- Nickel-Catalyzed Regiodivergent Reductive Hydroarylation of Styrenes
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We report a ligand-controlled nickel-catalyzed reductive hydroarylation of styrenes with predictable and controllable regioselectivity. With a diamine ligand, the reaction produces selective linear hydroarylation products. Alternatively, with a chiral PyrOx ligand, branch-selective enantioenriched 1,1-diarylalkane products are obtained. Preliminary mechanistic results are consistent with a reductive Heck process.
- Xue, Yuhang,Chen, Jian,Song, Peihong,He, Yuli,Zhu, Shaolin
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p. 1647 - 1651
(2021/07/02)
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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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supporting information
p. 7552 - 7562
(2021/06/28)
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- Chemoselective Hydrogenation of Alkynes to (Z) -Alkenes Using an Air-Stable Base Metal Catalyst
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A highly selective hydrogenation of alkynes using an air-stable and readily available manganese catalyst has been achieved. The reaction proceeds under mild reaction conditions and tolerates various functional groups, resulting in (Z)-alkenes and allylic alcohols in high yields. Mechanistic experiments suggest that the reaction proceeds via a bifunctional activation involving metal-ligand cooperativity.
- Zubar, Viktoriia,Sklyaruk, Jan,Brzozowska, Aleksandra,Rueping, Magnus
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supporting information
p. 5423 - 5428
(2020/07/24)
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- Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
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Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
- Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
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p. 4968 - 4980
(2020/08/19)
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- Intermolecular oxyarylation of olefins with aryl halides and TEMPOH catalyzed by the phenolate anion under visible light
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The phenolate anion was discovered as a new photocatalyst with strong reduction potentials. Under visible light irradiation, the phenolate anion enabled the reduction of (hetero)aryl halides (including electron-rich aryl chlorides) to (hetero)aryl radicals through single electron transfer. Based on this new photocatalyst, a novel and efficient photocatalytic protocol for the intermolecular oxyarylation of olefins with aryl halides and TEMPOH was developed. The developed three-component coupling reaction proceeded under redox-neutral reaction conditions with stable and readily available synthons and exhibited broad substrate scope. The utility of this process was further highlighted by the diversified chemical manipulation of the resulting oxyarylation products and the late-stage modification of active pharmaceutical ingredients.
- Li, Xipan,Liang, Kangjiang,Liu, Qian,Shen, Lei,Wei, Delian,Xia, Chengfeng,Zheng, Liyan
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p. 6996 - 7002
(2020/07/23)
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- The synergy between the CsPbBr3nanoparticle surface and the organic ligand becomes manifest in a demanding carbon-carbon coupling reaction
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We demonstrate here the suitability of CsPbBr3nanoparticles as photosensitizers for a demanding photoredox catalytic homo- and cross-coupling of alkyl bromides at room temperature by merely using visible light and an electron donor, thanks to the cooperative action between the nanoparticle surface and organic capping.
- Casadevall, Carla,Claros, Miguel,Galian, Raquel E.,Lloret-Fillol, Julio,Pérez-Prieto, Julia,Rosa-Pardo, Ignacio,Schmidt, Luciana
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supporting information
p. 5026 - 5029
(2020/05/18)
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- Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides
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A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which pro
- Fang, Ping,Jiao, Ke-Jin,Liu, Dong,Ma, Hong-Xing,Mei, Tian-Sheng,Qiu, Hui
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supporting information
p. 6520 - 6524
(2020/01/24)
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- "bulky-Yet-Flexible" α-Diimine Palladium-Catalyzed Reductive Heck Cross-Coupling: Highly Anti-Markovnikov-Selective Hydroarylation of Alkene in Air
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To pursue a highly regioselective and efficient reductive Heck reaction, a series of moisture-and air-stable α-diimine palladium precatalysts were rationally designed, readily synthesized, and fully characterized. The relationship between the structures of the palladium complexes and the catalytic properties was investigated. It was revealed that the"bulky-yet-flexible"palladium complexes allowed highly anti-Markovnikov-selective hydroarylation of alkenes with (hetero)aryl bromides under aerobic conditions. Further synthetic application of the present protocol could provide rapid and straightforward access to functional and biologically active molecules.
- Yang, Xu-Wen,Li, Dong-Hui,Song, A-Xiang,Liu, Feng-Shou
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p. 11750 - 11765
(2020/10/23)
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- HIGHLY SELECTIVE ELECTROCHEMICAL HYDROGENATION OF ALKYNES
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Disclosed are electrochemical methods to prepare an alkane or an alkene, such as a cis- alkene, from an alkyne, or an alkane from an alkene. The method utilizes an electrochemical cell having a cathode and an anode and a reactor.
- -
-
Page/Page column 7
(2020/10/20)
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- Celite-Polyaniline supported palladium catalyst for chemoselective hydrogenation reactions
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Polyaniline coated on particles of celite is used as support to load palladium catalyst. This heterogenized Celite?PANI?Pd system, is used as an efficient catalyst for chemoselective hydrogenation reactions. The catalyst is characterized by usual spectral, analytical techniques and studied for hydrogenation reactions at ambient conditions. The mild reaction conditions allow the control over the reactions and excellent selectivity is achieved in number of conversions. Hydrogenation of a carbon–carbon double bond was favored over other polar π-bond systems, while labile functional groups such as benzyl ether, benzyl esters, cyano, nitro and halogen remained unaffected. Primary amines were converted to N,N-dimethyl amines with formaldehyde, the double bond of coumarin was selectively hydrogenated without opening of the lactone functionality.
- Patel, Heta A.,Rawat, Maitreyee,Patel, Arun L.,Bedekar, Ashutosh V.
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- Nickel-catalyzed anti-Markovnikov hydroarylation of alkenes
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We have developed a nickel-catalyzed hydroarylation of alkenes using aryl halides as coupling partners. Excellent anti-Markovnikov selectivity is achieved with aryl-substituted alkenes and enol ethers. We also show that hydroarylation occurs with alkyl substituted alkenes to yield linear products. Preliminary examination of the reaction mechanism suggests irreversible hydrometallation as the selectivity determining step of the hydroarylation.
- Nguyen, Julia,Chong, Andrea,Lalic, Gojko
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p. 3231 - 3236
(2019/03/21)
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- Bioinspired Palladium Nanoparticles Supported on Soil-Derived Humic Acid Coated Iron-Oxide Nanoparticles as Catalyst for C–C Cross-Coupling and Reduction Reactions
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Abstract: Pd nanoparticles supported on humic acid-coated nanoferrites as magnetically-recoverable catalyst was expediently prepared from inexpensive precursors and characterized by techniques such as SEM, TEM, XPS, FT-IR, XRD, ICP-AES, EDX. The as made catalyst displayed an admirable catalytic activity towards the Suzuki–Miyaura cross-coupling reaction of aryl halides (or) aryl diazonium salts with aryl boronic acid in non-toxic solvent EtOH/water under mild conditions. The same catalyst showed high efficiency for the Heck reaction of aryl halides with styrene was carried out with high efficiency offering good yields under ligand-free conditions. Additionally, the reduction of olefins using molecular hydrogen was also achieved using the same catalyst under ambient and base-free conditions affording the products in good to excellent yields. The magnetic activity of nano-Fe3O4 allowed the effortless recovery of the catalyst and demonstrated subsequent recyclability up to 5 cycles without a significant loss in the activity. Graphical Abstract: [Figure not available: see fulltext.].
- Chinchole, Anurag N.,Dubey, Abhishek V.,Kumar, A. Vijay
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p. 1224 - 1236
(2019/02/26)
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- Deaminative Reductive Cross-Electrophile Couplings of Alkylpyridinium Salts and Aryl Bromides
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A nickel-catalyzed reductive cross-coupling of alkylpyridinium salts and aryl bromides has been developed using Mn as the reductant. Both primary and secondary alkylpyridinium salts can be used, and high functional group and heterocycle tolerance is observed, including for protic groups. Mechanistic studies indicate the formation of an alkyl radical, and controlling its fate was key to the success of this reaction.
- Liao, Jennie,Basch, Corey H.,Hoerrner, Megan E.,Talley, Michael R.,Boscoe, Brian P.,Tucker, Joseph W.,Garnsey, Michelle R.,Watson, Mary P.
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supporting information
p. 2941 - 2946
(2019/04/30)
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- One-Pot Electrochemical Nickel-Catalyzed Decarboxylative Sp2-Sp3 Cross-Coupling
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A one-pot electrochemical nickel-catalyzed decarboxylative sp2-sp3 cross-coupling reaction has been developed using redox-active esters prepared in situ from alkyl carboxylates and N-hydroxyphthalimide tetramethyluronium hexafluorophosphate (PITU). This undivided cell one-pot method enables C-C bond formation using inexpensive, benchtop-stable reagents with isolated yields up to 95% with good functional group tolerance, which includes nitrile, ketone, ester, alkene and selectivity over other aromatic halogens.
- Koyanagi, Takaoki,Herath, Ananda,Chong, Ashley,Ratnikov, Maxim,Valiere, Andrew,Chang, Jim,Molteni, Valentina,Loren, Jon
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supporting information
p. 816 - 820
(2019/01/30)
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- Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
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Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
- Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
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supporting information
p. 16490 - 16494
(2019/11/03)
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- An N-heterocyclic carbene ligand promotes highly selective alkyne semihydrogenation with copper nanoparticles supported on passivated silica
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We report a surface organometallic route that generates copper nanoparticles (NPs) on a silica support while simultaneously passivating the silica surface with trimethylsiloxy groups. The material is active for the catalytic semihydrogenation of phenylalkyl-, dialkyl- and diaryl-alkynes and displays high chemo- and stereoselectivity at full alkyne conversion to corresponding (Z)-olefins in the presence of an N-heterocyclic carbene (NHC) ligand. Solid-state NMR spectroscopy using the NHC ligand 13C-labeled at the carbenic carbon reveals a genuine coordination of the carbene to Cu NPs. The presence of distinct Cu surface environments and the coordination of the NHC to specific Cu sites likely account for the increased selectivity.
- Kaeffer, Nicolas,Liu, Hsueh-Ju,Lo, Hung-Kun,Fedorov, Alexey,Copéret, Christophe
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p. 5366 - 5371
(2018/06/27)
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- Modular radical cross-coupling with sulfones enables access to sp3-rich (fluoro)alkylated scaffolds
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Cross-coupling chemistry is widely applied to carbon-carbon bond formation in the synthesis of medicines, agrochemicals, and other functional materials. Recently, single-electron-induced variants of this reaction class have proven particularly useful in the formation of C(sp2)-C(sp3) linkages, although certain compound classes have remained a challenge. Here, we report the use of sulfones to activate the alkyl coupling partner in nickel-catalyzed radical cross-coupling with aryl zinc reagents. This method's tolerance of fluoroalkyl substituents proved particularly advantageous for the streamlined preparation of pharmaceutically oriented fluorinated scaffolds that previously required multiple steps, toxic reagents, and nonmodular retrosynthetic blueprints. Five specific sulfone reagents facilitate the rapid assembly of a vast set of compounds, many of which contain challenging fluorination patterns.
- Merchant, Rohan R.,Edwards, Jacob T.,Qin, Tian,Kruszyk, Monika M.,Bi, Cheng,Che, Guanda,Bao, Deng-Hui,Qiao, Wenhua,Sun, Lijie,Collins, Michael R.,Fadeyi, Olugbeminiyi O.,Gallego, Gary M.,Mousseau, James J.,Nuhant, Philippe,Baran, Phil S.
-
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- Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with Organoboron Compounds
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A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni?H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C?H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.
- Xiao, Li-Jun,Cheng, Lei,Feng, Wei-Min,Li, Mao-Lin,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 461 - 464
(2018/02/21)
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- Cobalt-catalyzed (Z)-selective semihydrogenation of alkynes with molecular hydrogen
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Cobalt-catalyzed highly (Z)-selective semihydrogenation of alkynes using molecular H2 was developed using commercially available and cheap cobalt precursors. A variety of (Z)-alkenes were obtained in moderate to excellent selectivities [(Z)-alkene/(E)-alkene/alkane ratio up to >99 : 1 : 1] and it was found that the readily available ethylenediamine ligand is crucial in determining the selectivity.
- Chen, Caiyou,Huang, Yi,Zhang, Zongpeng,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 4612 - 4615
(2017/04/28)
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- Thermal Rearrangement of Sulfamoyl Azides: Reactivity and Mechanistic Study
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The rearrangement of sulfamoyl azides under thermal conditions to form a C-C bond while breaking two C-N bonds is reported. Mechanistic study shows that this reaction goes through a Curtius-type rearrangement to form a 1,1-diazene, then which rearranges possibly through both a concerted rearrangement process and a stepwise radical process. This rearrangement could be used in the synthesis of complex biologically active molecules, such as sterols, and piperine derivatives.
- Zou, Xiaodong,Zou, Jiaqi,Yang, Lizheng,Li, Guigen,Lu, Hongjian
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p. 4677 - 4688
(2017/05/12)
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- Iron complexes of a bidentate picolyl-NHC ligand: Synthesis, structure and reactivity
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The synthesis, structure and reactivity of bidentate picolyl N-heterocyclic carbene (NHC) iron compounds were studied. Compounds [FeBr(HL)2]Br (1), [FeBr(HL)(HMDS)] (2) and [FeBr2(HL)] (3) (HL = 1-mesityl-3-(pyridin-2-ylmethyl)imidazol-1-ylidene, HMDS = hexamethyldisilazide) were prepared from H2LBr with suitable amounts of Fe(HMDS)2 or in situ prepared [Fe(HMDS)Br]. The deprotonation of 1 with 2 eq. of LiHMDS gave [FeL2] (4), featuring dearomatized pyridine moieties with exocyclic C-C double bonds. The protonation of 4 with 2 eq. of PPh3·HBr results in the formation of 1. Attempted deprotonation of 3 using benzyl Grignard as the base resulted in transmetalation products [FeBnBr(HL)] (5) and [FeBn2(HL)] (6). Exposure of 6 to CO resulted in the formation of diamagnetic compound [Fe(CO)3(HL)] (7) and dibenzyl ketone. Prolonged exposure of 7 to CO with heating induces pyridine dissociation, affording [Fe(CO)4(HL-κC)] (8). Treatment of compound 6 with an equimolar amount of p-methoxybenzyl bromide yielded homo- and cross-coupling products.
- Liang, Qiuming,Janes, Trevor,Gjergji, Xhoana,Song, Datong
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supporting information
p. 13872 - 13880
(2016/09/09)
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- Reduction of diphenylacetylene using Al powder in the presence of noble metal catalysts in water
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Diphenylacetylenes can be reduced to the corresponding diphenylethanes (2) in water in excellent yield using Al powder and Pd/C at 60?°C for 3?h in a sealed tube. In addition, the complete reduction of both aromatic rings required 80?°C for 15?h with Al powder in the presence of Pt/C. However, the nature of hydrogenated product formed was found to be strongly influenced by the reaction temperature, time, volume of water and the amount of catalyst being employed.
- Rayhan, Ummey,Kowser, Zannatul,Redshaw, Carl,Yamato, Takehiko
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supporting information
p. 6943 - 6947
(2016/10/14)
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- Reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis
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A method for the reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis was developed, thus resulting in the highly regioselective formation of various 1,1-diarylalkanes, including a biologically active molecule. Under the applied reaction conditions, high levels of functional-group tolerance were observed, and the reductive cross-coupling of internal alkynes with aryl bromides afforded trisubstituted alkenes. Forming a Co-op: A method for the reductive cross-coupling of conjugated arylalkenes or internal alkynes and aryl bromides with hydrosilanes using cooperative palladium/copper catalysis was developed. The resulting 1,1-diarylalkanes and trisubstituted alkenes were isolated with high regio- and stereoselectivity. Under the applied reaction conditions, high levels of functional-group tolerance were observed.
- Semba, Kazuhiko,Ariyama, Kenta,Zheng, Hong,Kameyama, Ryohei,Sakaki, Shigeyoshi,Nakao, Yoshiaki
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supporting information
p. 6275 - 6279
(2016/05/24)
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- Two dimensional inorganic electride-promoted electron transfer efficiency in transfer hydrogenation of alkynes and alkenes
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A simple and highly efficient transfer hydrogenation of alkynes and alkenes by using a two-dimensional electride, dicalcium nitride ([Ca2N]+·e-), as an electron transfer agent is disclosed. Excellent yields in the transformation are attributed to the remarkable electron transfer efficiency in the electride-mediated reactions. It is clarified that an effective discharge of electrons from the [Ca2N]+·e- electride in alcoholic solvents is achieved by the decomposition of the electride via alcoholysis and the generation of ammonia and Ca(OiPr)2. We found that the choice of solvent was crucial for enhancing the electron transfer efficiency, and a maximum efficiency of 80% was achieved by using a DMF mixed isopropanol co-solvent system. This is the highest value reported to date among single electron transfer agents in the reduction of C-C multiple bonds. The observed reactivity and efficiency establish that electrides with a high density of anionic electrons can readily participate in the reduction of organic functional groups.
- Kim, Ye Ji,Kim, Sun Min,Cho, Eun Jin,Hosono, Hideo,Yang, Jung Woon,Kim, Sung Wng
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p. 3577 - 3581
(2015/05/27)
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- Cross-coupling of nonactivated primary and secondary alkyl halides with aryl Grignard reagents catalyzed by chiral iron pincer complexes
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Iron(III) bisoxazolinylphenylamido (bopa) pincer complexes are efficient precatalysts for the cross-coupling of nonactivated primary and secondary alkyl halides with phenyl Grignard reagents. The reactions proceed at room temperature in moderate to excellent yields. A variety of functional groups can be tolerated. The enantioselectivity of the coupling of secondary alkyl halides is low.
- Bauer, Gerald,Cheung, Chi Wai,Hu, Xile
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p. 1726 - 1732
(2015/06/16)
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- Development of the direct Suzuki-Miyaura cross-coupling of primary B-alkyl MIDA-boronates and aryl bromides
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The development of a palladium-catalyzed sp3-sp2 Suzuki-Miyaura cross-coupling of B-alkyl-N-methyliminodiacetyl (B-alkyl MIDA) boronates and (hetero)aryl bromides is reported. This transformation is tolerant of a variety of functional groups (F, NO2, CN, Cl, COCH3, and CHO). B-Alkyl MIDA boronates allow an efficient cross-coupling reaction directed toward the synthesis of unsymmetrical methylene diaryls as well as alkylated arenes in good to excellent yields.
- St. Denis, Jeffrey D.,Scully, Conor C. G.,Lee, C. Frank,Yudin, Andrei K.
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supporting information
p. 1338 - 1341
(2014/04/03)
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- Plasma synthesis of oxidized graphene foam supporting Pd nanoparticles as a new catalyst for one-pot synthesis of dibenzyls
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We have developed an environmentally-friendly method for the synthesis of Pd nanoparticle (Pd NPs) decorated different graphene supports, and the morphology and structure of the hybrids are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and elemental mappings. Four hybrid materials based on graphene foam (GF), oxidized graphene foam (OGF), graphene oxide (GO) and reduced graphene oxide (RGO) have been used to catalyze Heck coupling reactions, and the effect of support on the activity of the hybrid material has been studied. Our results have revealed that Pd NP decorated OGF (Pd/OGF) is the most active catalyst, showing better performance than the commercial Pd/C catalyst. More importantly, the Pd/OGF catalyst has been successfully used for one-pot synthesis of dibenzyls with different aryl bromides and olefins, which has simplified the separation and purification process and realized a green organic synthesis process. This journal is
- Ren, Liang,Yang, Fan,Wang, Chunxia,Li, Yongfeng,Liu, Hailing,Tu, Zhiqiang,Zhang, Liqiang,Liu, Zhichang,Gao, Jinsen,Xu, Chunming
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p. 63048 - 63054
(2015/02/19)
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- A clean and selective radical homocoupling employing carboxylic acids with titania photoredox catalysis
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A titania photoredox catalysis protocol was developed for the homocoupling of C-centered radicals derived from carboxylic acids. Intermolecular reactions were generally efficient and selective, furnishing the desired dimers in good yields under mild neutral conditions. Selective cross-coupling with two acids proved unsuccessful. An intra-molecular adaptation enabled macrocycles to be prepared, albeit in modest yields. (Chemical Equation Presented).
- Manley, David W.,Walton, John C.
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supporting information
p. 5394 - 5397
(2015/02/19)
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- Cross-coupling of alkyl halides with aryl or alkyl Grignards catalyzed by dinuclear Ni(ii) complexes containing functionalized tripodal amine-pyrazolyl ligands
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Structurally distinctive dinuclear Ni(ii) complexes with furan or thiophene tethered amine-pyrazolyl tripodal hybrid ligands have been synthesized and crystallographically characterized. All complexes are catalytically active towards cross-coupling of aryl/alkyl Grignard reagents with β-H containing alkyl halides at room temperature in the presence of N,N,N',N'- tetramethylethylenediamine (TMEDA). The catalytic efficacy of the complexes is dependent on the tether substituent at the central amine. Two species, Ni(ii) TMEDA and Mg(ii) TMEDA complexes, have been isolated from the catalytic reaction mixtures under different conditions. Some ligand-stabilized Ni(ii) and Mg(ii) bimetallic species have also been identified in the ESI-MS spectra.
- Xue, Fei,Zhao, Jin,Hor, T. S. Andy
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p. 5150 - 5158
(2013/04/10)
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- One-pot synthesis of symmetrical and unsymmetrical diarylmethanes via diborylmethane
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A one-pot synthesis of diarylmethanes from air-stable diborylmethane via the Suzuki-Miyaura cross-coupling reaction is described. The present approach realizes the synthesis of various symmetrical and unsymmetrical diarylmethanes in good to excellent yields.
- Endo, Kohei,Ishioka, Takafumi,Ohkubo, Takahiro,Shibata, Takanori
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p. 7223 - 7231
(2012/10/29)
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- Nickel-mediated inter- and intramolecular reductive cross-coupling of unactivated alkyl bromides and aryl iodides at room temperature
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A nickel-mediated intermolecular reductive cross-coupling reaction of unactivated alkyl bromides and aryl iodides at room temperature has been developed and successfully extended to less explored intramolecular versions and tandem cyclization-intermolecular cross-coupling. Highly stereoselective (or stereospecific) synthesis of linear-fused perhydrofuro[2,3-b]furan (pyran) and spiroketal skeletons allows rapid access to these useful building blocks, which would be potentially valuable in the synthesis of relevant natural products. A rational explanation for the formation of contiguous stereogenic centers is given. Copyright
- Yan, Chang-Song,Peng, Yu,Xu, Xiao-Bo,Wang, Ya-Wen
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supporting information; experimental part
p. 6039 - 6048
(2012/06/18)
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- Cross-coupling of non-activated chloroalkanes with aryl grignard reagents in the presence of iron/N-heterocyclic carbene catalysts
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An efficient and high-yielding cross-coupling reaction of various primary, secondary, and tertiary alkyl chlorides with aryl Grignard reagents was achieved by using catalytic amounts of N-heterocyclic carbene ligands and iron salts. This reaction is a simple and efficient arylation method having applicability to a wide range of industrially abundant chloroalkanes, including polychloroalkanes, which are challenging substrates under conventional cross-coupling conditions.
- Ghorai, Sujit K.,Jin, Masayoshi,Hatakeyama, Takuji,Nakamura, Masaharu
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supporting information; experimental part
p. 1066 - 1069
(2012/04/10)
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- Palladium nanoparticle-cored G1-dendrimer stabilized by carbon-Pd bonds: Synthesis, characterization and use as chemoselective, room temperature hydrogenation catalyst
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Palladium nanoparticle-cored Fréchet type G1-dendrimer (Pd-G1) stabilized by Pd-carbon bonds is synthesized and characterized by IR, NMR, UV-Vis and TEM. Pd-G1 was found to be a highly efficient, chemoselective and reusable catalyst for the room temperature hydrogenation of carbon-carbon multiple bonds. Reducible functionalities like CHO, CO, COOR, CN, NO2 and halogens were unaffected. Pd-G1 is projected as an efficient catalyst for the selective hydrogenation of carbon-carbon multiple bonds in multifunctional organic molecules.
- Ratheesh Kumar, Venugopal K.,Gopidas, Karical R.
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supporting information; experimental part
p. 3102 - 3105
(2011/06/26)
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- Unsurpassed cage effect for the photolysis of dibenzyl ketones in water-soluble dendrimers
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Amphiphilic water-soluble poly(alkyl aryl ether) dendrimers Gn (n = 1-3) with charge-neutral tetraethylene glycol monomethyl ethers at their periphery were synthesized as microreactors to control the photochemical reactions of dibenzyl ketone derivatives in aqueous solutions. Photophysical studies demonstrated that Gn can encapsulate organic molecules and provide a hydrophobic microenvironment. The product distribution of photolysis of dibenzyl ketone derivatives can be successfully controlled by encapsulating the substrates within dendrimers, and an unsurpassed cage effect of 1.00 is reached in high generation dendrimers, revealing that a thick and compact "shell" was formed at the periphery of the dendrimers. The cage effect is also significantly influenced by the substituent at the para-position of the guest molecules. The higher generation dendrimers exhibit a better confined microenvironment and the aggregates possess more compact cavities to "lock" the guests than the corresponding unimolecular dendrimers. After photolysis, the separation of products can be easily achieved by extracting from the dendrimer solutions and the dendrimers are simply recovered and reused.
- Yuan, Zhao,Chen, Jinping,Zeng, Yi,Li, Ying-Ying,Han, Yongbin,Li, Yi
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p. 6256 - 6264
(2011/10/09)
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- 1, 4-butanediol as a reducing agent in transfer hydrogenation reactions
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1, 4-Butanediol is able to deliver two equivalents of H2 in hydrogen- transfer reactions to ketones, imines, and alkenes. Unlike simple alcohols, which establish equilibrium in the reduction of ketones, 1, 4-butanediol acts essentially irreversibly owing to the formation of butyrolactone, which acts as a thermodynamic sink. It is therefore not necessary to use 1, 4- butanediol in great excess in order to achieve reduction reactions. In addition, allylic alcohols are reduced to saturated alcohols through an isomerization/ reduction sequence using a ruthenium catalyst with 1, 4-butanediol as the reducing agent. Imines and alkenes are also reduced under similar conditions.
- Maytum, Hannah C.,Francos, Javier,Whatrup, David J.,Williams, Jonathan M. J.
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supporting information; experimental part
p. 538 - 542
(2010/08/06)
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- Hydrogenation of olefins using Hantzsch ester catalyzed by palladium on carbon
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Hantzsch 1,4-dihydropyridine (HEH), a well-known model compound of coenzyme NAD(P)H was found as an efficient reducing agent in hydrogenation of unactivated olefins catalyzed by Pd/C. α,β-Unsaturated ketones also underwent hydrogenation, affording the corresponding saturated ketones selectively.
- Liu, Qiang,Li, Jing,Shen, Xiao-Xia,Xing, Rui-Guang,Yang, Jie,Liu, Zhengang,Zhou, Bo
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scheme or table
p. 1026 - 1028
(2009/05/11)
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- Functional group tolerant Kumada-Corriu-Tamao coupling of nonactivated alkyl halides with aryl and heteroaryl nucleophiles: Catalysis by a nickel pincer complex permits the coupling of functionalized Grignard reagents
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A nickel(II) pincer complex [(MeNN2)NiCl] (1) catalyzes Kumada-Corriu-Tamao cross coupling of nonactivated alkyl halides with aryl and heteroaryl Grignard reagents. The coupling of octyl bromide with phenylmagnesium chloride was used as a test reaction. Using 3 mol % of 1 as the precatalyst and THF as the solvent, and in the presence of a catalytic amount of TMEDA, the coupling product was obtained in a high yield. The reaction conditions could be applied to cross coupling of other primary and secondary alkyl bromides and iodides. The coupling is tolerant to a wide range of functional groups. Therefore, alkyl halides containing ester, amide, ether, thioether, alcohol, pyrrole, indole, furan, nitrile, conjugated enone, and aryl halide moieties were coupled to give high isolated yields of products in which these units stay intact. For the coupling of ester-containing substrates, O-TMEDA is a better additive than TMEDA. The reaction protocol proves to be efficient for the coupling of Knochel-type functionalized Grignard reagents. Thus aryl Grignard reagents containing electron-deficient and/or sensitive ester, nitrile, amide, and CF3 substituents could be successfully coupled to nonactivated and functionalized alkyl iodides. The catalysis is also efficient for the coupling of alkyl iodides with functionalized heteroaryl Grignard reagents, giving rise to pyridine-, thiophene-, pyrazole-, furan-containing molecules with additional functionalities. Concerning the mechanism of the catalysis, [(MeNN2)Ni-(hetero)Ar] was identified as an intermediate, and the activation of alkyl halides was found to take place through a radical-rebound process.
- Vechorkin, Oleg,Proust, Valerie,Hu, Xile
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supporting information; experimental part
p. 9756 - 9766
(2011/03/19)
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- Suzuki-miyaura cross-coupling reactions of primary alkyltrifluoroborates with aryl chlorides
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(Chemical Equation Presented) Parallel microscale experimentation was used to develop general conditions for the Suzuki-Miyaura cross-coupling of diversely functionalized primary alkyltrifluoroborates with a variety of aryl chlorides. These conditions wer
- Dreher, Spencer D.,Lim, Siang-Ee,Sandrock, Deidre L.,Molander, Gary A.
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supporting information; experimental part
p. 3626 - 3631
(2009/09/29)
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- Palladium-catalyzed heck coupling-hydrogenation: Highly efficient one-pot synthesis of dibenzyls and alkyl phenyl esters
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An efficient method for the synthesis of industrially important dibenzyls and alkyl phenyl esters via sequential Heck coupling and hydrogenation of the alkenyl double bond in one pot with a single recyclable catalyst under mild conditions has been realised. The catalyst was recovered by simple filteration and reused for several cycles with consistent activity.
- Kantam, M. Lakshmi,Chakravarti, Rajashree,Chintareddy, Venkat Reddy,Sreedhar,Bhargava, Suresh
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supporting information; experimental part
p. 2544 - 2550
(2009/08/14)
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- Palladium-catalyzed hydroarylation of alkynes with arenediazonium salts
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The palladium-catalyzed hydroarylation of arenediazonium tetrafluoroborates with alkynes in the presence of triphenylsilane affords stereoselectively hydroarylation products in moderate to high yields. The reaction tolerates a variety of substituents including keto, ester, cyano, and nitro groups and can be performed as a one-pot procedure generating the arenediazonium salt in situ. With ethyl phenylpropynoate as the starting alkyne, the hydroarylation affords ethyl (2)-2-arylcinnamates stereo- and regioselectively.
- Cacchi, Sandro,Fabrizi, Giancarlo,Goggiamani, Antonella,Persiani, Daniela
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scheme or table
p. 1597 - 1600
(2009/04/10)
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- Methoxy-substituted stilbenes, styrenes, and 1-arylpropenes: Photophysical properties and photoadditions of alcohols
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The photochemistry of trans-stilbene and four methoxy-substituted stilbene derivatives has been investigated in a variety of solvents. The fluorescence of all five trans isomers was quenched by 2,2,2-trifluoroethanol (TFE). Upon irradiation of the five substrates in TFE, the products derived from photoaddition of the solvent were detected. Nuclear magnetic resonance spectroscopy of the products formed by irradiation in TFE-OD indicated that the proton and nucleophile are attached to two adjacent atoms of the original alkene double bond. Irradiation of the corresponding methoxy-substituted styrenes and trans-1-arylpropenes in TFE produced the analogous solvent adducts. The photoaddition of TFE proceeded with the general order of reactivity: styre > trans-1-arylpropenes > trans-stilbenes. Transient carbocation intermediates were observed following laser flash photolysis of the stilbenes in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). The results are consistent with a mechanism that involves photoprotonation of the substrates by TFE or HFIP, followed by nucleophilic trapping of short-lived carbocation intermediates. Compared to the other stilbene derivatives, trans-3,5-dimethoxystilbene displayed a large quantum yield of fluorescence and a low quantum yield of trans-cis isomerization in polar organic solvents. The unique photophysical properties of trans-3,5-dimethoxystilbene are attributed to formation of a highly polarized charge-transfer excited state (μe = 13.2 D).
- Roberts, Jeffrey C.,Pincock, James A.
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p. 1480 - 1492
(2007/10/03)
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- Stereoselective debromination and selective reduction of vic-dibromides with nickel boride
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A simple procedure is reported for the stereoselective debromination of vic-dibromides with nickel boride at ambient temperature. Debromination with concomitant reduction of vic-dibromides to give dihydro products in a one-pot reaction is also reported. α,β-Dibromoketones can also be converted to their corresponding alcohols.
- Khurana, Jitender M.,Kandpal, Bhaskar M.,Kukreja, Gagan,Sharma, Purnima
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p. 1019 - 1023
(2007/10/03)
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- Friedel-Crafts Benzylation and Phenethylation Reactions Using Benzyl and Phenethyl Benzothiazol-2-yl Carbonate Derivatives
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Friedel-Crafts benzylation and phenethylation reactions of several aromatic compounds with benzyl and phenethyl benzothiazol-2-yl carbonate derivatives were carried out in the presence of scandium triflate (Sc(OTf) 3) as a catalyst. Suitable combinations of the leaving group of carbonates and acid promoters that generate cationic alkyl species were examined.
- Mukaiyama, Teruaki,Kamiyama, Hiroaki,Yamanaka, Hiroyuki
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p. 814 - 815
(2007/10/03)
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- Selective reduction of alkynes catalyzed by palladium acetate with sodium methoxide as the hydride source
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Treatment of internal alkynes with sodium methoxide in the presence of Pd(OAc)2 and PPh3 in methanol for 48 h gave the reduction products, alkenes or alkanes in good chemical yields. This reaction proceeds through a palladium methanolate complex, followed by β-hydride elimination and reductive elimination.
- Wei, Li-Lan,Wei, Li-Mei,Pan, Wen-Bin,Leou, Shiow-Piaw,Wu, Ming-Jung
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p. 1979 - 1981
(2007/10/03)
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- New One-pot Cross-coupling Reaction between Grignard Reagents and Alkoxymethyldiphenylphosphonium Iodides in situ-Formed from Alcohols, Chlorodiphenylphosphine and Iodomethane
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A new one-pot cross-coupling reaction between Grignard reagents and alkoxymethyldiphenylphosphonium iodides, which were in situ-formed from nBuLi-treated alcohols, chlorodiphenylphosphine and iodomethane, proceeded smoothly to afford the corresponding coupling products in good to high yields.
- Shintou, Taichi,Kikuchi, Wataru,Mukaiyama, Teruaki
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p. 676 - 677
(2007/10/03)
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- B-alkyl suzuki-miyaura cross-coupling reactions with air-stable potassium alkyltrifluoroborates
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The palladium-catalyzed cross-coupling reaction of substituted potassium alkyltrifluoroborates with aryl halides and aryl triflates proceeds readily with moderate to good yields. The potassium alkyltrifluoroborates 1, 2, and 3a-e were easily synthesized and obtained as air-stable crystalline solids that can be stored for long periods of time. All of the cross-couplings proceed under the same reaction conditions using PdCl2(dppf)·CH2cl2 as catalyst in THF-H2O in the presence of 3 equiv of Cs2CO3 as base.
- Molander, Gary A.,Yun, Chang-Soo,Ribagorda, Maria,Biolatto, Betina
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p. 5534 - 5539
(2007/10/03)
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- Stable isotope labeling pattern of resveratrol and related natural stilbenes.
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The stable isotope characterization of resveratrol 1 from Polygonum cuspidatum and of related natural stilbenes 11 and 12 obtained by hydrolysis of the corresponding glucosides 2 and 3 from Rheum is reported. The C(6)-C(2)-C(6) framework of suitably protected derivatives of 1, 2, and 3 has been degraded with ozone to the C(6)-C(1) aldehydes 4, 5, 9, and 10, retaining all hydrogen atoms of the precursors. The natural and synthetic derivatives are characterized and distinguished by natural abundance deuterium nuclear magnetic resonance studies. In the case of anisaldehyde 4 the two series show, as expected, the characteristic difference of the aromatic labeling. The formyl deuterium contents of 4 and 5 from resveratrol are remarkably different, seemingly reflecting the different enrichments existing between positions 3 and 2, respectively, of the phenylpropanoid precursor. The positional delta(18)O values of the extractive materials 1-3 were also determined. In this instance a selective deoxygenation procedure was adopted, leading from 1 to the products 6, 7, and 8. The delta(18)O values of the latter compounds reveal, respectively, those at position 4' and positions 3 and 5 of 1. Similarly, the phenolic products 11 and 12 were converted into 13 and 14. From the delta(18)O values of the single components it is possible to design a detailed map of the oxygen fractionations which characterizes the stilbenes 1-3. In particular, the oxygen present at position 4' of the phenylpropanoid moiety of 1-3 shows delta(18)O values of +11.5, +1.8, and +6.7 per thousand, respectively. Moreover, the phenolic oxygen atom at position 3' of rhapontin 3 shows a value of +11.7 per thousand. The data are compared with those previously obtained on structurally related compounds. These results show the utility of simple chemical degradations in the stable isotope characterization of structurally complex food components.
- Fronza, Giovanni,Fuganti, Claudio,Serra, Stefano,Cisero, Marco,Koziet, Joseph
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p. 2748 - 2754
(2007/10/03)
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- Cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides
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The cross-coupling reactions of primary alkylboronic acids with aryl triflates and aryl halides has been successfully achieved using PdCl2(dppf)·CH2Cl2 in the presence of potassium carbonate to provide the corresponding Su
- Molander, Gary A.,Yun, Chang-Soo
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p. 1465 - 1470
(2007/10/03)
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- Radical additions to tricarbonyl[(1-4-η)-2,methoxy-5- methylenecyclohexa- 1,3-diene]iron
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Tricarbonyl[(1-4-η)-2-methoxy-5-methylenecyclohexa-1,3-diene]iron was found to undergo facile radical addition regioselectively at the exocyclic methylene group to yield aromatized product upon demetalation. (C) 2000 Elsevier Science Ltd.
- Wei, Li Lan,Lai, Ming Chih,Ong, Chi Wi
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p. 3407 - 3410
(2007/10/03)
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- Zeolite as a reagent and as a catalyst: Reduction and isomerization of alkenes by Ca Y
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Depending on the number of Bronsted acid sites present, Ca Y can act either as a reagent and reduce stilbenes to 1,2-diarylethanes or act as a catalyst and isomerize cis-stilbenes to the more stable trans form; Lewis acid sites generated by the activation process yield radical cations from stilbenes but these do not yield any stable products.
- Pitchumani,Joy, Abraham,Prevost, Nicolette,Ramamurthy
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p. 127 - 128
(2007/10/03)
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