrated process provides higher overall yields than the corresponding stepwise process.
- Orita, Akihiro,Watanabe, Akihiro,Tsuchiya, Hiroshi,Otera, Junzo
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p. 2889 - 2898
(2007/10/03)
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- Regio- and Stereoselective Synthesis of 1,5-Dienes Using Allylic Barium Reagents
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The highly α,α' selective and sterocontrolled homocoupling reaction of allylic halides was achieved using barium reagent.The double-bond geometry of the starting allylic chloride was completely retained.The α,α' cross-coupling products were also prepared stereospecifically and regioselectively by this method.
- Yanagisawa, Akira,Hibino, Hiroaki,Habaue, Shigeki,Hisada, Yoshiyuki,Yasue, Katsutaka,Yamamoto, Hisashi
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p. 1263 - 1268
(2007/10/03)
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- Zinc Mediated Allylation of Aldehydes and Ketones with Cinnamyl Chloride in Aqueous Medium
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The Zn mediated reactions of cinnamyl chloride with aldehydes and ketones in THF-NH4Cl(aq) give-besides α- and γ-addition products-phenyl propenes and dicinnamyls, indicating the presence of radical intermediates in the reaction.
- Sjoeholm, Rainer,Rairama, Riitta,Ahonen, Matthias
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p. 1217 - 1218
(2007/10/02)
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- Perturbation of the degenerate, concerted cope rearrangement by two phenyl groups in "active" positions of (E)-1,4-diphenylhexa-1,5-diene. Acceleration by high pressure as criterion of cyclic transition states
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Previous examinations of radical-stabilizing substituents in the two distinct types of position in the hypothetical "aromatic" transition state of the thermal Cope rearrangement, designated "a" or active and "n" or nodal after the allyl radical have concentrated on their effect in the "n" positions. In order to provide a quantitatively reliable reference for the "a" position, the activation parameters of the degenerate rearrangement of (6-13C)-1,4-diphenylhexa-1,5-diene have been evaluated: Ea = 30.8 ± 0.4 kcal/mol; log A = 10.14 ± 0.2. The soundly energetically-based proposition that these observations relate to a concerted mechanism is strongly supported by the observation of a 3.0-fold increase in rate of approach to equilibrium on increasing the pressure from 1 bar to 6000 bar (162°C; benzene-d6). This rearrangement like that of cis-1,2-divinylcyclobutane and rac- and meso-3,4-diphenylhexa-1,5-diene, has a negative volume of activation. In contrast, trans-1,2-divinylcyclobutane, which does not rearrange by a cyclic transition state and gives cycloocta-1,5-diene, 4-vinylcyclohexene, and butadiene as products, has a positive volume of activation. To place the possibility of reaction by the homolytic/colligative (dissociative/recombinative) mechanism on a "quantitative" base, a further sighting on the heat of formation of the cinnamyl radical is provided by activation parameters for thermal syn-anti equilibration between (E)- and (Z)-1,1′-bi-3-phenylcyclohex-2-enylidene: Ea = 35.8 ± 0.2 kcal/mol; log A = 12.7 ± 0.1. After correction for conjugative interaction between phenyl and the double bond in the educts and without regard for any proposed structure for the transition state, the two phenyl groups in "a" positions appear to have lowered the enthalpy of activation by 7.7 kcal/mol relative to the paradigm, hexa-1,5-diene, whereas the two phenyl groups in the "n" positions of 3,5-diphenylhexa-1,5-diene have lowered the enthalpy of activation by 17.0 kcal/mol.
- Doering,Birladeanu, Ludmila,Sarma, Keshab,Teles, Joaquim Henrique,Kl?rner,Gehrke, Jan-Stephan
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p. 4289 - 4297
(2007/10/02)
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- Synthesis and reaction of (η5-pentamethylcyclopentadienyl)bis(allyl)tantalum(III) complexes; crystal structure of Ta(η5-C5Me5)(η3-1-phenylallyl)2
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We report here the synthesis and X-ray structure of a mononuclear 16-electron (η5-pentamethylcyclopentadienyl)bis(allyl)-tantalum complex, Cp*Ta(η3-PhC3H4)2 (2).Carbonylation of 2 induced the coupling reaction with phenylallyl groups bound to tantalum to give 1,6-diphenyl-1,5-hexadiene and carbonyltantalum complexes.Oxidation of 2 with one-electron oxidants, DDQ and TCNQ, gave the tantalum(IV) complexes, *Ta(PhC3H4)2>.
- Mashima, Kazushi,Yamanaka, Yoshimichi,Gohro, Yoshihiko,Nakamura, Akira
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- On the Regioselectivity of Coupling of Substituted Allyl Radicals. Steric Versus FMO Control
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The photo-induced decomposition of substituted-homoallylic 4-nitrobenzenesulfenates produces substituted allyl radicals which undergo dimerization and coupling with the 4-nitrobenzenethiyl radical.The regioselectivity of the dimerization of the allyl redi
- Pasto, Daniel J.,L'Hermine, Gael
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p. 3259 - 3272
(2007/10/02)
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- AN IMPROVED METHOD FOR THE GENERATION OF ORGANOZINC CARBENOIDS AND ITS APLLICATION IN DICARBONYL COUPLING REACTIONS
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Reaction of aromatic aldehydes and certain α,β-unsatured carbonyl compounds with 1,2-bis(chlorodimethylsilyl)ethane and zinc leads to products of symmetrical dicarbonyl coupling. Key words: Dicarbonyl Coupling; 1,2-bis(chlorodimethylsilyl)ethane and Zinc
- Afonso, Carlos A. M.,Motherwell, William B.,O'Shea, Dennis M.,Roberts, Lee R.
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p. 3899 - 3902
(2007/10/02)
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- SINGLE-STEP PREPARATION OF ALLYLIC SULFIDES HAVING 1-PHENYLTETRAZOLE-5-THIO GROUP FROM ALLYLIC ALCOHOLS USING S,S'-BIS(1-PHENYL-1H-TETRAZOL-5-YL) DITHIOCARBONATE AND REACTIONS INVOLVING THE ALLYLIC SULFIDES
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The reaction of allylic alcohols and S,S'-bis(1-phenyl-1H-tetrazol-5-yl) dithiocarbonate (1) gave allylic sulfides having 1-phenyltetrazole-5-thio group in a single step.Furthermore, these allylic sulfides could be applied to carbon-carbon bond and carbon-sulfur bond formations by using Grignard reagents or carbanions in the presence of catalytic amount of copper(I) bromide or palladium (0), respectively.
- Takeda, Kazuyoshi,Tsuboyama, Kanoko,Torii, Katsumi,Murata, Maki,Ogura, Haruo
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p. 4105 - 4108
(2007/10/02)
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- REACTIONS OF ?-ALLYL COMPLEXES OF Ti(III) WITH ALLYL, ALKYL, AND PROPARGYL ELECTROPHILES
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The reactions of the ?-allyl complexes of Ti(III) with allyl bromides lead to the production of a mixture of cross-coupling and homocoupling products.In the case of alkyl and propargyl halides the dehalogenation products are formed.The reaction of the ?-allyl complexes of Ti(III) with allyl acetates, allyl phenyl ethers, and allyl aryl sulfones are catalyzed by Pd(PPh3)4 and give cross-coupling or elimination products, depending on the structure of the initial substrate.
- Kasatkin, A. N.,Kulak, A. N.,Tolstikov, G. A.,Lomakina, S. I.
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p. 1875 - 1889
(2007/10/02)
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- An Efficient Electrochemical Coupling of Allylic Halides by Using a Copper Anode
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A new electrolytic method for an efficient coupling of allylic halides by the use of a copper anode and a platinum cathode in the precence of sodium iodide is described.A method which avoids a loss of the copper anode owing to dissolution is also described.
- Tokuda, Masao,Endate, Kazuhiro,Suginome, Hiroshi
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p. 945 - 948
(2007/10/02)
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- Reaction of Phenyl-Substituted Allyllithiums with tert-Alkyl Bromides. Remarkable Difference in the Alkylation Regiochemistry between a Polar Process and the One Involving Single-Electron Transfer
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The reaction of phenyl-substituted allyllithiums 1a-h with tert-alkyl bromides was investigated systematically.The alkylation regiochemistry was influenced in a complicated fashion by various factors including substituent effects, both steric and electronic, solvents, and the presence of strongly coordinating additives, tetramethylethylenediamine and hexamethylphosphoramide.On the basis of the cyclizable probe experiments, the observed regiochemistry was interpreted as follows. (a) The reaction proceeds by two alternative pathways, a polar one and single electron transfer (SET), the extent of each path being influenced by the variable factors and (b) a polar pathway favors coupling at the phenyl-substituted site (C-1), while in the case of SET the C-C bond formation occurs predominantly at the site far from the phenyl substituent (C-3).
- Tanaka, Jiro,Nojima, Masatomo,Kusabayashi, Shigekazu
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p. 3391 - 3397
(2007/10/02)
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- Reductive Dimerization of Allyl and Benzyl Halides in Pb/n-Bu4NBr-DMF and PbBr2/Al-DMF Systems
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Reductive dimerization of allyl and benzyl halides has been performed by treatment with Pb/n-Bu4NBr and catalytic PbBr2/Al in N,N-dimethylformamide.
- Tanaka, Hideo,Yamashita, Shiro,Toru, Sigeru
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p. 1951 - 1953
(2007/10/02)
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- Hexacarbonylmolybdenum(0)-Catalyzed Reductive Coupling of Allylic Acetates
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The reaction of allylic acetates with zinc in the presence of a catalytic amount of hexacarbonylmolybdenum(0) led to reductive coupling for the formation of a 1,5-diene framework.Reductive coupling of nerolidyl acetate provided squalene and its isomers in high yield.
- Masuyama, Yoshiro,Otake, Kiyotaka,Kurusu, Yasuhiko
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p. 1527 - 1528
(2007/10/02)
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- Reaction of 1-Aryl-3-chloropropenes with Grignard Reagents. Nucleophilic Substitution versus Single-electron Transfer
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The reactions of ambident 1-aryl-3-chloropropenes (1a-e) with a series of Grignard reagents, R'MgY (R' = Me, Pr, Ph, Pri, But; Y = Br, I), were carried out in diethyl ether (EE) and tetrahydrofuran (THF).The products were a mixture of two alkylation products (2) and (3), and three dimerization products (4)-(6).The alkylation:dimerization ratio and the composition of the two alkylation products were a marked function of substituent electronic effects in the chlorides (1a-e), R' or Y of R'MgY, and solvent.On the basis of the stereochemistry of alkylation, cyclizable probe experiments, and the effect of the addition of FeCl3 on product composition, the following conclusions were obtained.First, dimers (4)-(6) are most likely to be produced by a mechanism involving single-electron transfer (SET).Second, for the formation of alkylation products (2) and (3), three alternative pathways contribute depending on the nature of R'MgY and solvent, (a) competitive SN2-SN2' pathways in the reaction of R'MgBr in EE, (b) a process involving SET in the reaction with R'MgI in EE, and (c) SN2 pathways in the reaction of R'MgBr in THF.
- Muraoka, Kiyoshige,Nojima, Masatomo,Kusabayashi, Shigekazu,Nagase, Shigeru
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p. 761 - 768
(2007/10/02)
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- Reaction of 1-Arylpropenyl-lithium with t-Alkyl Bromides. The Influence of Substituent Electronic Effects and Additives on the Course of the Reaction
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The reaction of 1-arylpropenyl-lithium (1a-c) with t-alkyl bromides proceeds by either a nucleophilic substitution or single electron transfer mechanism, the preferred pathway being a function of electronic substituent effects and the absence or presence of tetramethylethylenediamine or hexamethylphosphoramide.
- Tanaka, Jiro,Nojima, Masatomo,Kusabayashi, Shigekazu
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p. 242 - 244
(2007/10/02)
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- PALLADIUM-CATALYZED COUPLING OF ALLYLIC ACETATES WITH ZINC
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Allylic acetates were coupled with zinc dust in the presence of a catalytic amount of to give the corresponding 1,5-dienes under mild conditions in high yields.Significant cosolvent effects were found with methanol or 1,2-ethanediol in tetrahydrofuran.
- Sasaoka, Shin-ichi,Yamamoto, Taku,Kinoshita, Hideki,Inomata, Katsuhiko,Kotake, Hiroshi
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p. 315 - 318
(2007/10/02)
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- New Method for Coupling Allylic Halides: Use of Te2- Species
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A variety of allylic halides were treated with Te2- (generated in situ) to afford coupled 1,5-dienes (average yield 78percent for 11 examples).Mechanistic studies establish that bisallylic tellurides are produced, and these decompose into allylic radicals which then dimerize.
- Clive, Derrick L.J.,Anderson, Paul C.,Moss, Neil,Singh, Alok
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p. 1641 - 1647
(2007/10/02)
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- Electro-organic Reactions. Part 16. The Preparative-scale Cathodic Hydrogenolysis and Coupling of Benzyl-, Allyl-, Cinnamyl-, and Polyenylphosphonium salts
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An investigation of the cathodic reduction of benzyltriphenylphosphonium nitrate confirms that optimum yields of the product of coupling (bibenzyl) are formed at an aluminium cathode using high current densities and in dimethylformamide or hexamethylphosphoramide solution.The cathodic reduction of allylphosphonium salts gives mainly cleavage; e.g. α-farnesene (5) is obtained in 32percent yield from the corresponding farnesylphosphonium salt.Moderately efficient coupling (ca. 30percent) is observed for the electro-reduction of trans-cinnamyltriphenylphosphonium nitrate (6) and a C15 polyenylphosphonium salt (7).The products of coupling have been fully characterised; the relative proportions of positional isomers are apparently dictated by steric factors.
- Utley, James H. P.,Webber, Andrew
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p. 1154 - 1160
(2007/10/02)
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