- Palladium and Nickel Catalyzed Suzuki Cross-Coupling with Alkyl Fluorides
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Suzuki cross-coupling of benzylic and unactivated aliphatic fluorides with aryl- and alkenylboronic acids has been achieved via mechanistically distinct Pd and Ni catalyzed pathways that outperform competing protodeboronation, β-hydride elimination, and h
- Balaraman, Kaluvu,Wolf, Christian
-
supporting information
p. 8994 - 8999
(2021/11/20)
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- Relevance of Single-Transmetalated Resting States in Iron-Mediated Cross-Couplings: Unexpected Role of σ-Donating Additives
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Control of the transmetalation degree of organoiron(II) species is a critical parameter in numerous Fe-catalyzed cross-couplings to ensure the success of the process. In this report, we however demonstrate that the selective formation of a monotransmetalated FeII species during the catalytic regime counterintuitively does not alone ensure an efficient suppression of the nucleophile homocoupling side reaction. It is conversely shown that a fine control of the transmetalation degree of the transient FeIII intermediates obtained after the activation of alkyl electrophiles by a single-electron transfer (SET), achievable using σ-donating additives, accounts for the selectivity of the cross-coupling pathway. This report shows for the first time that both coordination spheres of FeII resting states and FeIII short-lived intermediates must be efficiently tuned during the catalytic regime to ensure high coupling selectivities.
- Rousseau, Lidie,Touati, Nadia,Binet, Laurent,Thuéry, Pierre,Lefèvre, Guillaume
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p. 7991 - 7997
(2021/05/26)
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- Unexpected Nickel Complex Speciation Unlocks Alternative Pathways for the Reactions of Alkyl Halides with dppf-Nickel(0)
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The mechanism of the reactions between dppf-Ni0 complexes and alkyl halides has been investigated using kinetic and mechanistic experiments and DFT calculations. The active species is [Ni(κ2-dppf)(κ1-dppf)], which undergoes a halide abstraction reaction with alkyl halides and rapidly captures the alkyl radical that is formed. The rates of the reactions of [Ni(COD)(dppf)] with alkyl halides and the yields of prototypical nickel-catalyzed Kumada cross-coupling reactions of alkyl halides are shown to be significantly improved by the addition of free dppf ligand.
- Greaves, Megan E.,Lloyd-Jones, Guy C.,Maseras, Feliu,Nelson, David J.,Ronson, Thomas O.,Sproules, Stephen
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p. 10717 - 10725
(2020/11/09)
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- General C(sp2)-C(sp3) Cross-Electrophile Coupling Reactions Enabled by Overcharge Protection of Homogeneous Electrocatalysts
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Cross-electrophile coupling (XEC) of alkyl and aryl halides promoted by electrochemistry represents an attractive alternative to conventional methods that require stoichiometric quantities of high-energy reductants. Most importantly, electroreduction can readily exceed the reducing potentials of chemical reductants to activate catalysts with improved reactivities and selectivities over conventional systems. This work details the mechanistically-driven development of an electrochemical methodology for XEC that utilizes redox-active shuttles developed by the energy-storage community to protect reactive coupling catalysts from overreduction. The resulting electrocatalytic system is practical, scalable, and broadly applicable to the reductive coupling of a wide range of aryl, heteroaryl, or vinyl bromides with primary or secondary alkyl bromides. The impact of overcharge protection as a strategy for electrosynthetic methodologies is underscored by the dramatic differences in yields from coupling reactions with added redox shuttles (generally >80%) and those without (generally 20%). In addition to excellent yields for a wide range of substrates, reactions protected from overreduction can be performed at high currents and on multigram scales.
- Hamby, Taylor B.,Sevov, Christo S.,Truesdell, Blaise L.
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supporting information
p. 5884 - 5893
(2020/04/10)
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- Photoinduced Radical Borylation of Alkyl Bromides Catalyzed by 4-Phenylpyridine
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Utilizing pyridine catalysis, we developed a visible-light-induced transition-metal-free radical borylation reaction of unactivated alkyl bromides that features a broad substrate scope and mild reaction conditions. Mechanistic studies revealed a novel nucleophilic substitution/photoinduced radical formation pathway, which could be utilized to trigger a variety of radical processes.
- Zhang, Li,Wu, Zhong-Qian,Jiao, Lei
-
supporting information
p. 2095 - 2099
(2019/12/24)
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- Nickel-catalyzed cross-coupling of umpolung carbonyls and alkyl halides
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An effective nickel-catalyzed cross-coupling of Umpolung carbonyls and alkyl halides was developed. Complementary to classical alkylation techniques, this reaction utilizes Umpolung carbonyls as the environmentally benign alkyl nucleophiles, providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Qiu, Zihang,Li, Chao-Jun
-
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- Nickel-Catalyzed Cross-Coupling of Umpolung Carbonyls and Alkyl Halides
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An effective nickel-catalyzed cross-coupling of Umpolung carbonyls and alkyl halides was developed. Complementary to classical alkylation techniques, this reaction utilizes Umpolung carbonyls as the environmentally benign alkyl nucleophiles, providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Qiu, Zihang,Li, Chao-Jun
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p. 6312 - 6322
(2019/05/24)
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- Iron-Catalyzed Suzuki-Miyaura Cross-Coupling Reactions between Alkyl Halides and Unactivated Arylboronic Esters
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An iron-catalyzed cross-coupling reaction between alkyl halides and arylboronic esters was developed that does not involve activation of the boronic ester with alkyllithium reagents nor requires magnesium additives. A combination of experimental and theoretical investigations revealed that lithium amide bases coupled with iron complexes containing deprotonated cyanobis(oxazoline) ligands were best to obtain high yields (up to 89%) in catalytic cross-coupling reactions. Mechanistic investigations implicate carbon-centered radical intermediates and highlight the critical importance of avoiding conditions that lead to iron aggregates. The new iron-catalyzed Suzuki-Miyaura reaction was applied toward the shortest reported synthesis of the pharmaceutical Cinacalcet.
- Crockett, Michael P.,Tyrol, Chet C.,Wong, Alexander S.,Li, Bo,Byers, Jeffery A.
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supporting information
p. 5233 - 5237
(2018/09/12)
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- Self-Assembly of Hierarchically Porous ZSM-5/SBA-16 with Different Morphologies and Its High Isomerization Performance for Hydrodesulfurization of Dibenzothiophene and 4,6-Dimethyldibenzothiophene
-
ZSM-5/SBA-16 (ZS) composite materials with different morphologies were synthesized successfully. The series supports were utilized to prepare NiMo/ZS for dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization (HDS) reactions. Series ZS supports and NiMo/ZS were well characterized to investigate their structure-property relationship. The NiMo/ZS catalyst (NiMo/ZS-3) with uniform morphology and well-ordered pore channels showed the maximum kHDS and TOF values of DBT and 4,6-DMDBT HDS. The kHDS value (13.9 × 10-4 mol g-1 h-1) of DBT over NiMo/ZS-3 was more than 2 times greater than that over the reference NiMo/ZS-M catalyst (5.5 × 10-4 mol g-1 h-1), 3 times greater than that over the NiMo/SBA-16 catalyst (4.4 × 10-4 mol g-1 h-1), and almost 4 times greater than that over the NiMo/ZSM-5 catalyst (3.5 × 10-4 mol g-1 h-1). Furthermore, the kHDS value (8.4 × 10-4 mol g-1 h-1) of 4,6-DMDBT over NiMo/ZS-3 was more than 3 times greater than that over the reference NiMo/ZS-M catalyst (2.8 × 10-4 mol g-1 h-1), more than 4 times greater than that over the NiMo/SBA-16 catalyst (1.7 × 10-4 mol g-1 h-1), and almost 5 times greater than that over the NiMo/ZSM-5 catalyst (1.6 × 10-4 mol g-1 h-1). The superior DBT and 4,6-DMDBT HDS performances were assigned to the uniform morphology, well-ordered pore channels, and high B/L ratio of the NiMo/ZS-3 catalyst and the suitable dispersion of the MoS2 active phases. HYD was the preferential route for DBT HDS, while ISO was the preferential route for 4,6-DMDBT HDS because of the high B/L ratio of NiMo/ZS-3. Moreover, the DBT and 4,6-DMDBT HDS reaction networks of the series NiMo/ZS are presented.
- Wang, Xilong,Mei, Jinlin,Zhao, Zhen,Zheng, Peng,Chen, Zhentao,Gao, Daowei,Fu, Jianye,Fan, Jiyuan,Duan, Aijun,Xu, Chunming
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p. 1891 - 1902
(2018/03/13)
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- Synthesis of Aryl C-Glycosides via Iron-Catalyzed Cross Coupling of Halosugars: Stereoselective Anomeric Arylation of Glycosyl Radicals
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We have developed a novel diastereoselective iron-catalyzed cross-coupling reaction of various glycosyl halides with aryl metal reagents for the efficient synthesis of aryl C-glycosides, which are of significant pharmaceutical interest due to their biological activities and resistance toward metabolic degradation. A variety of aryl, heteroaryl, and vinyl metal reagents can be cross-coupled with glycosyl halides in high yields in the presence of a well-defined iron complex, composed of iron(II) chloride and a bulky bisphosphine ligand, TMS-SciOPP. The chemoselective nature of the reaction allows the use of synthetically versatile acetyl-protected glycosyl donors and the incorporation of various functional groups on the aryl moieties, producing a diverse array of aryl C-glycosides, including Canagliflozin, an inhibitor of sodium-glucose cotransporter 2 (SGLT2), and a prevailing diabetes drug. The cross-coupling reaction proceeds via generation and stereoselective trapping of glycosyl radical intermediates, representing a rare example of highly stereoselective carbon-carbon bond formation based on iron catalysis. Radical probe experiments using 3,4,6-tri-O-acetyl-2-O-allyl-α-d-glucopyranosyl bromide (8) and 6-bromo-1-hexene (10) confirm the generation and intermediacy of the corresponding glycosyl radicals. Density functional theory (DFT) calculations reveal that the observed anomeric diastereoselectivity is attributable to the relative stability of the conformers of glycosyl radical intermediates. The present cross-coupling reaction demonstrates the potential of iron-catalyzed stereo- and chemoselective carbon-carbon bond formation in the synthesis of bioactive compounds of certain structural complexity.
- Adak, Laksmikanta,Kawamura, Shintaro,Toma, Gabriel,Takenaka, Toshio,Isozaki, Katsuhiro,Takaya, Hikaru,Orita, Akihiro,Li, Ho C.,Shing, Tony K. M.,Nakamura, Masaharu
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p. 10693 - 10701
(2017/08/15)
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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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- Photoredox-Assisted Reductive Cross-Coupling: Mechanistic Insight into Catalytic Aryl-Alkyl Cross-Couplings
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Here, we describe a photoredox-assisted catalytic system for the direct reductive coupling of two carbon electrophiles. Recent advances have shown that nickel catalysts are active toward the coupling of sp3-carbon electrophiles and that well-controlled, light-driven coupling systems are possible. Our system, composed of a nickel catalyst, an iridium photosensitizer, and an amine electron donor, is capable of coupling halocarbons with high yields. Spectroscopic studies support a mechanism where under visible light irradiation the Ir photosensitizer in conjunction with triethanolamine are capable of reducing a nickel catalyst and activating the catalyst toward cross-coupling of carbon electrophiles. The synthetic methodology developed here operates at low 1 mol % catalyst and photosensitizer loadings. The catalytic system also operates without reaction additives such as inorganic salts or bases. A general and effective sp2-sp3 cross-coupling scheme has been achieved that exhibits tolerance to a wide array of functional groups.
- Paul, Avishek,Smith, Mark D.,Vannucci, Aaron K.
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p. 1996 - 2003
(2017/02/26)
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- Mechanistic Studies of Catalytic Carbon-Carbon Cross-Coupling by Well-Defined Iron NHC Complexes
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The mechanism of iron-catalyzed carbon-carbon cross-coupling reactions between Grignard reagents and alkyl halides has been investigated using well-defined N-heterocyclic carbene (NHC) compounds. The iron(II) precatalyst, [Fe2Cl2(μ-Cl)2(IPr)2], was employed in several C-C cross coupling reactions exhibiting the ability to efficiently couple primary and secondary alkyl halides with several aryl and alkyl Grignard reagents. For selected substrates, a 2 mol % catalyst loading (4 mol % Fe) afforded conversions of >99% and were achieved with 8% homocoupling of the electrophile. The mechanism of the coupling reaction was studied by means of radical clock, radical trap, and single-turnover experiments, which support a radical-based cycle involving an Fe(II/III) redox couple. The implications of this mechanism on the efficacy of iron-NHC-catalyzed cross-coupling reactions are discussed.
- Przyojski, Jacob A.,Veggeberg, Kevin P.,Arman, Hadi D.,Tonzetich, Zachary J.
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p. 5938 - 5946
(2015/10/12)
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- Hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and their hydrogenated intermediates over bulk tungsten phosphide
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The kinetics of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and their hydrogenated intermediates over bulk tungsten phosphide (WP) was studied. WP possessed high hydrogenation/dehydrogenation activity but was highly sensitive to piperidine inhibition. 4,6-DMDBT reacted faster than DBT, and both DBT and 4,6-DMDBT reacted mainly through the hydrogenation pathway. The methyl groups suppressed the direct desulfurization of 4,6-DMDBT but significantly promoted the hydrogenation of 4,6-DMDBT and the dehydrogenation of 1,2,3,4-tetrahydro-4,6-dimethyldibenzothiophene (TH-4,6-DMDBT) and 1,2,3,4,4a,9b-hexahydro-4,6-dimethyldibenzothiophene, but decreased the rate of hydrogenation of TH-4,6-DMDBT. Piperidine inhibited the HDS of 4,6-DMDBT much more strongly than that of DBT. Substantial dehydrogenation of TH-4,6-DMDBT to 4,6-DMDBT and two of its isomers occurred. The formation of these 4,6-DMDBT isomers in the dehydrogenation of TH-4,6-DMDBT and the hydrocracking of 1-methyl-4-(3-methylcyclohexyl)-benzene, as well as the formation of cyclopentylphenylmethane and (cyclopentylmethyl)cyclohexane, is ascribed to the metallic character of WP.
- Yang, Lei,Li, Xiang,Wang, Anjie,Prins, Roel,Chen, Yongying,Duan, Xinping
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p. 330 - 343
(2015/09/01)
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- Iron pincer complexes as catalysts and intermediates in alkyl-aryl kumada coupling reactions
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Iron-catalyzed alkyl-aryl Kumada coupling has developed into an efficient synthetic method, yet its mechanism remains vague. Here, we apply a bis(oxazolinylphenyl)amido pincer ligand (Bopa) to stabilize the catalytically active Fe center, resulting in isolation and characterization of well-defined iron complexes whose catalytic roles have been probed and confirmed. Reactivity studies of the iron complexes identify an Fe(II) "ate" complex, [Fe(Bopa-Ph)(Ph)2]-, as the active species for the oxidative addition of alkyl halide. Experiments using radical-probe substrates and DFT computations reveal a bimetallic and radical mechanism for the oxidative addition. The kinetics of the coupling of an alkyl iodide with PhMgCl suggests that formation of the "ate" complex, rather than oxidative addition, is the turnover-determining step. This work provides insights into iron-catalyzed cross-coupling reactions of alkyl halides.
- Bauer, Gerald,Wodrich, Matthew D.,Scopelliti, Rosario,Hu, Xile
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supporting information
p. 289 - 298
(2015/01/30)
-
- Expedient iron-catalyzed coupling of alkyl, benzyl and allyl halides with arylboronic esters
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While attractive, the iron-catalyzed coupling of arylboron reagents with alkyl halides typically requires expensive or synthetically challenging diphosphine ligands. Herein, we show that primary and secondary alkyl bromides and chlorides, as well as benzyl and allyl halides, can be coupled with arylboronic esters, activated with alkyllithium reagents, by using very simple iron-based catalysts. The catalysts used were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)3] with no added co- ligands. In the former case, preliminary mechanistic studies highlight the likely involvement of iron(I)-phosphine intermediates. More irons in the fire: Primary and secondary alkyl, benzyl and allyl halides were coupled with arylboronic esters by using very simple iron-based catalysts. These were either adducts of inexpensive and widely available diphosphines or, in a large number of cases, simply [Fe(acac)3] with no added co-ligands (see scheme; acac=acetylacetonate). In the former case, preliminary mechanistic studies highlight the likely involvement of low-coordinate iron(I)-phosphine intermediates.
- Bedford, Robin B.,Brenner, Peter B.,Carter, Emma,Carvell, Thomas W.,Cogswell, Paul M.,Gallagher, Timothy,Harvey, Jeremy N.,Murphy, Damien M.,Neeve, Emily C.,Nunn, Joshua,Pye, Dominic R.
-
supporting information
p. 7935 - 7938
(2014/07/07)
-
- Suzuki-miyaura cross-coupling reactions of unactivated alkyl halides catalyzed by a nickel pincer complex
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A nickel(II) pincer complex, [(MeN2N)Ni-Cl], was used to catalyze alkyl-alkyl and alkyl-aryl Suzuki-Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups. Georg Thieme Verlag Stuttgart, New York.
- Di Franco, Thomas,Boutin, Nicolas,Hu, Xile
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p. 2949 - 2958
(2013/11/06)
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- Mechanism and selectivity in nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides
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The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides with alkyl halides and demonstrate that the selectivity arises from an unusual catalytic cycle that combines both polar and radical steps to form the new C-C bond.
- Biswas, Soumik,Weix, Daniel J.
-
supporting information
p. 16192 - 16197
(2013/11/19)
-
- Synthesis and hydrodesulfurization properties of NiW catalyst supported on high-aluminum-content, highly ordered, and hydrothermally stable Al-SBA-15
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Highly ordered mesoporous Al-SBA-15 with high aluminum content and high hydrothermal stability has been synthesized by a new pH-adjusting and high-temperature hydrothermal treatment approach. Thus-prepared samples were characterized by X-ray fluorescence spectroscopy, X-ray powder diffraction, 27Al nuclear magnetic resonance spectroscopy, N2 adsorption-desorption, temperature-programmed desorption of ammonia, Fourier transformed infrared spectroscopy with pyridine adsorption, temperature- programmed reduction with hydrogen, and high-resolution transmission electron microscopy. The results showed that Al-SBA-15 had high aluminum loading (with its molar Si/Al ratio of 5.1, similar to that of the initial gel mixture) and homogenously distributed Al species in the walls. Moreover, the product showed extremely high hydrothermal stability (with only a 15.2% decrease in surface area after steaming at 800 °C for 5 h) and moderate acidity. An Al-SBA-15-supported NiW hydrodesulfurization catalyst was prepared and evaluated using dibenzothiophene hydrodesulfurization. Compared with γ-Al 2O3- and SBA-15-supported catalysts, the Al-SBA-15-supported NiW catalyst showed outstanding hydrodesulfurization activity.
- Li, Yang,Pan, Dahai,Yu, Chengzhong,Fan, Yu,Bao, Xiaojun
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experimental part
p. 124 - 136
(2012/03/11)
-
- Synthesis of iron(III) complex bearing tridentate β-Aminoketonato Ligand: Application to iron-catalyzed cross-coupling reaction of arylmagnesium bromides with alkyl halides
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A tridentate β-aminoketonato iron complex was prepared by the reaction of lithium β-aminoketonato with FeCl3. This iron complex was found to be an efficient catalyst for the crosscoupling reaction between arylmagnesium bromides and alkyl halides.
- Yamaguchi, Yoshitaka,Ando, Hiroaki,Nagaya, Makoto,Hinago, Hideto,Ito, Takashi,Asami, Masatoshi
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supporting information; experimental part
p. 983 - 985
(2011/12/05)
-
- Vanadium-catalyzed cross-coupling reactions of alkyl halides with aryl grignard reagents
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Vanadium(III) chloride catalyzed cross-coupling reactions of alkyl halides with arylmagnesium bromides. Various arylmagnesium bromides, except for an ortho-substituted arylmagnesium reagent, could be used for the reaction. Among alkyl halides tested, cyclohexyl halides and primary alkyl halides were good substrates. The reactions likely proceed via carbon-centered radical intermediates. 2008 The Chemical Society of Japan.
- Yasuda, Shigeo,Yorimitsu, Hideki,Oshima, Koichiro
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experimental part
p. 287 - 290
(2009/03/12)
-
- Iron nanoparticles in the coupling of alkyl halides with aryl Grignard reagents
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Iron nanoparticles, either formed in situ stabilized by 1,6-bis(diphenylphosphino)hexane or polyethylene glycol (PEG), or preformed stabilized by PEG, are excellent catalysts for the cross-coupling of aryl Grignard reagents with primary and secondary alkyl halides bearing β-hydrogens and they also prove effective in a tandem cyclization/cross- coupling reaction. The Royal Society of Chemistry 2006.
- Bedford, Robin B.,Betham, Michael,Bruce, Duncan W.,Davis, Sean A.,Frost, Robert M.,Hird, Michael
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p. 1398 - 1400
(2008/02/03)
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- Simple iron-amine catalysts for the cross-coupling of aryl Grignards with alkyl halides bearing β-hydrogens
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Mixtures of iron(III) chloride and appropriate amine ligands are active catalysts for the coupling of aryl Grignard reagents with primary and secondary alkyl halide substrates bearing β-hydrogens, under mild and simple reaction conditions. The Royal Society of Chemistry 2005.
- Bedford, Robin B.,Bruce, Duncan W.,Frost, Robert M.,Hird, Michael
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p. 4161 - 4163
(2007/10/03)
-
- Tandem intramolecular carbolithiation-transmetallation: From lithium to copper or boron chemistry
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Lithium/copper transmetallation from the organolithium intermediate 3 (obtained via intramolecular carbolithiation of the acyclic organolithium 2, generated by a chlorine-lithium exchange) gives the corresponding organocopper intermediate 5. This intermediate reacts with eletrophiles, such as allylic or propargylic halides, acyl chlorides or α,β-unsaturated carbonyl compounds giving the expected compounds 6-10, which are not possible to be obtained directly from the organolithium 3. On the other hand, lithium/boron transmetallation affords the corresponding alkylboronic acid 11 which, after palladium-catalysed Suzuki-Miyaura cross-coupling reaction with different aryl bromides gives the expected products 12 with modest yields, the corresponding Ullman biarylic homocoupling products being the major by-products.
- Ortiz, Rosa,Yus, Miguel
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p. 1699 - 1707
(2007/10/03)
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- Tandem intramolecular carbolithiation-lithium/zinc transmetallation and applications to carbon-carbon bond-forming reactions
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Lithium/zinc transmetallation with the cyclic organolithium intermediate 3 (prepared by intramolecular carbolithiation of the initially formed organolithium 2) gives the corresponding organozinc intermediate 5. Copper- or palladium-promoted SN2
- Yus, Miguel,Ortiz, Rosa
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p. 3833 - 3841
(2007/10/03)
-
- Iron-Catalyzed Cross-Coupling of Primary and Secondary Alkyl Halides with Aryl Grignard Reagents
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An iron-catalyzed cross-coupling reaction of a primary or secondary alkyl halide with an aryl Grignard reagent proceeds under mild conditions to give the corresponding coupling product in quantitative yield. Copyright
- Nakamura, Masaharu,Matsuo, Keiko,Ito, Shingo,Nakamura, Eiichi
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p. 3686 - 3687
(2007/10/03)
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- Intramolecular carbolithiation promoted by a DTBB-catalysed chlorine-lithium exchange
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The reaction of 6-chlorohex-1-ene 1 with lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5% molar) in THF at -78°C gives the corresponding organolithium intermediate 2, which by reaction with different electrophiles affords, aft
- Yus, Miguel,Ortiz, Rosa,Huerta, Fernando F.
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p. 8525 - 8542
(2007/10/03)
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- Palladium-catalyzed homocoupling reactions between two Csp3-Csp3 centers
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(Matrix Presented) A novel palladium-catalyzed coupling reaction between two Csp3-Csp3 centers has been investigated. This protocol is initiated by the oxidative addition of an α-halo carbonyl compound to a palladium(0) species, followed by the double transmetalation. The key dialkyl palladium intermediate undergoes reductive elimination to form the desired coupling product.
- Lei, Aiwen,Zhang, Xumu
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p. 2285 - 2288
(2007/10/03)
-
- Radical reactions in organoboron chemistry II - Inter- and intramolecular addition of carbon centered radicals to alkenylboranes
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The intermolecular addition of carbon centered radicals to alkenylboranes has been studied. The influence of the olefin and boron substituents on the reactivity and the regioselectivity was determined. Competitive experiments were carried out to estimate the relative reactivity of a series of vinylboranes and other electron deficient alkenes. Intramolecular versions of these additions were also described as well as some further transformations of selected adducts.
- Guennouni,Lhermitte,Cochard,Carboni
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p. 6999 - 7018
(2007/10/02)
-
- Anionic cyclization of olefinic alkyllithiums: Ring closure of terminally substituted 5-hexenyllithiums
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A series of 5-hexenyllithiums having a phenyl, trimethylsilyl, or cyclopropyl substituent at the terminal [C(6)] alkene carbon have been prepared from the corresponding iodides by lithium-iodine exchange with t-butyllithium at -78°C. Although 6-alkyl-substituted 5-hexenyllithiums do not isomerize to five-membered rings upon warning, terminally substituted 5-hexenyllithiums bearing a moderately activating phenyl or trimethylsilyl group cleanly undergo a totally regiospecific 5-exo cyclization at sub-ambient temperatures to afford five membered rings bearing a CHRLi moiety that may be trapped with an electrophile to deliver high yields of functionalized product. Cyclization of 6-cyclopropyl-5-hexenyllithium is accompanied by ring opening of the three-membered ring.
- Bailey, William F.,Gavaskar, Kaustubh V.
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p. 5957 - 5970
(2007/10/02)
-
- Synthesis and evaluation of 4-alkylanilines as mammary tumor inhibiting aromatase inhibitors
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The 4-alkylanilines 1-20 were synthesized to elucidate the importance of the glutarimide moiety for the aromatase inhibiting activity of aminoglutethimide [3-(4-aminophenyl)-3-ethylpiperidine-2,6-dione, AG], the only non-steroidal aromatase inhibitor which is commercially available at present. The most interesting compounds were the (4-aminophenyl)cycloalkanes 4-6 (4, c-pentyl; 5, c-hexyl; 6, c-heptyl) and the 1-alkyl-1-(4-aminophenyl)cyclohexanes 1-3 (1, CH3; 2, C2H5; 3, n-C3H7). Derivatives 1-6 are stronger inhibitors of human placental aromatase than AG exhibiting relative potencies from 1.5 to 2.7 (AG≡1). For selectivity of action, the inhibition of desmolase (cholesterol side chain cleavage enzyme) was determined. Compounds 1-3 showed an inhibition comparable to AG, whereas compounds 4-6 exhibited no effect on desmolase. Being more potent and selective aromatase inhibitors in vitro, compounds 4-6, however, were not superior to AG in vivo, when the reduction of plasma estradiol concentration and the tumor inhibiting activity (PMSG-primed SD rats and DMBA-induced mammary carcinoma of the SD rat, postmenopausal model) were concerned.
- Hartmann,Batzl
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p. 537 - 544
(2007/10/02)
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- Acid-catalyzed Reactions of Aromatic Hydrocarbons with Alkanes and Cycloalkanes. X. Alkylations with Cyclohexane
-
The complex reaction mixtures of the nonconventional alkylation of benzene with cyclohexane in the presence of Lewis/proton acids and promotors were investigated by gas-liquid chromatography and mass spectrometry.Four representative groups of hydrocarbons were found including cycloalkylbenzenes, substituted indanes or tetralines (C12H16), C1-C6-alkylbenzenes and isomeric biscycloalkyls (C12H22).Their formation is interpreted as a competition between alkylation, (without or with isomerization), ringfission with cycloalkylation or fragmentation, and self-alkylation; phenylcycloalkylcations and phenylalkylcations are the intermediates.
- Miethchen, Ralf,Steege, Sigrid,Kroeger, Carl-Friedrich
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p. 823 - 834
(2007/10/02)
-
- Novel phenylacetic acid derivatives
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Phenylacetic acid derivatives of the formula STR1 wherein n is an integer of 2 to 5; STR2 R1 is hydrogen, halogen, trifluoromethyl, nitro or amino; R2 and R3 each independently is hydrogen or lower alkyl; or together form an ethylene group; X1 represents two hydrogen atoms or an oxo group; and Y1 is cyano, hydroxyamidocarbonyl, carbamoyl, 5-tetrazolyl or carboxyl; and for derivatives wherein Y is carboxyl, salts thereof with physiologically compatible bases, esters thereof from physiologically acceptable alcohols and amides thereof from physiologically acceptable amines have valuable pharmacological activity, e.g., as antiinflammatory agents.
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