- Palladium-catalyzed cross-coupling of Cr(CO)3-complex chloroarenes with organofluorosilanes
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The palladium-catalyzed cross-coupling of (η6-chlorobenzene) tricarbonylchromium complexes with organofluorosilanes followed by decomplexation afforded aryl-, alkenyl-, and alkynyl-substituted arenes.
- Kang, Suk-Ku,Kim, Won-Yeob
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- New studies of Rh-catalyzed addition of boronic acids under basic conditions in aqueous medium
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Rh-catalyzed C-C bond formation in neat water under basic conditions has been efficiently performed. The addition of various boronic acids to styrene, 2-vinylpyridine, and cyclic α,β-unsaturated ketones has been realized with high selectivity and yield. We have shown that m-TPPTC (tris(m-carboxyphenyl)phosphane trilithium salt) exhibited a higher reactivity compared to TPPTS. These couplings could also be conducted very efficiently under basic and phosphaneless conditions to give functionalized aryl derivatives. The benefits of the additional anionic ligand m-TPPTC lied in the successful recycling experiments of 1,4-addition of phenylboronic acid to cyclohexenone, with no loss of the water-soluble catalyst.
- Amengual, Rémi,Michelet, Véronique,Genêt, Jean-Pierre
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- Tandem Hydrosilylation/o-C-H Silylation of Arylalkynes Catalyzed by Ruthenium Bis(silyl) Aminophosphine Complexes
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An unprecedented reaction via consecutive trans-selective hydrosilylation and o-C-H silylation of arylalkynes with hydrosilanes was developed by use of ruthenium complex catalysts Ru{?°3(Si,O,Si)-xantsil}(CO)(PR3) (R = NC4H8 (1-Pyrr), NC5H10 (1-Pip); xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)). This reaction proceeded with gentle heating at 40-60 °C and afforded novel 2,α-bis-silylated (Z)-stilbene or (Z)-styrene derivatives 2 together with an equimolar amount of (E)-/(Z)-arylalkenes as byproducts. The selectivity of the formation of 2 reached a maximum by employing catalyst 1-Pyrr ligated by the less bulky triaminophosphine P(NC4H8)3 and hydrosilane HSiMe(OSiMe3)2 having moderately bulky and electron withdrawing substituents.
- Kitano, Takeo,Komuro, Takashi,Ono, Rikima,Tobita, Hiromi
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- Convenient Synthesis of Cyclic Trithiocarbonates from 1,2- or 1,3-Dihaloalkanes and Sodium Trithiocarbonate in the Presence of Phase-Transfer Catalyst
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Cyclic trithiocarbonates, such as 1,3-dithiolane-2-thiones and 1,3-dithiane-2-thiones, were conveniently synthesized by treating 1,2- or 1,3-dihaloalkanes with sodium trithiocarbonate in the presence of a phase-transfer catalyst.
- Sugawara, Akira,Sato, Tsukasa,Sato, Ryu
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- Heck reaction catalyzed by phospha-palladacycles in non-aqueous ionic liquids
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Phospha-palladacycles are among the most powerful palladium catalyst systems for the Heck reaction. We have shown the use of non-aqueous ionic liquids (NAILs) as an alternative to traditional molecular solvents for this reaction, with the phospha-palladacycle catalysts resulting in easy product separation, possible catalyst recycling and further increases in catalyst productivity. Preliminary results obtained with bromo- and chloro arenes are presented.
- Herrmann, Wolfgang A.,Boehm, Volker P.W.
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- Manganese chloride-catalyzed cross-coupling and carbonylative cross- coupling of organostannanes with iodonium salts
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The MnCl2-4H2O-catalyzed cross-coupling and carbonylative cross- coupling of organostannanes with hypervalent iodonium salts afforded biaryls and biaryl ketones, respectively.
- Kang, Suk-Ku,Kim, Won-Yeob,Lee, Yong-Tack,Ahn, Sung-Ki,Kim, Jin-Chul
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- Ring-opening metathesis polymerization based pore-size-selective functionalization of glycidyl methacrylate based monolithic media: Access to size-stable nanoparticles for ligand-free metal catalysis
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Monolithic polymeric supports have been prepared by electron-beam-triggered free-radical polymerization using a mixture of glycidyl methacrylate and trimethylolpropane triacrylate in 2-propanol, 1-dodecanol, and toluene. Under appropriate conditions, phase separation occurred, which resulted in the formation of a porous monolithic matrix that was characterized by large (convective) pores in the 30 μm range as well as pores of 7 nm were hydrolyzed by using poly(styrenesulfonic acid) (Mw = 69400 gmol-1, PDI = 2.4). The remaining epoxy groups inside pores of 2(PCy3) 2-(CHPh)]. These immobilized Ru-alkylidenes were further used for the surface modification of the small pores by a grafting approach. A series of monomers, that is, 7-oxanorborn-5-ene-2,3-dicarboxylic anhydride (3), norborn-5ene-2,3-dicarboxylic anhydride (4), N,N-di-2-pyridyl-7-oxanorborn-5- ene-2-carboxylic amide (5), N,N-di-2-pyridyl-norbom-5-ene-2-carboxamide (6), N[2-(dimethylamino)ethyl]bicyclo-[2.2.1]hept-5-ene-2-carboxamide (7), and dimethyl bicyclo[2.2.1]hept-5-en-2-ylphosphonate (8), were used for this purpose. Finally, monoliths functionalized with poly-5 graft polymers were used to permanently immobilize Pd2+ and Pt4+, respectively, inside the pores. After reduction, metal nanoparticles 2nm in diameter were formed. The palladium-nanoparticle-loaded monoliths were used in both Heck- and Suzuki-type coupling reactions achieving turnover numbers of up to 167000 and 63000, respectively.
- Bandari, Rajendar,H?che, Thomas,Prager, Andrea,Dimberger, Klaus,Buchmeiser, Michael R.
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- Palladium-catalyzed cross-coupling of triarylbismuth(V) derivatives with hypervalent iodonium salts
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The palladium-catalyzed cross-coupling of hypervalent iodonium salts with organobismuth(V) derivatives was accomplished with PdCl2 (5 mol%) in CH3CN at room temperature.
- Kang,Ryu,Kim
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- Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
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The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
- López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
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- Fluoride-promoted cross-coupling of chloro(mono-, di-, or triphenyl)germanes with aryl halides in "moist" toluene. Multiple transfer of the phenyl group from organogermane substrates and comparison of the coupling efficiencies of chloro(phenyl)germanes with their corresponding stannane and silane counterparts
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The trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylgermanes undergo Pd-catalyzed cross-couplings with aryl bromides and iodides in the presence of tetrabutylammonium fluoride in toluene with addition of the measured amount of water. One chloride ligand on the Ge center allows efficient activation by fluoride to promote transfer of one, two, or three phenyl groups from the organogermanes. The corresponding chlorophenylstannanes were found to be more reactive than chlorophenylsilanes, which in turn were more effective than chlorophenylgermanes. One chloride ligand on the Ge or Si center allows efficient activation by fluoride to promote transfer of up to three aryl groups from germane or silicon. However, no haloligand was necessary to be present on the Sn center, since tetraphenyltin efficiently transferred up to four phenyl groups during fluoride-promoted couplings with aryl halides. 19F NMR studies suggested formation of the fluorophenylgermanes and the hypervalent germanate species as possible intermediates.
- Pitteloud, Jean-Philippe,Zhang, Zun-Ting,Liang, Yong,Cabrera, Laura,Wnuk, Stanislaw F.
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- Mild and efficient debromination of vic-dibromides to alkenes with fecl36h2o/indium system
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The FeCl36H2O/indium system efficiently causes debromination of various dibromides to the corresponding alkenes in good to excellent yields under mild conditions.
- Woo Yoo, Byung,Woo Choi, Jin,Hye Yang, Min
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- CARBODETELLURATION OF ARYLTELLURIUM(IV) COMPOUNDS: OLEFIN ARYLATION AND AROMATIC COUPLING
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Aryltellurium(IV) compounds react with olefins to give the corresponding arylated olefins in moderate to quantitative yield in the presence of a palladium(II) salt.The reaction proceeds catalytically with respect to the palladium(II) salt if a suitable oxidant, such as t-butyl hydroperoxide or copper(I) or (II) chloride, is added.In the absence of olefin the corresponding biaryls are formed in moderate yield.Transmetalation of tellurium with palladium is a key step of the reaction.
- Uemura, Sakae,Wakasugi, Mikio,Okano, Masaya
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- Synthesis and characterization of pyrazolyl-functionalized imidazolium-based ionic liquids and hemilabile (Carbene)palladium(II) complex catalyzed heck reaction
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Neat reactions of 1-(pyrazolylmethyl)imidazole with an excess of alkyl or polyfluoroalkyl halides at 100°C followed by subsequent metathetical reactions with LiN(SO2CF3)2 or KPF6 at 25°C gave rise to a series of
- Wang, Ruihu,Zeng, Zhuo,Twamley, Brendan,Piekarski, Melissa M.,Shreeve, Jean'ne M.
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- Efficient synthesis of E-stilbenes
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A convenient, high yield, method for the synthesis of E-stilbenes (2a-f and 3) is described starting from benzyl bromides (1a-f) using LDA.
- Mali,Jagtap
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- Palladium-catalyzed cross-coupling of organoboron compounds with iodonium salts and iodanes
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The palladium-catalyzed cross-coupling reaction of iodinanes (iodonium salts and iodanes) with organoboron compounds to form carbon-carbon bonds was achieved at ambient temperature under aqueous conditions in the absence of base. Coupling of phenylboronic acid with diphenyliodonium tetrafluoroborate in the presence of Pd(PPh3)4 (0.2 mol %) or Pd(OAc)2 (0.2 mol %) under aqueous conditions gave biphenyl in almost quantitative yield. Under the same conditions, substituted boronic acids, boronates, and trialkylboranes were readily coupled with diaryl-, alkenyl-, and alkynyliodonium salts. Finally, the iodanes ArI(OH)OTs underwent cross-coupling with boronic acids, boronates, and trialkylboranes to afford biphenyls and aryl-substituted alkenes.
- Kang, Suk-Ku,Lee, Hong-Woo,Jang, Su-Bum,Ho, Pil-Su
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- A Convenient Reagent for the Intermolecular Coupling of Aldehydes and Ketones to Form Olefins
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When aldehydes or ketones are treated with titanium tetrachloride and amalgamated magnesium turnings in tetrahydrofuran at 0 deg C for 2 h and subsequently under reflux for 24 h, reductive coupling occurs to give olefin in high yield.The optimum ratio of carbonyl substrate to titanium reagent was found to be 1 : 4.Examples of symmetrical and mixed couplings are given.Intramolecular coupling was not successful.
- Carroll, Anthony R.,Taylor, Walter C.
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- Tuning the Selectivity of Palladium Catalysts for Hydroformylation and Semihydrogenation of Alkynes: Experimental and Mechanistic Studies
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Here, we describe a selective palladium catalyst system for chemodivergent functionalization of alkynes with syngas. In the presence of an advanced ligand L2 bearing 2-pyridyl substituent as a built-in base, either hydroformylation or semihydrogenation of diverse alkynes occurs with high chemo- and stereoselectivity under comparable conditions. Mechanistic studies, including density functional theory (DFT) calculations, kinetic analysis, and control experiments, revealed that the strength and concentration of acidic cocatalysts play a decisive role in controlling the chemoselectivity. DFT studies disclosed that ligand L2 not only promotes heterolytic activation of hydrogen similar to frustrated Lewis pair (FLP) systems in the hydrogenolysis step for hydroformylation but also suppresses CO coordination to promote semihydrogenation under strong acid conditions. This switchable selectivity provides a strategy to design new catalysts for desired products.
- Beller, Matthias,Ge, Yao,Jackstell, Ralf,Jiao, Haijun,Liu, Jiawang,Wei, Duo,Wei, Zhihong,Yang, Ji
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- Electron-transfer Reduction of Protons to Hydrogen mediated by a Phenyl-lithium-activated Fe4S4 Cluster
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A synthetic Fe4S4 cluster mediates the transfer of electrons from phenyl-lithium to protons from benzenethiol, in a homogeneous system, resulting in the generation of hydrogen.
- Inoue, Hiroo,Sato, Makoto
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- Design of highly porous single-site catalysts through two-step postsynthetic modification of mixed-linker MIL-53(Al)
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Defined mixed-linker metal-organic frameworks based on MIL-53-NH2(Al) were successfully synthesized under ambient pressure, thus, enabling easy scaling up of the synthesis. The two-step postsynthetic modification reaction of these materials with, first, maleic anhydride and, second, palladium(II) acetate resulted in immobilized palladium(II) complexes at the side chain of the linker molecules. The high porosity of the mixed-linker materials was retained throughout the modification process, which was in contrast to a previous study with pure MIL-53-NH2(Al). The novel palladium-containing materials were applied in Heck-type C-C coupling reactions of bromo- or chlorobenzene with styrene, in which they exhibited high catalytic activity and selectivity.
- Gotthardt, Meike A.,Schoch, Roland,Brunner, Tobias S.,Bauer, Matthias,Kleist, Wolfgang
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- Isomerization Behavior of Halostilbene Radical Cations in the Excited States. Two-Color Photochemistry of Stilbene Derivatives
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Two-color laser excitation of (Z)-4,4'-dichlorostilbene and (Z)-4,4'-difluorostilbene with 425- and 500-nm laser pulses in acetonitrile containing 9,10-dicyanoanthracene and biphenyl exhibited a spectral change indicating a rapid conversion of the Z-radic
- Kuriyama, Yasunao,Hashimoto, Fumiko,Tsuchiya, Masahiro,Sakuragi, Hirochika,Tokumaru, Katsumi
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- Photodynamics of the Paterno-Buechi cycloaddition of stilbene to quinone. Unusual modulation of electron-transfer kinetics by solvent and added salt
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Oxetanes are produced in the Paterno-Buechi cycloaddition of stilbene (S) to quinone (Q) via an efficient photoinduced electron transfer. Kinetics analysis of the time-resolved absorption spectra over three distinctive (ps, ns, μs) timescales establishes the coupling (kC) of the initially formed ion-radical pair 3[S+?, Q-?] to the 1,4-biradical ?SQ? as the critical step toward oxetane formation. The (rather slow) rate constant of kC ≤ 107 s-1 in acetonitrile must compete with other faster decay pathways of the ion pair involving ionic separation, ion exchange (with added salt) and back electron transfer. As such, solvent polarity and donicity as well as added salts play an unusually prominent role in modulating the ion-pair microdynamics. Donor-acceptor complexation of the photoexcited quinone with the solvent and cis→trans isomerization of (Z)-stilbene must also be considered in the overall photodynamics of electron transfer.
- Hubig, Stephan M.,Sun, Duoli,Kochi, Jay K.
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- A First Palladium-Catalyzed Aryldegermylation of Styryltrimethylgermanes
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Both β-(E)- and β-(Z)-styryltrimethylgermanes easily reacted with arenediazonium tetrafluoroborates under palladium catalysis to give aryldegermylated products, (E)-PhCH=CHAr and Ph(Ar)C=CH2.On the other hand, the aryldegermylation of α-styrylgermane gave (E)-stilbene derivates with high stereo- and regioselectivities.
- Ikenaga, Kazutoshi,Matsumoto, Satoshi,Kikukawa, Kiyoshi,Matsuda, Tsutomu
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- Kinetics and Pressure Effect in the Thermolysis of Liquid Bibenzyl
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The rate of thermolysis of liquid bibenzyl to toluene and stilbene has been measured as a function of temperature and pressure with upper limits of 400 deg C and 1000 atm (101 MPa).The activation parameters are Eact = 63 kcal, Sact = +9 eu, and Vact = +31 mL.They are consistent with a rate-controlling step involving formation of a widely separated pair of benzyl radicals.The Vact is interpreted in the light of cage effects, and the conventional treatment of diffusive separation and recombination of radical pairs as activated process is called into question.
- Brower, K.R.
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- Cobalt-catalyzed alkenylation of organomagnesium reagents
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Alkenyl iodides, bromides and chlorides react with organomagnesium reagents in THF, in the presence of Co(acac)2 and NMP (9 to 4 equiv.), to give the cross-coupling products in good yields. The reaction is chemoselective (aryl or alkyl bromides, esters and ketones) and stereoselective (≤ 99.5%).
- Cahiez, Gerard,Avedissian, Hovsep
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- Selective Isomerization of cis-Stilbene by Non-Resonant Two-Photon Excitation
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Non-Resonant two-photon excitation induced dramatical cange in the photoreaction pathways of stilbenes.Typically, irradiation of cis-stilbene with 532 nm laser pulses caused only isomerization to trans-stilbene in hexane at room temperature; the cyclization to dihydrophenanthrene was completely suppressed.
- Miyazawa, Takashi,Koshihara, Shin-ya,Segawa, Yusaburo,Kira, Mitsuo
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- THE PALLADIUM-CATALYZED "HEAD-TO-TAIL" CROSS-COUPLING REACTION OF 1-ALKENYLBORANES WITH PHENYL OR 1-ALKENYL IODIDES. A NOVEL SYNTHESIS OF 2-PHENYL-1-ALKENES OR 2-ALKYL-1,3-ALKADIENES VIA ORGANOBORANES
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The reaction of phenyl or 1-alkenyl iodides with 1-alkenyl-1,3,2-benzodioxaboroles readily obtainable via the hydroboration of 1-alkynes, gives the corresponding "head-to-tail" cross-coupling products, 2-phenyl-1-alkenes or 2-alkyl-1,3-alkadienes, in good yields.The reaction is effectively catalyzed by catalytic amounts of palladium compounds in the presence of triethylamine.
- Miyaura, Norio,Suzuki, Akira
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- Molybdenum-Catalyzed Stereospecific Deoxygenation of Epoxides to Alkenes
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Mild and simple catalytic systems consisting of molybdenum(VI) dichloride dioxide [MoO2Cl2] as a catalyst and a phosphine as reductant have been developed for the stereospecific deoxygenation of epoxides to alkenes. The reactions using 1,2-bis(diphenylphosphino)ethane (dppe) and triphenylphosphine (PPh3) proceed with retention and inversion of stereochemistry, respectively. The mild reaction tolerates the presence of various functional groups and affords stereodefined substituted olefins in good yields. (Figure presented.).
- Asako, Sobi,Sakae, Takahisa,Murai, Masahito,Takai, Kazuhiko
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- Heterotriangulene as an electron-transfer mediator in reduction of vic-dibromide compounds
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A novel heterotriangulene derivative and its nonfused analogue were successfully prepared, and their electrochemical and optical properties were studied by cyclic voltammetry measurements and UVvis and photoluminescence analyses. The mediatory use of the heterotriangulene derivative for the electrocatalytic reduction of dibromo compounds was also investigated.
- Inagi, Shinsuke,Kaihatsu, Noriyuki,Kuribayashi, Shunsuke,Fuchigami, Toshio
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- N-Phenylurea as an inexpensive and efficient ligand for Pd-catalyzed Heck and room-temperature Suzuki reactions
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N-Phenylurea was found to constitute a highly efficient, yet low-priced, phosphine-free ligand for the Pd-catalyzed Heck and room-temperature Suzuki reactions of aryl bromides and iodides with very high turnover numbers (ca. 103-104).
- Cui, Xin,Zhou, Yuan,Wang, Na,Liu, Lei,Guo, Qing-Xiang
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- Synthesis of xylylene-bridged dipalladium complexes with imidazole and triazole-based di-N-heterocyclic carbene (NHC) ligands
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The di-N-heterocyclic carbene (NHC) dipalladium complexes, [(PdPyBr2)2(di-NHCimi)] and [(PdPyBr2)2(di-NHCtri)], di-NHCimi and di-NHCtri represent an imidazolylidene and a triazolylidene, respectively, featuring a 1,4-xylylene spacer between the carbene units, have been prepared. The influences of the imidazolylidene and triazolidene backbone and different substituents on the catalytic activity have been investigated in the Mizoroki-Heck reaction of styrene with bromobenzene.
- Du, Yufeng,Tang, Huiling,Ding, Hong,Shi, Yanhui,Cao, Changsheng,Pang, Guangsheng
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- Base-Controlled Heck, Suzuki, and Sonogashira Reactions Catalyzed by Ligand-Free Platinum or Palladium Single Atom and Sub-Nanometer Clusters
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The assumption that oxidative addition is the key step during the cross-coupling reaction of aryl halides has led to the development of a plethora of increasingly complex metal catalysts, thereby obviating in many cases the exact influence of the base, which is a simple, inexpensive, and necessary reagent for this paramount transformation. Here, a combined experimental and computational study shows that the oxidative addition is not the single kinetically relevant step in different cross-coupling reactions catalyzed by sub-nanometer Pt or Pd species, since the reactivity control is shifted toward subtle changes in the base. The exposed metal atoms in the cluster cooperate to enable an extremely easy oxidative addition of the aryl halide, even chlorides, and allow the base to bifurcate the coupling. With sub-nanometer Pd species, amines drive to the Heck reaction, carbonate drives to the Sonogahira reaction, and phosphate drives to the Suzuki reaction, while for Pt clusters and single atoms, good conversion is only achieved using acetate as a base. This base-controlled orthogonal reactivity with ligand-free catalysts opens new avenues in the design of cross-coupling reactions in organic synthesis.
- Fernández, Estefanía,Rivero-Crespo, Miguel A.,Domínguez, Irene,Rubio-Marqués, Paula,Oliver-Meseguer, Judit,Liu, Lichen,Cabrero-Antonino, María,Gavara, Rafael,Hernández-Garrido, Juan C.,Boronat, Mercedes,Leyva-Pérez, Antonio,Corma, Avelino
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- Palladium on calcium carbonate combined to 2-hydroxypropyl-α/β- cyclodextrins: A selective catalytic system for aqueous heck coupling and hydroarylation
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An efficient, selective and recoverable catalytic system for ligand-free aqueous Heck reactions using hydroxypropylated cyclodextrins (HPCDs) and palladium on calcium carbonate (Pd/CaCO3) is highlighted. Remarkably, stereo- and chemoselectivities could be tuned by the cavity size of cyclodextrins, exploiting the relevance of host-guest interactions. UVVis experiments have led to strong evidence concerning an interplay between Pd(II) and α-HPCD, possibly ascribed to a reduction/stabilization effect of CDs. Unexpectedly, hydroarylation was the favored pathway with acrylonitrile which provided access to 3-phenylpropionitrile derivatives without usual hydride donors. Finally, determination of soluble Pd(0/II) via AAS enabled the definition of a predominant homogeneous mechanism in which TONs over 5000 were observed.
- Senra, Jaqueline D.,Malta, Luiz Fernando B.,Souza, Andrea Luzia F.,Aguiar, Lucia C. S.,Antunesa
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- 3,5-Bis(trifluoromethyl)phenyl sulfones in the modified Julia olefination: Application to the synthesis of resveratrol
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The reaction between carbanions derived from alkyl 3,5-bis(trifluoromethyl) phenyl sulfones and aldehydes, affords with good yields and stereoselectivities the corresponding 1,2-disubstituted alkenes through the Julia-Kocienski olefination reaction. This one-pot protocol can be performed using KOH at room temperature or the phosphazene base P4-t-Bu at -78°C, and has been successfully used in a high yielding and stereoselective synthesis of various stilbenes such as resveratrol.
- Alonso, Diego A.,Nájera, Carmen,Varea, Montserrat
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- A Novel and Efficient Route to (E)-Alk-1-enyl Boronic Acid Derivatives from (E)-1-(Trimethylsilyl)alk-1-enes and a Formal Suzuki-Miyaura Cross-coupling Reaction starting with Vinylsilanes
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A novel and highly efficient conversion of vinylsilanes into vinyl boronates is described together with their Suzuki-Miyaura cross-coupling reaction, performed without isolating the intermediate resulting from borodesilylation.
- Farinola, Gianluca M.,Fiandanese, Vito,Mazzone, Luigia,Naso, Francesco
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- Femtosecond Laser Study of the Alignment of Reactant and Products in the Photoisomerization Reactions of cis-Stilbene
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Polarized femtosecond laser studies of the products of the photoisomerization of cis-stilbene demonstrate an unexpectedly high degree of alignment between the cis reactant and trans product transition dipoles and an unexpectedly low degree of alignment between the cis reactant and dihydrophenanthrene (DHP) product transition dipoles.These results are consistent with the reaction toward both trans and DHP involving a significant angular displacement of the ethylene bond.Some possible reasons for this displacement are dicussed.
- Sension, Roseanne J.,Repinec, Stephen T.,Hochstrasser, Robin M.
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- Efficient PEPPSI-themed palladium N-heterocyclic carbene precatalysts for the mizoroki-heck reaction
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Two sets of six PEPPSI (pyridine enhanced precatalyst preparation, stabilization, and initiation) themed palladium complexes of amide-functionalized N-heterocyclic carbenes [PdBr2(NHC)(Py)], where NHC = 1-acetamido-3-R-imidazolin-2-ylidene, 1-acetamido-3-R-benzimidazolin-2- ylidene and Py = pyridine, were prepared. Solid-state structures of all these complexes were determined by single-crystal X-ray diffraction methods. All complexes under scrutiny were found to adopt a trans arrangement with square-planar geometry. These complexes showed excellent catalytic activity toward the Mizoroki-Heck cross-coupling reaction of aryl chlorides and styrene. Benzimidazole-derived complexes exhibited better catalytic activity than imidazole-based complexes. Formation of palladium nanoparticles in the reaction mixture was evidenced by dynamic light scattering and transmission electron microscopy studies and a mercury poisoning experiment, suggesting the possible involvement of palladium nanoparticles in the catalytic reactions.
- Lin, Yong-Chieh,Hsueh, Hsin-Hsueh,Kanne, Shanker,Chang, Li-Kuang,Liu, Fu-Chen,Lin, Ivan J. B.,Lee, Gene-Hsiang,Peng, Shie-Ming
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- Reactions of polyfluorinated cyclohexadienones with diazoalkanes. Part 1. Formation of cyclopropanes from polyfluorinated cyclohexa-2,4-dienones with diazomethane and phenyldiazomethane
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The reaction of 6-chloro-2,3,4,5,6-pentafluorocyclohexa-2,4-dienone (1) with diazomethane gives a mixture of two diastereoisomers of 6-chloro-3a,4,5,6,7a-pentafluoro-3,3a,6,7a-tetrahydrospiro[indazole-7,2′-o xirane] 2a and 2b. In contrast phenyldiazomethane reacts with polyfluorinated cyclohexa-2,4-dienones 1, 9, and 10 in acetonitrile to form the fluorinated 7-phenylbicyclo[4.1.0]hept-4-en-2-ones 4a,b, 11a,b, and 12a,b as the main products. This reaction shows a remarkable dependence on the polarity of the solvent. While a complex mixture of products was formed in pentane, the reaction in acetonitrile proceeds with high stereoselectivity giving only the two endo-isomers.
- Kovtonyuk, Vladimir N.,Kobrina, Ljubov S.,Gatilov, Yurij V.,Bagryanskaya, Irina Yu.,Froehlich, Roland,Haufe, Guenter
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- Synthesis of (E)-stilbenes and (E,E)-1,4-diphenylbuta-1,3-diene promoted by boron trifluoride-diethyl ether complex
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An efficient, simple, and practical method has been de-veloped to regioselectively synthesize (E)-stilbenes and (E,E)-1,4diphenylbuta-1,3-diene in good to excellent yields in the presence of boron trifluoride-diethyl ether complex as a catalyst in a short reaction (30-60 s) at room temperature. Georg Thieme Verlag Stuttgart.
- Narender,Papi Reddy,Madhur
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- Utilization of microwave heating in the McMurry reaction for facile coupling of aldehydes and ketones to give alkenes
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Microwave heating was applied in high-yield syntheses of alkenes by McMurry coupling of aldehydes and ketones with low-valent titanium. All aldehydes and ketones including sulfur end-capped analogues gave alkenes in isolated yields above 80% without detectable amounts of pinacols.
- Stuhr-Hansen, Nicolai
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Read Online
- Reaction of tribenzylphosphine oxide with aldehydes
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Tribenzylphosphine oxide readily and stereoselectively reacts with aliphatic, aromatic, and heteroaromatic aldehydes in the presence of strong bases yielding exclusively (or predominantly) E-isomers of 1-organyl-2-phenylethenes and dibenzylphosphinic acid
- Gusarova,Ivanova,Reutskaya,Arbuzova,Baikalova,Deryagina,Russavskaya,Trofimov
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Read Online
- Heterobimetallic Pd/Mn and Pd/Co complexes as efficient and stereoselective catalysts for sequential Cu-free Sonogashira coupling–alkyne semi-hydrogenation reactions
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A series of heterobimetallic PdII/MII complexes (MII = Mn, Co) were synthesised and tested as precatalysts for sequential Sonogashira coupling–alkyne semi-hydrogenation reactions to form Z-aryl alkenes. The carbometalated heterobimetallic PdII/CoII complex CoPdL3′ demonstrated an apparent cooperative effect compared to the corresponding monometallic counterparts. This compound was identified as a potent single-molecule catalyst for the one-pot Cu-free Sonogashira coupling of aryl bromides with terminal alkynes followed by chemo- and stereoselective semi-hydrogenation of the alkyne intermediate using NH3·BH3 as a hydrogen source. Furthermore, different aromatic substrates have been tested to show the generality of the reaction for the synthesis of Z-alkenes, including biologically active combretastatin A-4. In addition, the homogeneous nature of the catalytically active species was demonstrated.
- Baweja, Saral,Clauss, Reike,Gelman, Dmitri,Hey-Hawkins, Evamarie
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p. 1344 - 1356
(2022/02/03)
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- Palladium Nanoparticles Anchored on Magnesium Organosilicate: An Effective and Selective Catalyst for the Heck Reaction
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A new and effective palladium catalyst supported on a magnesium organosilicate for application in the Heck reaction is presented. A group of compounds comprising 22 examples were synthesized in moderate to high yields (up to 99%) within a short time. The palladium supported on magnesium organosilicate catalyst was characterized as an amorphous solid by SEM, containing around 33% of palladium inside the solid, and even with this low quantity of palladium, the catalyst was very efficient in the Heck reaction. Besides, based on the Scherrer equation, the crystallite size of the synthesized palladium nanoparticles was ultrasmall (around 1.3 nm). This strategy is a simple and efficient route for the formation of C-C bonds via the Heck cross-coupling reaction.
- Dos Santos, Beatriz F.,Da Silva, Beatriz A. L.,De Oliveira, Aline R.,Sarragiotto, Maria H.,Rinaldi, Andrelson W.,Domingues, Nelson Luís C.
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supporting information
p. 1301 - 1306
(2020/11/04)
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- Immobilized Pd on a NHC-functionalized metal-organic FrameworkMIL-101(Cr): An efficient heterogeneous catalyst in the heck and copper-free Sonogashira coupling reactions
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A heterogeneous palladium catalyst system based on immobilization of palladium moieties on a N-heterocyclic carbene (NHC) modified metal organic framework (MOF) was developed for the Heck and copper-free Sonogashira coupling reactions. In order to prepare this catalyst system, first, MIL-101(Cr) was functionalized with NHC moieties through a post synthetic modification (PSM) approach, and then Pd metal was stabilized on the prepered MIL-101(Cr)-NHC substrate. This material was characterized using various microscopic and spectroscopic techniques and then was used as an efficient heterogeneous Pd catalyst system in the Heck and copper-free Sonogashira reactions. Results of the heterogeneity tests showed that the Pd-NHC-MIL-101(Cr) catalyst can efficiently catalyzed these coupling reactions heterogeneously and no remarkable changes observed in the morphology and structure of MIL-101(Cr) template during the reaction progress. Also, existence of palladium nanoparticles immobilized on the MOF structure affirmed by the TEM and XPS analysis confirmed the oxidation state of Pd. A variety of alkene and alkyne derivatives were synthesized in good to excellent yields using this heterogeneous Pd catalyst system under normal conditions. More importantly Pd-NHC-MIL-101(Cr) catalyst was simply recovered from the reaction medium without remarkable decreasing in its catalytic activities after five times of reusability. The ICP analysis showed the very low Pd and Cr metals leaching, representing high stability and applicability of this catalyst in Pd coupling reactions.
- Niknam, Esmaeil,Panahi, Farhad,Khalafi-Nezhad, Ali
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supporting information
(2021/01/12)
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- Pd supported on clicked cellulose-modified magnetite-graphene oxide nanocomposite for C-C coupling reactions in deep eutectic solvent
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Cellulose-modified magnetite-graphene oxide nanocomposite was prepared via click reaction and utilized for immobilization of palladium (Pd) nanoparticles without using additional reducing agent. The abundant OH groups of cellulose provided the uniform dispersion and high stability of Pd nanoparticles, while magnetite-graphene oxide as a supporting material offered high specific surface area and easy magnetic separation. The as-prepared nanocomposite served as a heterogeneous catalyst for the Heck and Sonogashira coupling reactions in various hydrophilic and hydrophobic deep eutectic solvents (DESs) as sustainable and environmentally benign reaction media. Among the fifteen DESs evaluated for coupling reactions, the hydrophilic DES composed of dimethyl ammonium chloride and glycerol exhibited the best results. Due to the low miscibility of catalyst and DES in organic solvents, the separated aqueous phase containing both of the catalyst and DES can be readily recovered by evaporating water and retrieved eight times with negligible loss of catalytic performance.
- Karimi, Sabah,Masteri-Farahani, Majid,Niakan, Mahsa,Shekaari, Hemayat
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- Efficient photocatalytic chemoselective and stereoselective C-C bond formation over AuPd@N-rich carbon nitride
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Heterogeneous chemoselective or stereoselective C-C coupling reactions remain extremely challenging in traditional organic synthesis. Here, we constructed a AuPd@N-rich carbon nitride (NRCN) photocatalyst through simple ammonia solution heat treatment of carbon nitride and then AuPd NP loading. AuPd@NRCN exhibited extraordinary light color promoted catalytic performance in C-C bond formation under visible light in air. Surprisingly, both high chemoselectivity to unsymmetrical Ullmann biaryl products and satisfactory stereoselectivity to Z-type Heck reaction products could be achieved by changing the light source color. Various substrates exhibited great potential for the economical synthesis of unsymmetrical biaryl products and Z-type olefins. Efficient visible light promoted C-I bond activation accompanied with improved photocatalytic coupling reaction efficiency over AuPd@NRCN was verified firstly by in situ DRIFTS. Considering that the Ullmann cross-coupling reaction is a multi-photon reaction, the improved photocatalytic performance in the Ullmann cross-coupling reaction using a combination of light sources with different colors might be due to the activation of different substrates and/or steps requiring different energies, and the combination of the two energy sources was beneficial for improving the activation efficiency of different substrates and/or steps. The activation of iodobenzene and styrene in the Heck reaction with light was also beneficial to the formation of the stilbene product. The light color promoted chemoselectivity and stereoselectivity are expected to have profound impact on organic synthetic methodology improvement. This journal is
- Jiang, Heyan,Xu, Jie,Zhang, Sishi,Cheng, Hongmei,Zang, Cuicui,Bian, Fengxia
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p. 219 - 229
(2021/01/28)
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- Synthesis of new adamantyl-imine palladium(II) complexes and their application in Mizoroki-Heck and Suzuki-Miyaura C[sbnd]C cross-coupling reactions
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Improving carbon–carbon cross-coupling reactions is an ongoing process and finding the most versatile and stable catalyst precursors has been of great interest. Ligand design has been proven to be important since it is responsible for providing electron density and steric saturation around the metal centre, thus contributing towards the stereo-electronic properties. The adamantyl moiety has been used to generate highly bulky and electron-rich ligands for application in palladium-catalysed cross-coupling reactions. Accordingly, we have prepared some Schiff-base adamantyl ligands (L1-L3) and complexed them with [PdCl2(MeCN)2] to afford the (pre)catalysts C1-C3, which were successfully applied in Mizoroki-Heck and Suzuki-Miyaura carbon–carbon cross-coupling reactions. The cross-coupling reaction products were obtained in good yields using 0.5 mol % Pd catalyst loading. C2 and C3 showed remarkable activity in the Mizoroki-Heck coupling reactions involving substrates with substituents on the olefin and aryl halide (including 4-Cl, 4-CH3, -CO2Me and -CO2Et). We also, observed that the Suzuki-Miyaura cross-coupling system was active towards challenging activated and deactivated aryl chlorides, with to up 70% conversions recorded. The mercury poisoning tests conducted revealed that the catalysts act as homogenous molecular active species in the Mizoroki-Heck reactions and act as both homogenous and heterogeneous catalysts in the Suzuki-Miyaura cross-coupling reactions.
- Makhubela, Banothile C. E.,Matsheku, Asanda C.,Maumela, Munaka C.
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- Dinuclear cobalt complex-catalyzed stereodivergent semireduction of alkynes: Switchable selectivities controlled by H2O
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Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multichemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z-E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.
- Chen, Ke,Zhu, Hongdan,Li, Yuling,Peng, Qian,Guo, Yinlong,Wang, Xiaoming
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p. 13696 - 13705
(2021/11/16)
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- Method for selectively synthesizing cis-trans-olefin by catalytic alkyne semi-reduction through water-hydrogen-supplying palladium
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The method comprises the following steps: TEOA, NaOAc, a catalyst, water and alkyne are subjected to a reduction reaction of alkyne in an organic solvent to react to form cis-olefin. Ligand t-Bu2 PCl, The catalyst, water and the alkyne are subjected to a reduction reaction of alkyne in an organic solvent to react to form a trans-olefin. The reactor for the reduction reaction is a sealed pressure-resistant reactor, the temperature of the reduction reaction is 120 - 150 °C, and the reduction reaction time is 20 - 40h. The amount of the catalyst used is 5 - 20% of the molar amount of alkyne, and the amount of water is 10 - 50 times of the molar amount of alkyne. The ligand is used in an amount 2-5 times the molar amount of catalyst. In the invention, the catalyst system has extremely high chemical reaction and stereoselectivity, and cis or trans olefinic products can be synthesized at high yield. The catalytic system has strong universality on substrates, and alkynes containing various functional groups can efficiently carry out high-selectivity reduction reaction.
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Paragraph 0098; 0109-0112
(2021/10/30)
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- Water-hydrogen-supplying iridium catalytic alkyne semi-reduction selective synthesis method Process for trans-olefines
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The method comprises the following steps: DPPE, COD, a catalyst, water and alkyne are subjected to reduction reaction of alkyne in an organic solvent, and cis-olefin is generated by reaction under nitrogen protection. The ligand DPPE, the catalyst, the water and the alkyne are subjected to a reduction reaction of alkyne in an organic solvent, and a trans-olefin is generated by the reaction under nitrogen protection. The reactor for the reduction reaction is a sealed pressure-resistant reactor, the temperature of the reduction reaction is 100 - 130 °C, and the reduction reaction time is 20 - 48h. The amount of the catalyst used is 5 - 20% of the molar amount of alkyne, and the amount of water is 10 - 50 times of the molar amount of alkyne. The ligand is used in an amount 0.2 - 5 times the molar amount of catalyst. The catalyst system disclosed by the invention has extremely high chemical reaction and stereoselectivity, and cis or trans olefinic products can be synthesized at high yield. The catalytic system has strong universality on substrates, and alkynes containing various functional groups can efficiently carry out high-selectivity reduction reaction.
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Paragraph 0102-0105
(2021/09/29)
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- Method for reducing alkyne into olefin by taking water as hydrogen source under catalysis of nickel
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The invention discloses a method for reducing alkyne into olefin by taking water as a hydrogen source under the catalysis of nickel, which comprises the following steps: placing alkyne in a solvent to react under the action of a nickel catalyst, a ligand, alkali, a boron reagent and a hydrogen source, and carrying out post-treatment to obtain olefin, and the hydrogen source is water. According to the invention, a cheap metal nickel catalyst is combined with a boron reagent to activate water, so that hydrogen transfer is realized, and the use of dangerous hydrogen is avoided. The method has good stereoselectivity, no excessive hydrogenation product alkane is generated, conditions are mild, the highest yield can reach 99%, and the method has good application prospects.
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Paragraph 0059-0062
(2021/06/26)
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- Ruthenium-Catalyzed E-Selective Partial Hydrogenation of Alkynes under Transfer-Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source
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E-alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium-catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer-hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer-hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p-cymene)Cl2]2 complex as pre-catalyst in combination with 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E-selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well-known Z-selective Lindlar reduction in late-stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2-paraformaldehyde and D2O mixtures.
- Fetzer, Marcus N. A.,Tavakoli, Ghazal,Klein, Axel,Prechtl, Martin H. G.
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p. 1317 - 1325
(2021/02/11)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Nickel-Catalyzed Enantioselective α-Alkenylation of N-Sulfonyl Amines: Modular Access to Chiral α-Branched Amines
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Chiral α-branched amines are common structural motifs in functional materials, pharmaceuticals, and chiral catalysts. Therefore, developing efficient methods for preparing compounds with these privileged scaffolds is an important endeavor in synthetic chemistry. Herein, we describe an atom-economical, modular method for a nickel-catalyzed enantioselective α-Alkenylation of readily available linear N-sulfonyl amines with alkynes to afford a wide variety of allylic amines without the need for exogenous oxidants, reductants, or activating reagents. The method provides a platform for constructing chiral α-branched amines as well as derivatives such as α-Amino amides and β-Amino alcohols, which can be conveniently accessed from the newly introduced alkene. Given the generality, versatility, and high atom economy of this method, we anticipate that it will have broad synthetic utility.
- Li, Lun,Liu, Yu-Cheng,Shi, Hang
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supporting information
p. 4154 - 4161
(2021/04/06)
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- Efficient preparation method of symmetric diarylethene compound
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The invention belongs to the technical field of fine chemicals and related chemistry, and provides an efficient preparation method of a symmetric diarylethene compound. The method comprises the following steps: with halomethyl-containing aromatic hydrocarbon and derivatives thereof as raw materials, conducting reacting at 100 DEG C for 12 hours in the presence of a catalyst, alkali, additives andan anhydrous organic solvent so as to obtain the corresponding diarylethene compound with symmetry. The method has the beneficial effects that no transition metal reaction exists, reaction conditionsare mild, operation is simple and convenient, the possibility of industrialization is realized, and the diarylethene compound is obtained at high yield; and the diarylethene compound synthesized by using the method can be further functionalized to obtain various compounds, and is applied to development and research of natural products, functional materials and fine chemicals.
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Paragraph 0047-0049
(2021/02/10)
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- Aza-peterson olefinations: Rapid synthesis of (E)-alkenes
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An aza-Peterson olefination methodology to access 1,3-dienes and stilbene derivatives from the corresponding allyl- or benzyltrimethylsilane is described. Silanes can be deprotonated using Schlosser's base and added to N -phenyl imines or ketones to directly give the desired products in high yields.
- Britten, Thomas K.,Basson, Ashley J.,Roberts, Dean D.,McLaughlin, Mark G.
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p. 3535 - 3544
(2021/06/03)
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- Visible-light-induced oxidative coupling of vinylarenes with diselenides leading to α-aryl and α-alkyl selenomethyl ketones
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A visible-light-induced oxidative coupling of diselenides with readily available vinylarenes is demonstrated. This benign protocol allows one to access a wide range of α-aryl and α-alkyl selenomethyl ketones in good yields with excellent functional group compatibility. The distinct advantages of this protocol over all previous methods include the use of a green solvent and air as an oxidant and the lack of a photocatalyst, a base, and an oxidant as well as better green chemistry matrices. Furthermore, the title reaction can be performed with natural sunlight, the most sustainable energy source imaginable. Additionally, the mild reaction conditions, easy operation and suitability for the modification of styrene-functionalized biomolecules make the current reaction system a more attractive method for the synthesis of a variety of medicinal and agrochemical compounds of interest.
- Liu, Gong-Qing,Yi, Wei,Wang, Peng-Fei,Liu, Ji,Ma, Meng,Hao, Da-Yun,Ming, Liang,Ling, Yong
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supporting information
p. 1840 - 1846
(2021/03/09)
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- Catalytic Hydrogenation of Alkenes and Alkynes by a Cobalt Pincer Complex: Evidence of Roles for Both Co(I) and Co(II)
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The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E- and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe3)(CyPNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH(CyPNP)], can also be generated by treatment of degassed solutions of [Co(N2)(CyPNP)] with H2. The CoII-hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.
- Alawisi, Hussah,Arman, Hadi D.,Tonzetich, Zachary J.
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p. 1062 - 1070
(2021/04/09)
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- Mild and efficient desulfurization of thiiranes with MoCl5/Zn system
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Desulfurization of a variety of thiiranes to alkenes occurs chemoselectively in high yields upon treatment with MoCl5/Zn system under mild conditions. The new methodology demonstrates high functional group tolerance toward chloro, bromo, fluoro, methoxy, ester, ether and keto groups.
- Lee, Yeong Jin,Shin, Jeong Won,Yoo, Byung Woo
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- Selective Palladium-Catalyzed α,β-Homodiarylation of Vinyl Esters in Aqueous Medium
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A palladium-catalyzed 1,2-diarylation of vinyl esters with arylboronic acids in water has been developed. This newly elaborated protocol features a good functional group tolerance and provides one-step access to 1,2-diarylethanol derivatives under mild reaction conditions. The presented reaction can be carried out in the water at ambient temperature without the addition of any ligands, what makes this procedure environmentally benign. The transformation occurs within a single catalytic cycle and is feasible due to the modification of transition metal catalytic activity through the influence of π-acceptor olefin (benzoquinone) as well as water as a medium. Moreover, this protocol allows to generate entire compound libraries (highly profitable in medicinal chemistry) and utilizes sustainable arylboronic acids as coupling partners under mild conditions. It is also noted that the structure of boron moiety has a great impact on the reaction selectivity, the usage of sterically hindered esters of arylboronic acids influence the reaction course towards stilbenes.
- Brodzka, Anna,Koszelewski, Dominik,Ostaszewski, Ryszard,Trzepizur, Damian,Wilk, Monika
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supporting information
p. 6028 - 6036
(2021/12/10)
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- A Colorimetric Method for Quantifying Cis and Trans Alkenes Using an Indicator Displacement Assay
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A colorimetric indicator displacement assay (IDA) amenable to high-throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96-well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn- or anti-addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.
- Valenzuela, Stephanie A.,Crory, Hannah S. N.,Yao, Chao-Yi,Howard, James R.,Saucedo, Gabriel,de Silva, A. Prasanna,Anslyn, Eric V.
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supporting information
p. 13819 - 13823
(2021/05/17)
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- Palladium Complexes with Phenoxy- And Amidate-Functionalized N-Heterocyclic Carbene Ligands Based on 3-Phenylimidazo[1,5- a]pyridine: Synthesis and Catalytic Application in Mizoroki-Heck Coupling Reactions with Ortho-Substituted Aryl Chlorides
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Mononuclear and tetranuclear palladium complexes with functionalized "abnormal"N-heterocyclic carbene (aNHC) ligands based on 3-phenylimidazo[1,5-a]pyridine were synthesized. All of the new complexes were structurally characterized by single-crystal X-ray diffraction studies. The new complexes were applied in the Mizoroki-Heck coupling reaction of aryl chlorides with alkenes in neat n-tetrabutylammonium bromide (TBAB). The mononuclear palladium complex with a tridentate phenoxy- and amidate-functionalized aNHC ligand displayed activity superior to that of the palladium complex with a bidentate amidate-functionalized aNHC ligand. The new tetranuclear complex with the tridentate ligand displayed the best activities, capable of the activation of deactivated aryl chlorides as substrates with a low Pd atom loading. Even challenging sterically demanding ortho-substituted aryl chlorides were successfully utilized as substrates. The studies revealed that the robustness of the catalyst precursor is crucial in delivering high catalytic activities. Also, the promising use of tetranuclear palladium complexes with functionalized aNHC ligands as the catalyst precursors in the Mizoroki-Heck coupling reaction in neat TBAB was demonstrated.
- Hung, Cheng-Hau,Zheng, Wei-Yuan,Lee, Hon Man
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p. 702 - 713
(2021/04/02)
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- Palladium Loaded Dendronized Polymer as Efficient Polymeric Sustainable Catalyst for Heck Coupling Reaction
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The palladium incorporated amine-functionalized dendronized polymer was synthesized by the addition of palladium acetate to dendronized polymer in methanol at room temperature. Palladium species are immobilized onto the dendritic structure by their coordination with amino functional groups. The newly developed dendritic system showed high palladium content in the low generation level itself, which was found to be 4.19?mmol/g. This was fairly higher than, the other palladium-based catalysts. Energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, UV–Visible spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the successful synthesis of the new catalyst. It was used as a homogeneous palladium catalyst for Heck coupling reaction between olefins and differently substituted aryl halides and the products were isolated in high yield. The products isolated were in trans configuration, which indicated the selectivity of the newly developed catalytic system. Also, this catalyst system was reused up to nine times without a significant decrease in its catalytic activity. The easy accessibility of catalytic sites, stability, resistance to metal leaching, high catalytic activity and remarkable stereoselectivity with a low amount of catalyst are all due to the dendritic support. The docking study was carried out for all the stilbene derivatives obtained by the Heck coupling reaction against DprE1 protein to study its potential antitubercular activity. All the compounds displayed superior docking score values over the range ??6.5 to ??8.2?kcal/mol, compared to the standard drug isoniazid with docking score of ??6.1?kcal/mol against DprE1. Graphic Abstract: [Figure not available: see fulltext.]
- Hiba, K.,Krishna, G. Anjali,Prathapan, S.,Sreekumar, K.
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- Fe-MIL-101 modified by isatin-Schiff-base-Co: a heterogeneous catalyst for C-C, C-O, C-N, and C-P cross coupling reactions
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A metal-organic framework functionalized with a cobalt-complex is preparedviapost-synthetic modification of Fe-MIL-101-NH2. Initially, Fe-MIL-101-NH2reacted with isatin to produce Fe-MIL-101-isatin-Schiff-base, which can anchor the cobalt by the addition of cobalt acetate. The resulting MOF-Co catalyst is characterized by employing multiple techniques. This new modified MOF acts as a heterogeneous and recyclable catalyst for efficient Ullmann, Buchwald-Hartwig, Hirao, Hiyama and Mizoroki-Heck cross-coupling reactions of several aryl halides/phenylboronic acid/phenyltosylate with phenols, anilines/heterocyclic amines, triethyl phosphite, triethoxyphenylsilane and alkenes and generates the expected coupling products in good to high yields.
- Farrokhi, Alireza,Rouzifar, Majid,Sansano, José Miguel,Sobhani, Sara
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p. 19963 - 19976
(2021/11/12)
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- Recyclable heterogeneous iron supported on imidazolium ionic liquid catalysed palladium and copper-free Heck reaction
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A natural friendly iron-immobilized on imidazolium supported ionic liquid [Gmim]Cl-Fe (III) was effectively evaluated as a heterogeneous catalyst for Mizoroki-Heck reaction with good to excellent yield under solvent free condition. [Gmim]Cl-Fe (III) showed good activities that were comparable to that of palladium catalysts. Furthermore, this phosphine, copper and palladium- free catalyst was simply recovered from the reaction mixture and recycled seven times.
- Deepa, Manickam,Kalaivani, Kolanjinathan,Parasuraman, Karthikeyan,Selvarasu, Uthayanila
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- Immobilizing palladium on melamine-functionalized magnetic nanoparticles: An efficient and reusable phosphine-free catalyst for Mizoroki–Heck reaction
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A highly efficient and stable heterogeneous catalyst was successfully prepared by anchoring palladium(0) onto melamine-functionalized Fe3O4 magnetic nanoparticles (MNPs-Mel-Pd). With the aid of amine functional groups, melamine was covalently bonded on epoxy functionalized magnetic nanoparticles and then Pd(0) was immobilized on this support with high dispersion. The prepared nanocatalyst exhibits excellent catalytic activity for C-C cross coupling (Mizoroki–Heck) of various aryl halides (iodide, bromides, and chrlorides) with olefins under mild reaction condition in relatively short reaction times. The synthesized nanocatalyst was characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS) techniques. The loading level of Pd in MNPs-Mel-Pd catalyst was measured to be 1.26 × 10?3 mol g?1 by atomic absorption spectroscopy (AAS). In addition, the catalyst can be easily separated and recovered from the reaction mixture by using an external magnet. The heterogeneity of the catalyst was confirmed by the hot filtration test, which was reused for at least six times under the optimized conditions without any significant loss of its activity.
- Aryanasab, Fezzeh,Shabanian, Meisam,Laoutid, Fouad,Vahabi, Henri
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- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
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The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
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p. 312 - 318
(2021/01/29)
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- Transition-Metal-Free Matsuda-Heck Type Cross-Coupling and Mechanistic Evidence for a Radical Mechanism
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The Matsuda-Heck reaction, usually performed with palladium catalysts, can be carried out under transition-metal-free conditions in the presence of a KOtBu/DMF couple. This system allows the selective and direct synthesis of stilbenes from aryldiazonium salts under mild temperature (20 °C). Mechanistic studies suggest a radical pathway in which the DMF acts as the initiator of the overall process.
- Bergès, Julien,Zaid, Yassir,Tlili, Anis,Sotiropoulos, Jean-Marc,Taillefer, Marc
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supporting information
p. 1559 - 1563
(2021/02/27)
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- Cobalt Complexes of Bulky PNP Ligand: H2Activation and Catalytic Two-Electron Reactivity in Hydrogenation of Alkenes and Alkynes
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The reactivity of cobalt pincer complexes supported by the bulky tetramethylated PNP ligands Me4PNPR(R = iPr, tBu) has been investigated. In these ligands, the undesired H atom loss reactivity observed earlier in some classical CH2-arm PNP cobalt complexes is blocked, allowing them to be utilized for promoting two-electron catalytic transformations at the cobalt center. Accordingly, reaction of the formally CoIMe complex 3 with H2 under ambient pressure and temperature afforded the CoIII trihydride 4-H, in a reaction cascade reasoned to proceed by two-electron oxidative addition and reductive eliminations. This mechanistic proposal, alongside the observance of alkene insertion and ethane production upon sequential exposure of 3 to ethylene and H2, prompted an exploration into 3 as a catalyst for hydrogenation. Complex 4-H, formed in situ from 3 under H2, was found to be active in the catalytic hydrogenation of alkenes and alkynes. The proposed two-electron mechanism is reminiscent of the platinum group metals and demonstrates the utility of the bulky redox-innocent Me4PNPR ligand in the avoidance of one-electron reactivity, a concept that may show broad applicability in expanding the scope of earth-abundant first-row transition-metal catalysis.
- Fayzullin, Robert R.,Gallagher, James M.,Khaskin, Eugene,Khusnutdinova, Julia R.,Lapointe, Sébastien,Osborne, James,Pandey, Dilip K.
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supporting information
p. 3617 - 3626
(2021/11/16)
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- Visible light enables catalytic formation of weak chemical bonds with molecular hydrogen
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The synthesis of weak chemical bonds at or near thermodynamic potential is a fundamental challenge in chemistry, with applications ranging from catalysis to biology to energy science. Proton-coupled electron transfer using molecular hydrogen is an attractive strategy for synthesizing weak element–hydrogen bonds, but the intrinsic thermodynamics presents a challenge for reactivity. Here we describe the direct photocatalytic synthesis of extremely weak element–hydrogen bonds of metal amido and metal imido complexes, as well as organic compounds with bond dissociation free energies as low as 31 kcal mol?1. Key to this approach is the bifunctional behaviour of the chromophoric iridium hydride photocatalyst. Activation of molecular hydrogen occurs in the ground state and the resulting iridium hydride harvests visible light to enable spontaneous formation of weak chemical bonds near thermodynamic potential with no by-products. Photophysical and mechanistic studies corroborate radical-based reaction pathways and highlight the uniqueness of this photodriven approach in promoting new catalytic chemistry. [Figure not available: see fulltext.].
- Park, Yoonsu,Kim, Sangmin,Tian, Lei,Zhong, Hongyu,Scholes, Gregory D.,Chirik, Paul J.
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p. 969 - 976
(2021/07/25)
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- N-Heterocyclic carbene palladium (II)-pyridine (NHC-Pd (II)-Py) complex catalyzed heck reactions
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A mild, efficient, and practical catalytic system for the synthesis of highly privileged stilbene pharmacophores is reported. This system uses N-heterocyclic carbene palladium (II) Pyridine (NHC-Pd (II)-Py) complex to catalyze the formation of carbon-carbon bonds between olefin derivatives and various bromide. This simple, gentle and user-friendly method can offer a variety of stilbene products in excellent yields under solvent-free condition. And its scale-up reaction has excellent yield and this system can be applied to industrial fields. The utility of this method is highlighted by its universality and modular synthesis of a series of bioactive molecules or important medical intermediates.
- Li, Dan,Tian, Qingqiang,Wang, Xuetong,Wang, Qiang,Wang, Yin,Liao, Siwei,Xu, Ping,Huang, Xin,Yuan, Jianyong
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supporting information
p. 2041 - 2052
(2021/05/25)
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- Manganese-catalysed divergent silylation of alkenes
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Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale. [Figure not available: see fulltext.].
- Dong, Jie,Yuan, Xiang-Ai,Yan, Zhongfei,Mu, Liying,Ma, Junyang,Zhu, Chengjian,Xie, Jin
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p. 182 - 190
(2020/12/17)
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- Wittig Olefination Using Phosphonium Ion-Pair Reagents Incorporating an Endogenous Base
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Despite common perception, the use of strong bases in Wittig chemistry is utterly unnecessary: we report a series of novel ion-pair phosphonium carboxylate reagents which are essentially "storable ylides". These reagents are straightforwardly prepared in excellent yields, and their fluxional nature permits clean olefination of a broad range of aldehydes and even hemiacetals.
- Vetter, Anna C.,Gilheany, Declan G.,Nikitin, Kirill
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p. 1457 - 1462
(2021/03/08)
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- Palladium nanoparticlesin situsynthesized onCyclea barbatapectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes
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This study develops an effective method for thein situsynthesis of palladium nanoparticles (PdNPs) usingCyclea barbatapectin as a green reducing and stabilizing reagent. The PdNP@pectin nanocomposite was well characterized by analysis techniques such as UV-vis, FTIR, EDX, XRD, SEM, HR-TEM and STEM-mapping. Crystalline PdNPs were found to be distributed in the size range of 1-25 nm with the highest frequency of 6-12 nm. PdNP@pectin exhibited excellent recyclable catalysis activity for the Heck coupling reaction in water medium. The kinetics and recyclability of nanoparticles were investigated for the catalytic reduction ofo-,m- andp-nitrophenol. The result showed a good catalysis efficiency with five successful recycles without compromising much. In particular, the nanocomposite was used as a catalyst for the conversion of alkynes intocis-alkenes with KOH/DMF as a hydrogenation source. The reaction was also utilized effectively for the synthesis of sex pheromones, includingPlutella xylostella((Z)-11-hexadecen-1-yl acetate) andCylas formicarius((Z)-3-dodecen-1-yl(E)-2-butenoate) with the total yields of 70% and 68%, respectively. Therefore, PdNPs supported onC. barbatapectin are promising catalysis materials for application in various fields.
- Le, Van-Dung,Le, T. Cam-Huong,Chau, Van-Trung,Le, T. Ngoc-Duyen,Dang, Chi-Hien,Vo, T. To-Nguyen,Nguyen, Trinh Duy,Nguyen, Thanh-Danh
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p. 4746 - 4755
(2021/03/22)
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- Copper-Photocatalyzed Hydrosilylation of Alkynes and Alkenes under Continuous Flow
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Herein, the photocatalytic hydrosilylation of alkynes and alkenes under continuous flow conditions is described. By using 0.2 mol % of the developed [Cu(dmp)(XantphosTEPD)]PF6 under blue LEDs irradiation, a large panel of alkenes and alkynes was hydrosilylated in good to excellent yields with a large functional group tolerance. The mechanism of the reaction was studied, and a plausible scenario was suggested.
- Zhong, Mingbing,Pannecoucke, Xavier,Jubault, Philippe,Poisson, Thomas
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p. 11818 - 11822
(2021/07/10)
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- Electro-mediated PhotoRedox Catalysis for Selective C(sp3)–O Cleavages of Phosphinated Alcohols to Carbanions
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We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp3)?O bonds of phosphinated alcohols to alkyl carbanions. As well as deoxygenations, olefinations are reported which are E-selective and can be made Z-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation, and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for an intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp3)?O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions tolerate aryl chlorides/bromides and do not give rise to Birch-type reductions.
- Barham, Joshua P.,K?nig, Burkhard,Karl, Tobias A.,Reiter, Sebastian,Tian, Xianhai,Yakubov, Shahboz,de Vivie-Riedle, Regina
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p. 20817 - 20825
(2021/08/18)
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- Selective Construction of C?C and C=C Bonds by Manganese Catalyzed Coupling of Alcohols with Phosphorus Ylides
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Herein, we report the manganese catalyzed coupling of alcohols with phosphorus ylides. The selectivity in the coupling of primary alcohols with phosphorus ylides to form carbon-carbon single (C?C) and carbon-carbon double (C=C) bonds can be controlled by the ligands. In the conversion of more challenging secondary alcohols with phosphorus ylides the selectivity towards the formation of C?C vs. C=C bonds can be controlled by the reaction conditions, namely the amount of base. The scope and limitations of the coupling reactions were thoroughly evaluated by the conversion of 21 alcohols and 15 ylides. Notably, compared to existing methods, which are based on precious metal complexes as catalysts, the present catalytic system is based on earth abundant manganese catalysts. The reaction can also be performed in a sequential one-pot reaction generating the phosphorus ylide in situ followed manganese catalyzed C?C and C=C bond formation. Mechanistic studies suggest that the C?C bond was generated via a borrowing hydrogen pathway and the C=C bond formation followed an acceptorless dehydrogenative coupling pathway. (Figure presented.).
- Liu, Xin,Werner, Thomas
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supporting information
p. 1096 - 1104
(2020/12/31)
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- A Solid-Phase Assisted Flow Approach to In Situ Wittig-Type Olefination Coupling
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Described herein is the development of a continuous flow, solid-phase triphenylphosphine (PS-PPh3) assisted protocol to facilitate the in situ coupling of reciprocal pairs of halogen and carbonyl functionalised molecular pairs by a Wittig olefination within 15 mins. The protocol entails injecting a single solution (1 : 1 CHCl3 : EtOH) containing the halogenated and carbonyl-based substrates into a continuously flowing stream of CHCl3 : EtOH (1 : 1), passed through a fixed bed of K2CO3 and PS-PPh3. With advancement to the previous PS-PPh3 coupling procedures, the method employs a traditional polystyrene-based immobilisation matrix, the substrate scope of the protocol extended to substituted ketones, secondary alkyl chlorides, and an unprotected maleimide scaffold.
- Aldrich-Wright, Janice R.,Dankers, Christian,Gordon, Christopher P.,Polyzos, Anastasios,Tadros, Joseph
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supporting information
p. 4184 - 4194
(2021/08/24)
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- Olefin Metathesis, p-Cresol, and the Second Generation Grubbs Catalyst: Fitting the Pieces
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p-Cresol as additive to the Grubbs second generation catalyst (GII) allows the cross-metathesis of acrylates with prop-1-en-1-ylbenzenes under conditions that only give the prop-1-en-1-ylbenzene self-metathesis product in the absence of cresol. NMR and IR spectroscopy, MALDI-TOF MS and XPS supported the formation of a ruthenium benzylidene with hydrogen bonds between p-cresol and the chloride ligands of GII. XPS furthermore confirmed p-cresol to increase the binding energies of the GII Ru 3d5/2, 3d3/2, 3p3/2 and 3p1/2 photoelectron lines, whereas 1H NMR spectroscopy indicated the carbene carbon and hydrogen to be shielded. It is thus postulated that p-cresol allows for more facile interaction between electron-deficient compounds and the ruthenium benzylidene by decreasing the electron density on the metal center and increasing the electron density on the carbene.
- Swart, Marthinus R.,Twigge, Linette,Erasmus, Elizabeth,Marais, Charlene,Bezuidenhoudt, Barend C. B.
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supporting information
p. 1752 - 1762
(2021/05/06)
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- Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
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Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
- Iakovenko, Roman,Hlavá?, Jan
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p. 440 - 446
(2021/01/28)
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- A donor-acceptor complex enables the synthesis of: E -olefins from alcohols, amines and carboxylic acids
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Olefins are prevalent substrates and functionalities. The synthesis of olefins from readily available starting materials such as alcohols, amines and carboxylic acids is of great significance to address the sustainability concerns in organic synthesis. Metallaphotoredox-catalyzed defunctionalizations were reported to achieve such transformations under mild conditions. However, all these valuable strategies require a transition metal catalyst, a ligand or an expensive photocatalyst, with the challenges of controlling the region- and stereoselectivities remaining. Herein, we present a fundamentally distinct strategy enabled by electron donor-acceptor (EDA) complexes, for the selective synthesis of olefins from these simple and easily available starting materials. The conversions took place via photoactivation of the EDA complexes of the activated substrates with alkali salts, followed by hydrogen atom elimination from in situ generated alkyl radicals. This method is operationally simple and straightforward and free of photocatalysts and transition-metals, and shows high regio- and stereoselectivities.
- Chen, Kun-Quan,Shen, Jie,Wang, Zhi-Xiang,Chen, Xiang-Yu
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p. 6684 - 6690
(2021/05/31)
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- 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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- Ligand-free (: Z)-selective transfer semihydrogenation of alkynes catalyzed by in situ generated oxidizable copper nanoparticles
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Herein, we present (Z)-selective transfer semihydrogenation of alkynes based on in situ generated CuNPs in the presence of hydrogen donors, such as ammonia-borane and a green protic solvent. This environmentally friendly method is characterized by operational simplicity combined with high stereo- and chemoselectivity and functional group compatibility. Auto-oxidation of CuNPs after the completion of a semihydrogenation reaction results in the formation of a water-soluble ammonia complex, so that the catalyst may be reused several times by simple phase-separation with no need for any special regeneration processes. Formed NH4B(OR)4 can be easily transformed back into ammonia-borane or into boric acid. In addition, a one-pot tandem sequence involving a Suzuki reaction followed by semihydrogenation was presented, which allows minimization of chemical waste production.
- Grela, Karol,Kusy, Rafa?
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p. 5494 - 5502
(2021/08/16)
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- Tandem Acceptorless Dehydrogenative Coupling-Decyanation under Nickel Catalysis
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The development of new catalytic processes based on abundantly available starting materials by cheap metals is always a fascinating task and marks an important transition in the chemical industry. Herein, a nickel-catalyzed acceptorless dehydrogenative coupling of alcohols with nitriles followed by decyanation of nitriles to access diversely substituted olefins is reported. This unprecedented C=C bond-forming methodology takes place in a tandem manner with the formation of formamide as a sole byproduct. The significant advantages of this strategy are the low-cost nickel catalyst, good functional group compatibility (ether, thioether, halo, cyano, ester, amino, N/O/S heterocycles; 43 examples), synthetic convenience, and high reaction selectivity and efficiency.
- Babu, Reshma,Balaraman, Ekambaram,Midya, Siba P.,Subaramanian, Murugan,Yadav, Vinita
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p. 7552 - 7562
(2021/06/28)
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- Single step production of styrene from benzene by alkenylation over palladium-anchored thermal defect rich graphitic carbon nitride catalyst
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Styrene is a widely used monomer in polymer industries for the manufacturing of plastics, rubbers and resins. The commercial styrene production process suffers from disadvantages such as requiring multiple steps, catalyst deactivation, high energy consump
- Avasthi, Kalpana,Bohre, Ashish,Jerman, Ivo,Kova?, Janez,Likozar, Bla?,Ter?an, Janvit
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- Custom-Made Pyrene Photocatalyst-Promoted Desulfonylation of Arylethenyl Sulfones Using Green-Light-Emitting Diodes
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The Sonogashira coupling of 1,3,6,8-tetrabromopyrene with 4-[(-)-β-citronellyloxy]phenylethyne was employed to synthesize 1,3,6,8-tetra[4-(citronellyloxy)phenylethynyl]pyrene. The pyrene derivative catalyzed the reductive desulfonylation of ethenyl sulfones via visible-light irradiation (514 nm green light-emitting diodes) in the presence of i -Pr 2NEt. The β-citronellyloxy groups provided the sufficient solubility to the highly π-expanded pyrene catalyst, and their polar oxygen functionalities enabled the easy separation of the catalyst from the products via column chromatography.
- Watanabe, Hikaru,Nakajima, Kazuki,Ekuni, Kento,Edagawa, Ryota,Akagi, Yuta,Okuda, Yasuhiro,Wakamatsu, Kan,Orita, Akihiro
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p. 2984 - 2994
(2021/03/04)
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- Ready approach to poly(vinyldiphenylphosphine): A novel soluble polymer for conveniently conducting Wittig reactions
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The novel poly(vinyldiphenylphosphine) could be easily prepared by using the reactions of the cheap poly(vinyl chloride) with sodium phosphides. Poly(vinyldiphenylphosphine) is soluble in common solvents while its corresponding phosphine oxide is hardly soluble in the solvents. Taking advantage of this different solubility, poly(vinyldiphenylphosphine) could be used as a soluble phosphinopolymer for the Wittig reactions. The reactions could take place efficiently to produce the corresponding olefins while the isolation of the products were simple since the resulted poly(vinyldiphenylphosphine oxide) was not soluble in the solvent and could be easily removed by filtration.
- Ye, Jing-Jing,Han, Li-Biao
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supporting information
(2021/01/25)
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- Photocatalyzed Transition-Metal-Free Oxidative Cross-Coupling Reactions of Tetraorganoborates**
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Readily accessible tetraorganoborate salts undergo selective coupling reactions under blue light irradiation in the presence of catalytic amounts of transition-metal-free acridinium photocatalysts to furnish unsymmetrical biaryls, heterobiaryls and arylated olefins. This represents an interesting conceptual approach to forge C?C bonds between aryl, heteroaryl and alkenyl groups under smooth photochemical conditions. Computational studies were conducted to investigate the mechanism of the transformation.
- Music, Arif,Baumann, Andreas N.,Boser, Florian,Müller, Nicolas,Matz, Florian,Jagau, Thomas C.,Didier, Dorian
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p. 4322 - 4326
(2021/02/11)
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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- Mizoroki-Heck Reaction of Unstrained Aryl Ketones via Ligand-Promoted C-C Bond Olefination
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Mizoroki-Heck reaction of unstrained aryl ketone with acrylate/styrene is accomplished via palladium-catalyzed ligand-promoted C-C bond cleavage. Various (hetero)aryl ketones are compatible in the reaction, affording the alkene product in good to excellent yields. Further applications in the late-stage olefination of some drugs, natural products, and fragrance-derived aryl ketones demonstrate the synthetic utility of this protocol. By employing ketone as both the directing group and the leaving group, 1,2-bifunctionalization is achieved via sequential ortho-C-H alkylation/ipso-Heck olefination.
- Wang, Mei-Ling,Xu, Hui,Li, Han-Yuan,Ma, Biao,Wang, Zhen-Yu,Wang, Xing,Dai, Hui-Xiong
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supporting information
p. 2147 - 2152
(2021/04/05)
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- B(C6F5)3-Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene Boranes via B—H Bond Activation
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In this work, a novel mode for the activation of N-heterocyclic carbene boranes (NHC-boranes) was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C6F5)3 in an frustrated Lewis pairs manner. A broad range of alkenes including stilbenes, β-methylstyrenes, styrenes, and alkyl-alkenes were suitable substrates for the B(C6F5)3-catalyzed hydroboration to furnish the desired products in good to high yields. Significantly, excellent regioselectivities were obtained in some cases. Mechanistic studies indicate that the B—H bond cleavage is likely involved in the rate-determining step. In addition, an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated. The current work provides a promising method for the activation of stable borane adducts, which might lead to some interesting transformations in the future.
- Wang, Qiaotian,Meng, Wei,Feng, Xiangqing,Du, Haifeng
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p. 918 - 926
(2021/04/09)
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