- Catalytic Chemoselective and Stereoselective Semihydrogenation of Alkynes to E-Alkenes Using the Combination of Pd Catalyst and ZnI2
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An efficient E-selective semihydrogenation of internal alkynes was developed under low dihydrogen pressure and low reaction temperature from commercially available reagents: Cl2Pd(PPh3)2, Zn0, and ZnI2. Kinetic studies and control experiments underline the significant role of ZnI2 in this process under H2 atmosphere, establishing that the transformation involves syn-hydrogenation followed by isomerization. This simple and easy-to-handle system provides a route to E-alkenes under mild conditions.
- Maazaoui, Radhouan,Abderrahim, Raoudha,Chemla, Fabrice,Ferreira, Franck,Perez-Luna, Alejandro,Jackowski, Olivier
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supporting information
p. 7544 - 7549
(2019/01/03)
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- Enabling the Rearrangement of Unactivated Allenes to 1,3-Dienes by Use of a Palladium (0)/Boric Acid System
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A redox neutral rearrangement of an allene to a 1,3-diene by means of a unique palladium hydride complex is reported. The palladium hydride complex is generated from a simple Pd 0 source and boric acid [B(OH) 3 ], which is typically identified as a waste by-product of the Suzuki-Miyaura reaction. A mechanism for this transformation using this novel palladium hydride complex is presented; using a direct sample loop and flow injection ESI-HRMS analysis we have detected and identified key π-allylpalladium complexes that support the addition of the palladium hydride complex to the allene.
- Al-Jawaheri, Yassir,Turner, Matthew,Kimber, Marc C.
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p. 2329 - 2336
(2018/06/15)
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- Synthesis of 1,3-Dienes via a Sequential Suzuki-Miyaura Coupling/Palladium-Mediated Allene Isomerization Sequence
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We report a facile method for the synthesis of 1,3-dienes by a sequential process consisting of a palladium-catalyzed, base-free, Suzuki-Miyaura coupling/isomerization sequence. This sequence couples boronic acids with propargyl alcohols, generating the requisite allene in situ, followed by conversion of the unactivated allene to its 1,3-diene via a hydro-palladation/dehydro-palladation process. This process is general for a range of boronic acids, including boronic acids with electron-donating and -withdrawing groups, as well as heteroarylboronic acids. Key to this process is the boric acid byproduct of the base-free Suzuki-Miyauru coupling, which generates the required palladium-hydrido complex [H-PdII-OB(OH)2] required for the isomerization.
- Al-Jawaheri, Yassir,Kimber, Marc C.
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supporting information
p. 3502 - 3505
(2016/07/23)
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- Stereoselective synthesis of 1,3-dienes from propargylic alcohols by LiAlH4/AlCl3
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Herein we report that LiAlH4/AlCl3 is a very efficient reagent for the reductive dehydration of aryl propargylic alcohols in tetrahydrofuran solvent at reflux to give 1,3-dienes with good yields and high E selection. The reaction con
- Cui, Dong-Mei,Zhu, Kai,Chen, Li,Qi, Lang-Jun,Zhang, Cheng-Zhu,Zheng, Chen
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supporting information
p. 2380 - 2384
(2013/07/26)
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- Gold-catalyzed isomerization of unactivated allenes into 1,3-dienes under ambient conditions
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We have developed a gold-catalyzed isomerization of unactivated allenes into 1,3-dienes with nitrosobenzene as an additive. This reaction proceeded almost exclusively at room temperature for highly substituted allenes. The utility of this reaction is manifested by the development of one-pot [4+2]-cycloaddition of allenes and reactive alkenes.
- Ting, Chun-Ming,Hsu, Yi-Ling,Liu, Rai-Shung
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supporting information; experimental part
p. 6577 - 6579
(2012/07/31)
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- Ligand effects on the stereochemical outcome of suzuki-miyaura couplings
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The ligands associated with various Pd catalysts play a crucial role in determining the stereochemistry of cross-couplings between boronic acids and Z-alkenyl halides. A ligand on palladium has been found that leads to the desired products under mild conditions and in high yields that, in most cases, retain their Z-olefin geometry.
- Lu, Guo-Ping,Voigtritter, Karl R.,Cai, Chun,Lipshutz, Bruce H.
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experimental part
p. 3700 - 3703
(2012/06/15)
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- Arylation and vinylation of alkenes based on unusual sequential semipinacol rearrangement/Grob fragmentation of allylic alcohols
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(Chemical Equation Presented) Alkenes can be stereoselectively arylated and vinylated without transition-metal catalyst under mild conditions through an interesting NBS-promoted semipinacol rearrangement and a subsequent unusual NaOH-mediated Grob fragmentation.
- Yuan, Dao-Yi,Tu, Yong-Qiang,Fan, Chun-An
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p. 7797 - 7799
(2008/12/22)
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- Synthesis of (E)-alkenes via hydroindation of C{triple bond, long}C in InCl3-NaBH4 system
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In InCl3-NaBH4-MeCN system, terminal aryl alkynes could couple with aryl iodides and bromides to give disubstituted alkenes via hydroindation of C{triple bond, long}C. In the similar way, (E)-alkenylsilanes were synthesized via reduction of alkynylsilanes in tetrahydrofuran (THF) in high yields. The processes showed high regio- and stereoselectivity.
- Wang, Chunyan,Yan, Lei,Zheng, Zhiguo,Yang, Deyu,Pan, Yuanjiang
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p. 7712 - 7717
(2007/10/03)
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- The cross-coupling reaction of vinylindiums generated via hydroindation of terminal alkynes with diaryliodoniums salts
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In InCl3-NaBH4-MeCN system, vinylindiums generated by hydroindation of aryl terminal alkynes can undergo cross-coupling reaction with diaryliodonium salts high regio- and stereoselectively. But under the same conditions, the aliphatic terminal alkynes do not react very well.
- Xue, Zhao,Yang, Deyu,Wang, Chunyan
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p. 247 - 250
(2007/10/03)
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- Heck reaction of vinyl bromides with alkenes in the presence of a tetraphosphine/palladium catalyst
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Through the use of [PdCl(C3H5)]2- cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as a catalyst, a range of vinyl bromides undergo Heck reaction with a wide variety of alkenes leading selectively to the corresponding 1,3-dienes in good yields. Furthermore, it can be used at low loading even for reactions of sterically hindered vinyl bromides.
- Berthiol, Florian,Doucet, Henri,Santelli, Maurice
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p. 841 - 844
(2007/10/03)
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- One-pot transformation of silyl enol ethers into 1,3-dienes: In situ generation of alkenyl nonaflates and subsequent Heck reactions - Scope and limitations
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Palladium-catalysed reactions between methyl acrylate and the isolated alkenyl nonaflates 2a, 2d and 2e proceed without difficulties, furnishing the desired 1,3-dienes 3, 14 and 15 in good yields. The use of other alkenyl nonaflates and olefins in this Heck reaction was also examined. The main purpose of this study was the development of an in situ generation of the required alkenyl nonaflates 2 from the corresponding silyl enol ethers 1 and their one-pot transformation into 1,3-dienes. Thus, the previously described fluoride-promoted exchange of the trimethylsilyl substituent of typical enol ethers 1 for a nonafluorobutylsulfonyl group was directly combined with the palladium-catalysed coupling step. This sequence allowed the efficient transformation of a variety of silyl enol ethers 1 into highly substituted 1,3-dienes in a practical one-pot procedure. The scope and limitations, together with the chemo- and stereoselectivity, of this process are discussed. A particular intriguing example involves a one-pot synthesis of silyl enol ether 1j by means of a Diels-Alder reaction, subsequent nonaflation and a Heck reaction with tert-butyl acrylate, furnishing the highly functionalised 1,3-diene 30 in good overall yield. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
- Lyapkalo, Ilya M.,Webel, Matthias,Reissig, Hans-Ulrich
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p. 3646 - 3658
(2007/10/03)
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- Polylithiation of thioethers: A versatile route for polyanionic synthons
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The successive reaction of phenyl vinyl thioether (1) with n-butyllithium and an electophile [E1=PhCHO, (CH2)4CO, (CH2)5CO] in THF at - 78°C gives, after hydrolysis, the expected methylenic hydroxy thioethers (2). Deprotonation of 2 with n-butyllithium followed by a DTBB-catalysed lithiation and reaction with a second electrophile [E2=tBuCHO, PhCHO, Me2CO, (CH2)5CO], at - 78°C, gives after hydrolysis the corresponding methylenic diols 3. The same diols can be prepared starting from 1 in a one-pot process without isolation of the hydroxy thioether 2. The same methodology was applied to the cyclopropyl phenyl thioether (4), cyclopropyl 1,3-diols 5 {E1=tBuCHO, PhCHO, [Me(CH2)4]2CO, (CH2)5CO, (CH2)7CO; E2=tBuCHO, Me2CO, (CH2)5CO} being isolated in moderate yields. The successive treatment of bis(phenylthio)methane (7) with: (a) n-butyllithium at 0°C, (b) a carbonyl compound [E1=tBuCHO, Me2CO, Et2CO, (CH2)5CO] at - 40°C, (c) lithium and catalytic amount of DTBB (5%) and (d) a second carbonyl compound [E2=iPrCHO, tBuCHO, Me2CO, Et2CO, (CH2)5CO] both at - 78°C leads, after hydrolysis, to the expected dihydroxy thioethers 8. When after step (d), a second DTBB-catalysed lithiation is performed at temperatures ranging between - 78 and 20°C, the corresponding allylic alcohols 9 were isolated. Finally, treatment of alcohols 9 with a few drops of 6 M hydrochloric acid gives dienes 10 in almost quantitative yields.
- Yus, Miguel,Gutiérrez, Ana,Foubelo, Francisco
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p. 4411 - 4422
(2007/10/03)
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- Methane-derived polyanionic synthons from bis(phenylthio)methane
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Successive treatment of bis(phenylthio)methane (1) with (a) n-butyllithium at 0°C, (b) a carbonyl compound [(t)BuCHO, Me2CO, Et2CO, (CH2)5CO] at -40°C, (c) lithium and a catalytic amount of DTBB (5%) and (d) a s
- Foubelo, Francisco,Gutierrez, Ana,Yus, Miguel
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p. 8177 - 8180
(2007/10/03)
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- Heck Reactions Starting from Silyl Enol Ethers - A Simple One-Pot Nonaflation-Coupling Procedure for the Synthesis of 1,3-Dienes
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Starting from silyl enol ether 4 the corresponding alkenylnonaflate 5 was generated by treatment with nonafluorobutanesulfonyl fluoride (NfF) and a catalytic amount of tetra-n-butylammonium fluoride (TBAF). By Pd-catalysis 5 was directly Heck-coupled with
- Webel, Matthias,Reissig, Hans-Ulrich
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p. 1141 - 1142
(2007/10/03)
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- A Conformational Study of Two Jet-Cooled Conjugated Styryl Cyclohexenes
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The S1 0 resonance-enhanced ionization spectra are presented for two jet-cooled cyclohexene compounds, 2-(trans-β-styryl)-1,3,3-trimethylcyclohexene and 1-(trans-β-styryl)-cyclohexene, in which the cyclohexene ring is formally conjugated to a styryl group.In the trimethyl-substituted derivative, strong steric interactions between the cyclohexene ring and styryl group are present, similar to those found in the retinal system, which significantly influence the ground-state molecular conformation.Both of these styryl cyclohexenes exhibit spectra that are dominated by an intense origin transition, indicating little change in molecular geometry between the two electronic states.In 2-(trans-β-styryl)-1,3,3-trimethylcyclohexene, two peaks at 34 441 and 34 452 cm-1 are assigned origin transitions of different molecular conformations on the basis of power saturation experiments.A relationship between the origin transition energy and the torsional angle of the cyclohexene ring is derived and then used to determine the ground-state equilibrium torsional geometry for both compounds.The two conformations of 2-(trans-β-styryl)-1,3,3-trimethylcyclohexene are determined to have the cyclohexene ring tilted +/- 73 deg C out of the plane of the conjugated styryl system while in 1-(trans-β-styryl)-cyclohexene the cyclohexene double bond is found to be 14-21 deg from a planar, fully conjugated conformation.
- Finley, J. P.,Cable, J. R.
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p. 3950 - 3956
(2007/10/02)
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- Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
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The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
- Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
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p. 856 - 878
(2007/10/02)
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- A HIGHLY STEREOSELECTIVE SYNTHESIS OF SUBSTITUTED BUTADIENES AND CONJUGATED POLYENES
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A highly stereoselective synthesis of 1,3-butadienes and its higher enyl analogs has been developed through thermal dehydrative ring opening of cyclopropyl carbinols in dimethylsulphoxide.
- Patro, Balaram,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
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p. 809 - 812
(2007/10/02)
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- PALLADIUM CATALYZED CROSS-COUPLING REACTIONS OF ALKENYL (PHENYL) IODONIUM SALTS WITH ORGANOTIN COMPOUNDS
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Alkenyl (phenyl) iodonium salts undergo cross-coupling with both vinyl and allyl trialkyltin compounds stereoselectively and at room temperature.Mild conditions are attributed to the high reactivity of Pd(0) toward the electrophilic hypervalent iodine molecule.
- Moriarty, Robert M.,Epa, W. Ruwan
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p. 4095 - 4098
(2007/10/02)
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- THE CONDENSATION OF ORGANIC CHLORIDES WITH STYRENE CATALYZED BY A NICKEL COMPLEX IN THE PRESENCE OF ZINC
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Aryl chlorides and cyclohexenyl chloride react with styrene in acetonitrile at 65 deg C in the presence of a nickel complex and zinc to give stilbenes and β-substituted styrenes.This reaction is accompanied by the simultaneous oligomerization of the styre
- Lebedev, S. A.,Pedchenko, V. V.,Lopatina, V. S.,Berestova, S. S.,Petrov, E. S.
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p. 1312 - 1314
(2007/10/02)
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- Palladium-catalyzed cross-coupling reaction of alkenylalkoxysilanes with aryl and alkenyl halides in the presence of a fluoride ion
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Alkenyl-monoalkoxydimethylsilanes, dialkoxymethylsilanes, and trialkoxysilanes undergo palladium catalyzed cross-coupling reaction with alkenyl and aryl halides in the presence of tetra-n-butylammonium fluoride. A one-pot transformation of a homopropargyl
- Tamao,Kobayashi,Ito
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p. 6051 - 6054
(2007/10/02)
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- (Cycloalkylidenemethyl)triphenylphosphonium Salts as Versatile Intermediate Reagents
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The (cycloalkylidenemethyl)triphenylphosphonium salts 2b-d were synthesized in high yields by phenylselenylation of (cycloalkylmethylene)triphenylphosphoranes with benzeneselenenyl bromide to the triphenylphosphonium salts 1b-d and subsequent oxidative elimination of the phenylseleno moiety, while the synthesis of the (cyclopropylidenemethyl)triphenylphosphonium salt 2a was unsuccessful.Hydrolysis of 2b-d in aqueous THF and methanol containing sodium hydroxide was studied.The reactions of the (cyclohexylidenemethyl)phosphonium salt 2d and 1.1 equiv of butyllithium with aldehydes 9 gave alkenylcyclohexenes 10d-f in 56-81percent yields, whereas similar reactions using 1.5 equiv and 2 equiv of butyllithium produced allenes 11d-f as major products together with small amounts of 10d,e.Similar reactions of the (cyclopentylidenemethyl)phosphonium salt 2c and butyllithium with 9 gave alkenylcyclopentenes 10a-c in 56-80percent yields, regardless of the amount of butyllithium used.The formation mechanism of 10 and 11 was discussed.
- Minami, Toru,Shikita, Shoji,So, Shuichiro,Nakayama, Minoru,Yamamoto, Izumi
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p. 2937 - 2942
(2007/10/02)
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