- Copper(0) nanoparticle catalyzed Z-Selective Transfer Semihydrogenation of Internal Alkynes
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The use of copper(0) nanoparticles in the transfer semihydrogenation of alkynes has been investigated as a lead-free alternative to Lindlar catalysts. A stereo-selective methodology for the hydrogenation of internal alkynes to the corresponding (Z)-alkenes in high isolated yields (86% average) has been developed. This green and sustainable transfer hydrogenation protocol relies on non-noble copper nanoparticles for reduction of both electron-rich and electron-deficient, aliphatic-substituted and aromatic- substituted internal alkynes. Polyols, such as ethylene glycol and glycerol, have been proven to act as hydrogen sources, and excellent stereo- and chemoselectivity have been observed. Enabling technologies, such as microwave and ultrasound irradiation are shown to enhance heat and mass transfer, whether used alone or in combination, resulting in a decrease in reaction time from hours to minutes. (Figure presented.).
- Moran, Maria Jesus,Martina, Katia,Bieliunas, Vidmantas,Baricco, Francesca,Tagliapietra, Silvia,Berlier, Gloria,De Borggraeve, Wim M.,Cravotto, Giancarlo
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p. 2850 - 2860
(2021/05/06)
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- Methanol as the Hydrogen Source in the Selective Transfer Hydrogenation of Alkynes Enabled by a Manganese Pincer Complex
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The first base metal-catalyzed transfer hydrogenation of alkynes with methanol is described. An air and moisture stable manganese pincer complex catalyzes the reduction of a variety of different alkynes to the corresponding (Z)-olefins in high yields. The
- Sklyaruk, Jan,Zubar, Viktoriia,Borghs, Jannik C.,Rueping, Magnus
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supporting information
p. 6067 - 6071
(2020/08/28)
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- Mizoroki-Heck Cross-Coupling of Bromobenzenes with Styrenes: Another Example of Pd-Catalyzed Cross-Coupling with Potential Safety Hazards
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The potential safety hazards associated with the Mizoroki-Heck cross-coupling of bromobenzenes with styrenes were evaluated. The heat output from the reaction in various solvents was comparable in a variety of solvents; however, the rate of reaction was significantly faster in the presence of water. Thermal stability evaluation of the postreaction mixtures in DMSO and 3:1 DMSO/water by differential scanning calorimetry indicated that the onset temperatures of thermal decomposition were significantly lower than that of neat DMSO. Evaluation of the substrate scope revealed that the substitution pattern on the bromobenzene did not affect the heat output. The reaction rate of electron-deficient bromobenzenes was slower than that of the electron-rich bromobenzenes. In general, substituted styrenes afforded similar magnitudes of exotherms; however, the reaction rate of bromobenzene with 2-methylstyrene was significantly slower than the other studied styrenes. The predicted heat of reaction using the density functional theory method, B3LYP, was in good agreement with the experimental data. Such excellent agreement suggests that this calculation method can be used as a preliminary tool to predict heat of reaction and avoid exothermic reaction conditions. In many of the studied cases, the maximum temperature of a synthesis reaction was considerably higher than the solvent boiling point and thermal decomposition onset temperatures when the reaction was performed in DMSO or 3:1 DMSO/water. It is crucial to understand the thermal stability of the reaction mixture to design the process accordingly and ensure the reaction temperature is maintained below the onset temperature of decomposition to avoid potential runaway reactions.
- Yang, Qiang,Sane, Neeraj,Klosowski, Daniel,Lee, Melissa,Rosenthal, Tay,Wang, Nick X.,Wiensch, Eric
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p. 2148 - 2156
(2019/11/02)
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- Ligand-controlled iridium-catalyzed semihydrogenation of alkynes with ethanol: highly stereoselective synthesis of E- and Z-alkenes
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A ligand-controlled iridium-catalyzed semihydrogenation of alkynes to E- and Z-alkenes with ethanol was developed. Effective selectivity control was achieved by ligand regulation. The use of 1,2-bis(diphenylphosphino)ethane (DPPE) and 1,5-cyclooctadiene (COD) was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 40 alkenes, with good stereoselectivities. The value of our approach in practical applications was investigated by studying the effects of pinosylvin and 4,4′-dihydroxystilbene (DHS) on zebrafish as a vertebrate model.
- Yang., Jinfei,Wang, Chengniu,Sun, Yufeng,Man, Xuyan,Li, Jinxia,Sun, Fei
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supporting information
p. 1903 - 1906
(2019/05/02)
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- Selective Semihydrogenation of Alkynes with N-Graphitic-Modified Cobalt Nanoparticles Supported on Silica
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For the first time N-graphitic-modified cobalt nanoparticles (Co/phen@SiO2-800) are shown to be active in the semihydrogenation of alkynes to alkenes. Key to success for efficient catalysis is both the modification of the metal nanoparticles by nitrogen-doped graphitic layers and the use of silica as support. Several internal alkynes are converted to the Z isomer in high yields with up to 93% selectivity. In addition, a variety of terminal alkynes, including sensitive functionalized compounds, are readily converted into terminal alkenes. Notably, this non-noble-metal catalyst allows for the purification of alkenes by selective hydrogenation of the corresponding alkyne in the presence of an excess of olefin.
- Chen, Feng,Kreyenschulte, Carsten,Radnik, J?rg,Lund, Henrik,Surkus, Annette-Enrica,Junge, Kathrin,Beller, Matthias
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p. 1526 - 1532
(2017/08/15)
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- Z-Stereoselective Aza-Peterson Olefinations with Bis(trimethylsilane) Reagents and Sulfinyl Imines
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Highly stereoselective aza-Peterson olefinations from bench-stable α,α-bis(trimethylsilyl)toluene reagents and N-substituted imines have been achieved using TMSO-/Bu4N+ as Lewis base activator in THF. Remarkably, and for the first time, N-t-butanesulfinyl imines were utilized for the synthesis of Z-stilbenes with excellent selectivities, while N-aryl imines generated E-stilbenes under identical reaction conditions. The protocol proved general for numerous examples with low molecular weight byproducts formed. The origin of the Z-selectivity is proposed to be a result of diastereoselective addition to N-t-butanesulfinyl imines followed by syn-elimination of an in situ formed hypervalent silicate.
- Das, Manas,OShea, Donal F.
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supporting information
p. 336 - 339
(2016/02/03)
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- Immobilization and continuous recycling of photoredox catalysts in ionic liquids for applications in batch reactions and flow systems: Catalytic alkene isomerization by using visible light
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A catalytic (E)- to (Z)-isomerization of olefins using a photoredox catalyst under mild reaction conditions is presented. A variety of (Z)-alkenes can be prepared in the presence of visible light. A new reaction system allows an easy and efficient scale-up, as well as a continuous flow process in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by simple phase separation. Catalytic (E)- to (Z)-isomerizations of olefins under mild conditions can be achieved by use of a photosensitizer and visible light. A new reaction system such as depicted allows an easy and efficient scale-up, as well as continuous flow processes in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by phase separation.
- Fabry, David C.,Ronge, Meria A.,Rueping, Magnus
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supporting information
p. 5350 - 5354
(2015/03/30)
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- Stereoselective iron-catalyzed alkyne hydrogenation in ionic liquids
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Iron(0) nanoparticles in ionic liquids (ILs) have been shown to catalyse the semi-hydrogenation of alkynes. In the presence of a nitrile-functionalised IL or acetonitrile, stereoselective formation of (Z)-alkenes was observed. The biphasic solvent system allowed facile separation and re-use of the catalyst. The Royal Society of Chemistry 2014.
- Gieshoff, Tim N.,Welther, Alice,Kessler, Michael T.,Prechtl, Martin H.G.,Jacobi Von Wangelin, Axel
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p. 2261 - 2264
(2014/03/21)
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- Unequivocal experimental evidence for a unified lithium salt-free wittig reaction mechanism for all phosphonium ylide types: Reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products
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The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
- Byrne, Peter A.,Gilheany, Declan G.
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p. 9225 - 9239
(2012/07/14)
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- A highly efficient and recyclable fluorous palladium catalyst for Heck reactions in water
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A fluorous nano-palladium catalyst has been synthesized and characterized. The catalyst is highly active for the Heck reaction of aryl halides with substituted styrenes in water under air. The corresponding Heck products were obtained in high yields with good stereoselectivity (E/Z up to 98:2). In addition, the catalyst could be recovered by fluorous liquid-liquid separation and reused four times without significant loss of activity or stereoselectivity. Graphical Abstract: The Heck reaction catalyzed by a new fluorous nano-palladium catalyst in water to afford the products in high yields has been described. The catalyst can be recovered by fluorous liquid-liquid separation and reused for several times without significant loss of activity. [Figure not available: see fulltext.]
- Wan, Li,Cai, Chun
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experimental part
p. 747 - 750
(2012/06/30)
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- A highly tunable stereoselective olefination of semistabilized triphenylphosphonium ylides with N -Sulfonyl imines
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The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.
- Dong, De-Jun,Li, Hai-Hua,Tian, Shi-Kai
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supporting information; experimental part
p. 5018 - 5020
(2010/06/13)
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- Catalytic direct arylation with aryl chlorides, bromides, and iodides: Intramolecular studies leading to new intermolecular reactions
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A catalyst for the intramolecular direct arylation of a broad range of simple and heterocyclic arenes with aryl iodides, bromides, and chlorides has been developed. These reactions occur in excellent yield and are highly selective. Studies with aryl iodides substrates revealed that catalyst poisoning occurs due to the accumulation of iodide in the reaction media. This can be overcome by the addition of silver salts which also permits these reactions to occur at lower temperature. The utility of the methodology is illustrated by a rapid synthesis of a carbazole natural product and by the synthesis of sterically encumbered tetra-ortho-substituted biaryls via ring-opening reactions of the direct arylation products. Mechanistic investigations have provided insight into the catalyst's mode of action and show the presence of a kinetically significant C-H bond cleavage in palladium-catalyzed direct arylation of simple arenes. Knowledge garnered from these studies has led to the development of new intermolecular arylation reactions with previously inaccessible arenes, opening the door for the development of other new direct arylation processes.
- Campeau, Louis-Charles,Parisien, Mathieu,Jean, Annie,Fagnou, Keith
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p. 581 - 590
(2007/10/03)
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- Co-operative ortho-effects on the Wittig reaction. Interpretation of stereoselectivity in the reaction of ortho-halo-substituted benzaldehydes and benzylidenetriphenylphosphoranes
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The E/Z ratios of the stilbenes 1 formed in the Wittig reaction of ortho-halo substituted benzyltriphenylphosphonium salts 2 and benzaldehydes 3 were determined. It was found that there is a co-operative effect of one ortho-halo group on each of the two reacting partners which increases Z-selectivity, but two such groups on the same reactant gives high E-selectivity. The effects are strong enough to be preparatively significant in certain cases and can be interpreted within the modern framework of the Wittig mechanism established by Vedejs and co-workers.
- Dunne, Eoin C,Coyne, éamonn J,Crowley, Peter B,Gilheany, Declan G
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p. 2449 - 2453
(2007/10/03)
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- Benzannulated Isobenzofurans
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A number of arynes, generated by treatment of haloarenes with sodium or potassium amide in tetrahydrofuran, were trapped with furan.The resulting dihydro epoxy arenes were converted into the following annulated isobenzofuran derivatives by using reverse Diels-Alder methodology: naphthofuran, phenanthrofuran, pyrenofuran, pyrenofuran, anthrafuran, phenanthrofuran and phenathrofuran.Bimolecular rate constants for the addition of maleic anhydride to these furans were measured, and were correlated with the Herndon structure count.Addition of arynes to selected members of this furan series yielded adducts which were deoxygenated to afford polycyclic aromatic hydrocarbons.
- Moursounidis, John,Wege, Dieter
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p. 235 - 249
(2007/10/02)
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- OLEFIN SYNTHESIS VIA THE LITHIUM DERIVATIVES OF THE N,N,N',N'-TETRAMETHYLDIAMIDES OF ARYLMETHANEPHOSPHONIC ACIDS. 2. SYNTHESIS OF SOME (Z)-ORTHO AND PARA SUBSTITUTED STILBENES
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The reaction of the lithium derivatives of N,N,N',N'-tetramethyldiamides of arylmethanophosphonic acids (1-Li) with ortho- and para-substituted benzaldehydes 2 is studied.Reaction conditions are found for erythro-stereoselective addition of 1 to 2 with high diastereomeric purity (95-99percent) of the rythro adducts 3, 4 (yields 35-72percent).By thermolysis of the adducts in neutral medium the corresponding (Z)-ortho and para-substituted silbenes 5, 6 are obtained.Some factors causing the predominant formation of the erythro adducts 3, 4, as well as the influence of the ortho-substituents on the equilibrium are discussed.
- Petrova, Jordanka,Momchilova, Snejana,Kirilov, Marko
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p. 243 - 250
(2007/10/02)
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