- N-Methylphenothiazine S-Oxide Enabled Oxidative C(sp2)–C(sp2) Coupling of Boronic Acids with Organolithiums via Phenothiaziniums
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Herein, we report the development of a transition-metal-free oxidative C(sp2)–C(sp2) coupling of readily available boronic acids and organolithiums via phenothiazinium ions. Various biaryl, styrene, and diene derivatives were obtained using this reaction system. The key to this process is N-methylphenothiazine S-oxide (PTZSO), which allows efficient conversion of boronic acids to phenothiazinium ions. The mechanism of phenothiazinium formation using PTZSO was investigated using theoretical calculations and experiments, which provided insight into the unique reactivity of PTZSO.
- Yoshida, Tatsuki,Honda, Yuki,Morofuji, Tatsuya,Kano, Naokazu
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p. 9664 - 9668
(2021/12/17)
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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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- 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; 0113-0116
(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 0106-0109
(2021/09/29)
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- Ligand-controlled iridium-catalyzed semihydrogenation of alkynes with ethanol: highly stereoselective synthesis of E- and Z-alkenes
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A ligand-controlled iridium-catalyzed semihydrogenation of alkynes to E- and Z-alkenes with ethanol was developed. Effective selectivity control was achieved by ligand regulation. The use of 1,2-bis(diphenylphosphino)ethane (DPPE) and 1,5-cyclooctadiene (COD) was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 40 alkenes, with good stereoselectivities. The value of our approach in practical applications was investigated by studying the effects of pinosylvin and 4,4′-dihydroxystilbene (DHS) on zebrafish as a vertebrate model.
- Yang., Jinfei,Wang, Chengniu,Sun, Yufeng,Man, Xuyan,Li, Jinxia,Sun, Fei
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supporting information
p. 1903 - 1906
(2019/05/02)
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- Pd/Cu-catalyzed facile approach to stilbenes: A novel diversity of TosMIC as an aryl source
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Pd/Cu-catalyzed Heck type cross-coupling reaction of p-toluenesulfonylmethyl isocyanide (TosMIC) with various styrenes to access stilbenes in DMSO solvent under mild conditions is developed. This efficient and simple approach employs TosMIC as an aryl sou
- Kadari, Lingaswamy,Palakodety, Radha Krishna
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supporting information
p. 1978 - 1981
(2019/07/03)
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- Xanthate-mediated synthesis of (E)-alkenes by semi-hydrogenation of alkynes using water as the hydrogen donor
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Semi-hydrogenation of alkynes is one of the most widely used methods for obtaining alkenes in laboratory preparation and in industry. Transition metal catalysts have been extensively studied for this transformation, but the tolerance of functional groups, such as pyridine,-OH,-NH2,-Bpin, and halides, and the toxicity of the trace amount of transition metal catalysts are still highly challenging. In this study, we report a general and robust strategy to achieve the semi-hydrogenation of alkynes using inexpensive and commercially available xanthate as the mediator. Mechanism studies support a non-radical process and H2O acts as the hydrogen donor.
- Luo, Xianglin,Chen, Xiuwen,Chen, Lu,Zhang, Kun,Li, Yibiao
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supporting information
p. 2170 - 2173
(2019/02/24)
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- Method of photo-induced catalytic selective synthesis of Z- and E-olefins
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The invention discloses a method of photo-induced catalytic selective synthesis of Z- and E-olefins. According to the method, a disubstituted acetylene compound is used as a starting raw material, a cheap acid is used as a hydrogen source, a phosphine is
- -
-
Paragraph 0040
(2019/10/01)
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- Method for selective synthesis of cis-olefins and trans-olefins by semi-reduction of alcohol hydrogen supply palladium-catalyzed alkynes
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The invention provides a method for selective synthesis of cis-olefins and trans-olefins by semi-reduction of alcohol hydrogen supply palladium-catalyzed alkynes. The method comprises the following steps: performing alkyne reduction reaction with TEOA, NaOAc, a catalyst, alcohol and alkynes in an organic solvent and generating the cis-olefins after reaction; performing alkyne reduction reaction with a ligand, a catalyst, alcohol and alkynes in an organic solvent and generating the trans-olefins after reaction; a reactor for the reduction reaction is a sealed pressure-resistant reactor, the reduction reaction temperature is 120-150 DEG C, and the reduction reaction time is 20-48 hours; the dosage of the catalyst is 5-20 percent of the molar dosage of the alkynes, and the dosage of the alcohol is 10-100 times of the molar dosage of the alkynes; the dosage of R, R-DIPAMP is 0.5-5 times of the molar dosage of the alkynes. According to the method provided by the invention, a catalyst systemhas extremely-high chemical reaction and stereo-selectivity and can synthesize cis-olefin products or trans-olefin products with high yield; the catalyst system is good universality to a substrate, and the alkynes containing various functional groups can be efficiently subjected to the highly-selective reduction reactions.
- -
-
Paragraph 0152-0154
(2019/06/07)
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- A tailored polymeric cationic tag-anionic Pd(ii) complex as a catalyst for the low-leaching Heck-Mizoroki coupling in flow and in biomass-derived GVL
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The [PdCl4]2- palladium complex has been immobilized on a polystyrene-type resin loaded with pincer-type imidazolium ionic tag binding sites. The catalytic system (Pd(ii)-POLI-TAG) has proved to be highly active in the definition of an efficient protocol for the Heck-Mizoroki coupling reaction under batch and flow conditions. Importantly, it is shown to be highly robust in combination with a safe non-toxic reaction medium, i.e. biomass-derived GVL, since it could be reused for multiple runs without significantly losing its activity.
- Mahmoudi, Hamed,Valentini, Federica,Ferlin, Francesco,Bivona, Lucia Anna,Anastasiou, Ioannis,Fusaro, Luca,Aprile, Carmela,Marrocchi, Assunta,Vaccaro, Luigi
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supporting information
p. 355 - 360
(2019/01/28)
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- Facile synthesis of a recyclable Pd-rGO/CNT/CaFe2O4 nanocomposite with high multifunctional photocatalytic activity under visible light irradiation
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We report a facile method to synthesize a magnetically separable Pd-rGO/CNT/CaFe2O4 photocatalyst. The incorporation of CNTs into rGO can form a conductive network structure to bridge the gaps between rGO sheets. This conductive netw
- Bagherzadeh, Mojtaba,Kaveh, Reyhaneh,Mahmoudi, Hamed
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p. 16257 - 16266
(2019/07/16)
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- First Cp*Co(III)-catalyzed Mizoroki-Heck coupling reactions of alkenes and aryl bromide/iodide
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A Cp*Co(CO)I2 catalyzed Mizoroki-Heck coupling of alkenes and aryl halide is established at feasible reaction conditions. The Cp*Co(III) catalyst excellently work to couple the aryl iodide and alkene, and produce up to 94% yield of the coupling
- Srivastava, Avinash K.,Satrawala, Naveen,Ali, Munsaf,Sharma, Charu,Joshi, Raj K.
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supporting information
(2019/11/13)
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- Metal-free denitrative arylation of β-nitrostyrenes using benzoyl peroxide: An easy access to: Trans -stilbenes
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A simple, novel and stereoselective synthesis of trans-stilbenes has been described using denitrative arylation of β-nitrostyrenes in the presence of benzoyl peroxide under metal-free conditions. The reaction is assumed to involve homolytic cleavage of benzoyl peroxide followed by decarboxylation to generate a phenyl radical, which brings about ipso-substitution of the nitro group of nitrostyrenes to afford trans-stilbenes.
- Yadav, Arvind Kumar,Singh, Krishna Nand
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supporting information
p. 14914 - 14917
(2017/12/15)
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- Fe-Catalyzed Cross-Coupling Reaction of Vinylic Ethers with Aryl Grignard Reagents
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Iron-catalyzed cross-coupling reaction of vinylic ethers with aryl Grignard reagents is described. The reaction proceeded at room temperature with catalytic amounts of an iron salt without the aid of costly ligands and additives. In this catalytic system, vinylic C?O bonds were preferentially cleaved over aromatic C?O bonds of aryl ethers or aryl sulfonates.
- Iwasaki, Takanori,Akimoto, Ryo,Kuniyasu, Hitoshi,Kambe, Nobuaki
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supporting information
p. 2834 - 2837
(2016/10/24)
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- Synthesis of stilbene derivatives via visible-light-induced cross-coupling of aryl diazonium salts with nitroalkenes using-NO2 as a leaving group
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The straightforward visible-light-induced synthesis of stilbene compounds via the cross-coupling of nitroalkenes and diazonium tetrafluoroborates under transition-metal-free conditions is described. The protocol uses green LEDs as light sources and eosin Y as an organophotoredox catalyst. Broad substrate scope and exclusive selectivity for the (E)-configuration of stilbenes are observed. This protocol proceeds via a radical pathway, with nitroalkenes serving as the radical acceptor, and the nitro group is cleaved during the process.
- Zhang, Na,Quan, Zheng-Jun,Zhang, Zhang,Da, Yu-Xia,Wang, Xi-Cun
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supporting information
p. 14234 - 14237
(2016/12/14)
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- An efficient trifunctional benzhydrazone ligated Pd(II) complex for Heck reaction of aryl bromides
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Synthesis of air and thermally stable trifunctional O, N, and O-terdentate benzhydrazone Pd(II) complex is reported and characterized by elemental analysis, spectral methods, and single crystal X-ray crystallographic technique. The new and reusable homogeneous catalyst has been effectively applied to the Mizoroki-Heck reaction of activated and deactivated aryl bromides with various olefins under mild reaction conditions in good to excellent yields up to 99%.
- Muthumari, Subramanian,Mohan, Nanjan,Ramesh, Rengan
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supporting information
p. 4170 - 4174
(2015/06/22)
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- Pd(II) complexes with amide-based macrocycles: Syntheses, properties and applications in cross-coupling reactions
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This work shows Pd(ii) complexes in a set of 13-membered amide-based macrocyclic ligands varied by the placement of e--donating and e--withdrawing substituents on the ligand framework. Ligands constitute a N4 square-planar cavity and optimally house the Pd(ii) ion. The solution-state structure via NMR and absorption spectra substantiates the solid-state structure obtained by crystallography. The electrochemical studies display the impact of electronic substituents on ligands that significantly influence the redox properties and also shift the locus of oxidation. These complexes were used in the Suzuki and Heck cross-coupling reactions. The moderate cross-coupling reaction results are due to limited redox accessibility that can be improved either by using substrates with a better leaving group or by placing electron-withdrawing substituents on the macrocyclic ligands.
- Kumar, Sushil,Jha, Rajeev Ranjan,Yadav, Sunil,Gupta, Rajeev
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p. 2042 - 2051
(2015/03/18)
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- Nickel(II) thiosemicarbazone complex catalyzed Mizoroki-Heck reaction
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Convenient synthesis of a new square planar nickel(II) naphthaldehyde thiosemicarbazone complex has been described. The composition of the complex has been established by elemental analysis, spectral methods, and single crystal X-ray crystallography. The
- Suganthy, Pandimuni Kalpaga,Prabhu, Rupesh Narayana,Sridevi, Venugopal Shamugham
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supporting information
p. 5695 - 5698
(2013/09/24)
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- Aerobic palladium-catalyzed arylation of alkenes using sodium sulfinates
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Palladium-catalyzed oxidative arylations of terminal alkenes could be performed using sodium sulfinates at 60 °C in air. The procedure gave various aryl alkenes after the desulfonylation of sodium arylsulfinates in the presence of a palladium catalyst. For instance, the reaction of styrene with sodium phenylsulfinate afforded trans-1,2-diphenylethylene in 80% yield without the formation of other stereoisomers. Georg Thieme Verlag Stuttgart · New York.
- Taniguchi, Nobukazu
-
supporting information
p. 2571 - 2574
(2013/12/04)
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- Selective arylation and vinylation at the α position of vinylarenes
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In intermolecular Heck reactions of styrene and vinylarenes, the aryl and vinyl groups routinely insert at the β position. However, selective insertion at the α position has been very rare. Herein, we provide a missing piece in the palette of Heck reaction, which gave >20:1 α selectivity. The key to our success is a new ferrocene 1,1′-bisphosphane (dnpf) that carries 1-naphthyl groups. Our mechanistic studies revealed that the high α selectivity is partly attributable to the steric effect of dnpf. The rigid and bulky 1-naphthyl groups of dnpf sterically disfavor β insertion. What the Heck! In intermolecular Heck reactions, insertion at the β position of aromatic olefins is very common, but reversal of the selectivity for selective α insertion has been a longstanding problem. A general method to couple aryl and vinyl triflates with aromatic olefins in >20:1 α selectivity is presented. The key to this successful approach is a new ferrocene bisphosphane with naphthyl groups on the phosphorus atom (see scheme; OTf=triflate). Copyright
- Zou, Yinjun,Qin, Liena,Ren, Xinfeng,Lu, Yunpeng,Li, Yongxin,Zhou, Jianrong
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supporting information
p. 3504 - 3511
(2013/07/05)
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- Cross-coupling of aryllithiums with aryl and vinyl halides in flow microreactors
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The use of Pd catalysts that contained a carbene ligand, such as PEPPSI-SIPr, speeded up the Murahashi coupling of ArLi with ArBr, by enabling its integration with the Br/Li exchange of ArBr with BuLi in flow. Space integration realized the rapid cross-coupling of two different ArBr substrates. However, the cross-coupling reaction with vinyl halides could not be achieved under similar conditions. Pd(OAc)2 was an effective catalyst, and the space integration of the Br/Li exchange of ArBr with BuLi and the Murahashi coupling with vinyl halides was successfully achieved.
- Nagaki, Aiichiro,Moriwaki, Yuya,Haraki, Suguru,Kenmoku, Akira,Takabayashi, Naofumi,Hayashi, Atsushi,Yoshida, Jun-Ichi
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supporting information; experimental part
p. 1061 - 1068
(2012/07/31)
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- Oxidative Mizoroki-Heck-type reaction of arylsulfonyl hydrazides for a highly regio- and stereoselective synthesis of polysubstituted alkenes
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A useful source: Arylsulfonyl hydrazides have been identified as synthetically useful aryl sources for the Pd(OAc)2 catalyzed oxidative Mizoroki-Heck-type reaction under molecular oxygen to provide a convenient access to polysubstituted alkenes in a highly regio- and stereoselective manner (see scheme). The reaction well tolerates various functional groups such as alkoxy, halo, alcohol, carboxylic acid, ester, amide, sulfonamide, and sulfone. Copyright
- Yang, Fu-Lai,Ma, Xian-Tao,Tian, Shi-Kai
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supporting information; experimental part
p. 1582 - 1585
(2012/03/11)
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- Catalytic application of dinuclear palladium(II) bis(thiosemicarbazone) complex in the Mizoroki-Heck reaction
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A convenient synthesis of new square planar dinuclear palladium(II) terephthaldehyde bis(thiosemicarbazone) complex has been described. The compositions of the complex have been established by elemental analysis, spectral methods and single crystal X-ray crystallographic technique. The new complex acts as an active recyclable homogeneous catalyst for the Mizoroki-Heck reaction of electron deficient (activating) and electron rich (deactivating) aryl halides with various olefins under optimized conditions.
- Prabhu, Rupesh Narayana,Ramesh, Rengan
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supporting information
p. 5961 - 5965,5
(2020/08/20)
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- Copper-catalyzed alkene arylation with diaryliodonium salts
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Alkenes and arenes represent two classes of feedstock compounds whose union has fundamental importance to synthetic organic chemistry. We report a new approach to alkene arylation using diaryliodonium salts and Cu catalysis. Using a range of simple alkenes, we have shown that the product outcomes differ significantly from those commonly obtained by the Heck reaction. We have used these insights to develop a number of new tandem and cascade reactions that transform readily available alkenes into complex arylated products that may have broad applications in chemical synthesis.
- Phipps, Robert J.,McMurray, Lindsay,Ritter, Stefanie,Duong, Hung A.,Gaunt, Matthew J.
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supporting information; experimental part
p. 10773 - 10776
(2012/08/07)
-
- Effects of substituent and solvent on the UV absorption energy of 4,4′-disubstituted stilbenes
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Twenty five samples of 4,4′-disubstituted stilbene derivatives were synthesized, and their UV absorption max wavelengths were determined in over 10 kinds of solvents including cyclohexane, ether, chloroform, acetonitrile and ethanol, in which 242 experimental data were recorded. The effects of substituents and solvents on the energy of their UV absorption max wavelengths were discussed. The research results showed: the energy of UV absorption max wavelengths of 4,4′-disubstituted stilbenes was mainly affected by their intramolecular structure (substituent effect) in a given solvent, that is, the energy is dominated by both of excited-state substituent parameter σ CC ex and polar substituent constant σ p. While their energy was dominated by the substituent effect and solvent effect in different kinds of solvents. An equation quantifying the energy of UV absorption max wavelengths of 4,4′-disubstituted stilbenes was developed. In addition, it is found that the n-octanol/water partition coefficient (logP) is more effective than the solvatochromic dye (E T(30)) in scaling the solvent effect. The equation employed the parameter logP has a better correlation and more specific physical meaning. Further, the energies of UV absorption max wavelengths of some reported compounds were predicted by the obtained equation, which are in agreement with their experimental values.
- Cao, Chenzhong,Chen, Guanfan,Wu, Yaxin
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scheme or table
p. 1735 - 1744
(2012/05/05)
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- H2SO4-promoted synthesis of (E)-stilbenes from substituted phenylacetones and substituted benzaldehydes through tandem aldol-Grob reaction
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Stilbene derivates (stilbenoids) are present in plants and show a wide range of biological activities and potential therapeutic value. In continuation of our natural product synthesis program, an efficient, simple, and practical method has been developed to regioselectively synthesize (E)-stilbenes using H2SO4 as a catalyst in a short time (30-60 s) at room temperature in good to excellent yields.
- Narender,Papi Reddy,Tiwari, Sriniwas
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experimental part
p. 1572 - 1583
(2011/06/27)
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- Palladium-catalyzed desulfitative heck-type reaction of aryl sulfinic acids with alkenes
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An efficient protocol has been developed for the desulfitative Heck-type reaction of aryl sulfinic acids with a variety of alkenes in the presence of a catalytic amount of Pd(OAc)2 and inexpensive Cu(OAc)2 as oxidant. This method does not require a ligand or a base, thereby broadening the scope of Pd-catalyzed coupling reactions. Copyright
- Wang, Guan-Wu,Miao, Tao
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p. 5787 - 5790
(2011/06/23)
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- Mizoroki-heck-type reaction mediated by potassium tert-butoxide
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In the absence of transition-metal catalysts, a Mizoroki-Heck-type reaction proceeded to give stilbene derivatives in a simple manner using an aryl halide, a styrene derivative, KOtBu, EtOH, and DMF (see scheme; DMF=N,N- dimethylformamide).
- Shirakawa, Eiji,Zhang, Xuejing,Hayashi, Tamio
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supporting information; experimental part
p. 4671 - 4674
(2011/06/27)
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- Wittig reaction with ion-supported Ph3P
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Ion-supported Ph3P, 4-(diphenylphosphino)benzyltrimethylammonium bromide A and N-methyl-N-[4-(diphenylphosphino)benzyl]pyrrolidinium bromide B, were used for the Wittig reaction. Ion-supported phosphonium salts A1 and B1, which were prepared from the reactions of ion-supported Ph3P A and B with ethyl bromoacetate, respectively, reacted with aromatic and aliphatic aldehydes in the presence of K2CO3 to give the corresponding α,β-unsaturated ethyl esters in good yields with high purity by simple filtration of the reaction mixture and subsequent removal of the solvent from the filtrate. Similarly, ion-supported phosphonium salts A2 and B2, which were prepared from the reactions of ion-supported Ph3P A and B with p-methylbenzyl bromide, respectively, reacted with aromatic and aliphatic aldehydes in the presence of NaH to provide the corresponding p-methylstyrene derivatives in good yields with high purity by simple filtration of the reaction mixture and the subsequent removal of the solvent from the filtrate. In both reactions, the co-product, ion-supported Ph3PO, could be obtained quantitatively by simple filtration, and was converted into the corresponding ion-supported Ph3P A and B again in high yields using dimethyl sulfate, followed by the reduction with LiAlH4. Recovered and regenerated ion-supported Ph3P A and B could be reused for the same Wittig reaction while maintaining good yields of ethyl (E)-3-(4′-chlorophenyl)-2-propenoate and 1-(4′-chlorophenyl)-2- (4″-methylphenyl)ethene with high purity by simple filtration and removal of the solvent from the filtrate.
- Shimojuh, Naoya,Imura, Yumi,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 951 - 957
(2011/03/18)
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- Lewis acid promoted carbon - Carbon double-bond formation via organozinc reagents and carbonyl compounds
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(Chemical Equation Presented) Using cheap and readily available AlCl3 as Lewis acid, functionalized aldehydes react with organozinc reagents to give (E)-alkenes stereoselectively in high yields. 2009 American Chemical Society.
- Peng, Zhi-Yong,Ma, Fang-Fang,Zhu, Lv-Feng,Xie, Xiao-Min,Zhang, Zhaoguo
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supporting information; experimental part
p. 6855 - 6858
(2009/12/31)
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- Three phase microemulsion/sol-gel system for aqueous C-C coupling of hydrophobic substrates
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Heck, Stille, Suzuki and three-component coupling reactions with hydrophobic substrates have been carried out in water. The substrates are initially transformed by a general procedure into a microemulsion, which consists of nearly 90% water with the aid of sodium dodecyl sulfate and either PrOH or BuOH. The surfactant carries the molecules of the substrates to Pd(OAc)2 entrapped within a hydrophobicitized silica sol-gel matrix where the coupling between the substrates is assumed to take place. The products are then returned by the surfactant into the microemulsion from which it can be released. The immobilized palladium catalyst is leach proof and recyclable. It can be used in various coupling processes at least six times without loss of activity. Experiments with D2O have revealed that the water does not take part in the coupling process, but it has an effect on the pore size of the sol-gel matrix, which hosts the palladium catalyst. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Tsvelikhovsky, Dmitry,Blum, Jochanan
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scheme or table
p. 2417 - 2422
(2009/04/06)
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- Room-temperature Kumada cross-coupling of unactivated aryl chlorides catalyzed by N-heterocylic carbene-based nickel(II) complexes
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(Chemical Equation Presented) The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, and heteroaryl chlorides catalyzed by nickel(II) complexes containing pyridine-functionalized NHC ligands is described. The catalysts are so active that the reactions proceed at room temperature in excellent yields.
- Xi, Zhenxing,Liu, Bin,Chen, Wanzhi
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p. 3954 - 3957
(2008/09/19)
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- Microwave enhanced cross-coupling reactions involving alkenyl- and alkynyltrifluoroborates
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Cross-coupling reactions of potassium arylvinyltrifluoroborates with aryl iodides in the presence of a palladium catalyst occur rapidly utilizing microwave irradiation. The coupled products are produced in excellent yields. Alkynyltrifluoroborates also undergo the coupling reaction.
- Kabalka, George W.,Al-Masum, Mohammad,Mereddy, Arjun R.,Dadush, Eric
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p. 1133 - 1136
(2007/10/03)
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- Synthesis of (E)-alkenes via hydroindation of C{triple bond, long}C in InCl3-NaBH4 system
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In InCl3-NaBH4-MeCN system, terminal aryl alkynes could couple with aryl iodides and bromides to give disubstituted alkenes via hydroindation of C{triple bond, long}C. In the similar way, (E)-alkenylsilanes were synthesized via reduction of alkynylsilanes in tetrahydrofuran (THF) in high yields. The processes showed high regio- and stereoselectivity.
- Wang, Chunyan,Yan, Lei,Zheng, Zhiguo,Yang, Deyu,Pan, Yuanjiang
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p. 7712 - 7717
(2007/10/03)
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- Triaryl phosphine-functionalized N-heterocyclic carbene ligands for Heck reaction
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A new type of triaryl phosphine-functionalized imidazolium salts 6 were prepared. Their palladium complexes, generated in situ, were successfully applied in the palladium-catalyzed Heck reaction. Using 1 mol% of Pd(dba) 2 and 1 mol% 6c in the presence of 2 equiv of K2CO 3 in DMAc has proven to be highly efficient for the coupling of a wide array of aryl bromides and iodides with acrylates in excellent yield. The coupling of 4-bromotoluene with various styrene derivatives catalyzed by Pd/6c complex also gave good results. Graphical Abstract.
- Wang, Ai-E,Xie, Jian-Hua,Wang, Li-Xin,Zhou, Qi-Lin
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p. 259 - 266
(2007/10/03)
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- Catalytic activity of Pd(II) and Pd(II)/DAB-R systems for the Heck arylation of olefins
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Palladium-catalyzed reactions of aryl bromides with various olefins involving Pd(II)/diazabutadiene (DAB-R) systems have been investigated. The scope of a coupling process using Pd(II) sources and an α-diimine as ligand in the presence of Cs2CO3 as base was tested using various substrates. The Pd(OAc)2/ DAB-Cy (1, DAB-Cy=1,4-dicyclohexyl-diazabutadiene) system presents the highest activity with respect to electron-neutral and electron-deficient aryl bromides in coupling with electron rich olefins. The synthesis and X-ray characterization of a Pd(II)-diazabutadiene ligand is reported. Extensive optimization experiments showed that another Pd(II) source, Pd(acac)2 (acac=acetylacetonate), proved to activate aryl bromides at high temperatures, low catalyst loadings when the appropriate concentration of nBu4NBr additive was employed. The effect of the DAB-Cy ligand is important at very low catalyst loadings and high temperatures. Pd(acac)2 and Pd(acac)2 /DAB-Cy precatalysts were very effective for the arylation of various olefins with aryl bromides with respect to reaction rate, catalyst loadings, and functional group tolerance.
- Grasa, Gabriela A.,Singh, Rohit,Stevens, Edwin D.,Nolan, Steven P.
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p. 269 - 279
(2007/10/03)
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- Platinum-catalyzed cross-couplings of organoboronic acids with aryl iodides
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Tetrakis(triphenylphosphine)platinum in DMF was utilized as a mild catalyst for cross coupling reactions of organoboronic acids with aryl iodides. The present reactions exhibited excellent group-selectivity where couplings of organoboronic acids 2a-e with 4-bromo-1-iodobenzene (4) give 4-arylbromobenzenes 5a-b and 4-alkenylbromobenzenes 5c-e in excellent yields.
- Oh, Chang Ho,Lim, Young Mook,You, Choong Ho
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p. 4645 - 4648
(2007/10/03)
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- Electron Demand in the Transition State of the Cyclopropylidene to Allene Ring Opening
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The electronic structure of the transition state for the cyclopropylidene to allene conversion has been probed.The methodology involved the relative rates of ring opening vs trapping by MeOH for a series of variously substituted 2,3-diarylcyclopropylidenes.With the assumption that the rate of trapping was unaffected by substituents, a Hammett correlation was constructed.The negative value (-0.72) for ρ indicated that the carbenic center attracts electron density in the ring-opening transition state, much like the cyclopropyl cation to allyl cation transition state.Temperature-dependent studies showed that the observed preference for ring opening was driven by entropy factors.Also, using reasonable estimates for the close to diffusion-controlled trapping activation enthalpies, the derived enthalpies for ring opening were in close agreement with the best theoretical values.
- Warner, Philip,Sutherland, Robert
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p. 6294 - 6300
(2007/10/02)
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- Carbon-Hydrogen vs. Carbon-Carbon Bond Cleavage of 1,2-Diarylethane Radical Cations in Acetonitrile-Water
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Radical cations of 1,2-diarylethanes and 1-phenyl-2-arylethanes (Ar = phenyl, p-tolyl, p-anisyl) were generated in acidic 70percent acetonitrile-water by Cu2+-catalyzed peroxydisulfate oxidation.The radical cations fragment mainly by loss of benzylic protons (C-H cleavage) rather than by alkyl C-C bond cleavage.The radical cation of 2,3-dimethyl-2,3-diphenylbutane fragments efficiently by C-C cleavage, forming cumyl radical and cumyl cation.Oxidations of bibenzyl-bicumyl mixtures show selective oxidation of bicumyl dependent on total substrate concentration, providing evidence of equilibrating radical cations and showing that bicumyl fragments faster than bibenzyl loses protons.The effects of reaction conditions and substrate structure on reactivity are discussed.
- Camaioni, Donald M.,Franz, James A.
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p. 1607 - 1613
(2007/10/02)
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- Locally Excited Triplet State Production from Excited Charge-Transfer Complexes
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The photochemistry and photophysics of a series of homologous charge-transfer complexes, involving substituted stilbenes and fumaronitrile, have been examined.The rate constants for fluorescence (kf), production of the stilbene triplet state (kT), and decay back to the ground state (kd) have been determined.The values of kT for the complexes were found to be logarithmically related to the energy gap between the initial and final states.In contrast, kf and kd are independent of the identity of the substituted stilbene.These results verify the previously proposed mechanism of stilbene isomerization in the parent system.
- Adams, Bobby K.,Cherry, William R.
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p. 6904 - 6907
(2007/10/02)
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