- Mechanistic studies into visible light-driven carboxylation of aryl halides/triflates by the combined use of palladium and photoredox catalysts
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The reaction mechanism of palladium-catalyzed visible light-driven carboxylation of aryl halides and triflates with a photoredox catalyst was examined in detail. Experimental and theoretical studies indicated that the active species for photoredox- catalyzed reduction was cationic ArPd(II)+ species to generate nucleophilic ArPd(I) or its further reduced ArPd(0)- species, which reacted with CO2 to give carboxylic acids. Hydrodehalogenated compounds, main byproducts in this carboxylation, were thought to be generated by protonation of these reduced species.
- Caner, Joaquim,Iwasawa, Nobuharu,Martin, Ruben,Murata, Kei,Shimomaki, Katsuya,Toriumi, Naoyuki
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supporting information
p. 1846 - 1853
(2021/08/13)
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- Copper-catalysed low-temperature water-gas shift reaction for selective deuteration of aryl halides
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The introduction of deuterium atoms into organic compounds is of importance for basic chemistry, material sciences, and the development of drugs in the pharmaceutical industry, specifically for identification and quantification of metabolites. Hence, methodologies for the synthesis of selectively labelled compounds continue to be a major area of interest for many scientists. Herein, we present a practical and stable heterogeneous copper catalyst, which permits for dehalogenative deuterationviawater-gas shift reaction at comparably low temperature. This novel approach allows deuteration of diverse (hetero)aryl halides with good functional group tolerance, and no reduction of the aromatic rings or other easily reducible formyl and cyano groups. Multi-gram experiments show the potential of this method in organic synthesis and medicinal chemistry.
- Bartling, Stephan,Beller, Matthias,Bourriquen, Florian,Junge, Kathrin,Li, Wu,Liu, Weiping,Qu, Ruiyang,Rockstroh, Nils
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p. 14033 - 14038
(2021/11/12)
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- Radical-Mediated Cascade Spirocyclization of N-Benzylacrylamides with Polyhaloalkanes: Access to Polyhalo-Substituted Azaspirocyclohexadienones
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A novel and mild metal-free catalyzed radical-mediated cascade spirocyclization of N-benzylacrylamides with polyhaloalkanes is proposed for the preparation of polyhalo-substituted azaspirocyclohexadienones. Notably, polyhaloalkanes are employed as efficie
- Hu, Yun-Chu,Long, Fang,Peng, Chuan-Chong,Wang, Ru,Wu, Li-Jun,Xiao, Hong-Bo,Ye, Meng-Hua,Zhang, Kai-Yi,Zhou, Zheng-Rui
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supporting information
(2022/02/14)
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- Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes
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A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]?- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.
- Tian, Ya-Ming,Guo, Xiao-Ning,Krummenacher, Ivo,Wu, Zhu,Nitsch, J?rn,Braunschweig, Holger,Radius, Udo,Marder, Todd B.
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supporting information
p. 18231 - 18242
(2020/11/02)
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- Pt-Pd nanoalloy for the unprecedented activation of carbon-fluorine bond at low temperature
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Carbon-fluorine bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that has hitherto often required harsh conditions. The alloying of Pt with Pd is crucial to promote the overall C-F bond. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond cleavage. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction.
- Dhital, Raghu Nath,Ehara, Masahiro,Haesuwannakij, Setsiri,Nomura, Keigo,Sakurai, Hidehiro,Sato, Yoshinori
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p. 1180 - 1185
(2020/10/18)
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- Cp2TiCl2-Catalyzed Carboxylation of Aryl Chlorides with Carbon Dioxide in the Presence of n-BuMgCl
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Cp2TiCl2-catalyzed carboxylation of aryl chlorides with carbon dioxide to afford benzoic acids in good yields has been achieved in the presence of n-BuMgCl. The reaction proceeds by a sequential magnesium halide exchange reaction and carboxylation with CO2 in a wide variety of aryl chlorides under mild conditions.
- Hang, Wei,Yi, Yaping,Xi, Chanjuan
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supporting information
p. 1476 - 1479
(2020/01/21)
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- Hydro/deutero deamination of arylazo sulfones under metal and (photo)catalyst-free conditions
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Hydrodeaminated and monodeuterated aromatics were obtained via a visible-light driven reaction of arylazo sulfones. Deuteration occurs efficiently in deuterated media such as isopropanol-d8 or in THF-d8/water mixtures and exhibits a high tolerance to the nature and the position of the aromatic substituents.
- Amin, Hawraz I.M.,Raviola, Carlotta,Amin, Ahmed A.,Mannucci, Barbara,Protti, Stefano,Fagnoni, Maurizio
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- Visible-Light-Induced Organocatalytic Borylation of Aryl Chlorides
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The preparation of arylboronates from unactivated aryl chlorides in a transition-metal-free manner is rather challenging. There are only few examples to achieve this goal by using ultraviolet irradiation. Based on the mechanistic understanding of the diboron/methoxide/pyridine reaction system, we achieved photoactivation of the in situ generated super electron donor and developed a visible-light-induced organocatalytic method for efficient borylation of unactivated aryl chlorides.
- Zhang, Li,Jiao, Lei
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supporting information
p. 9124 - 9128
(2019/06/17)
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- Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
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Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the kinetics of base-catalyzed protodeboronation of 30 different arylboronic acids has now been determined at pH > 13 in aqueous dioxane at 70 °C. Included in the study are all 20 isomers of C6HnF(5-n)B(OH)2 with half-lives spanning 9 orders of magnitude: a and Sδ values, kinetic isotope effects (2H, 10B, 13C), linear free-energy relationships, and density functional theory calculations, we have identified a mechanistic regime involving unimolecular heterolysis of the boronate competing with concerted ipso protonation/C-B cleavage. The relative Lewis acidities of arylboronic acids do not correlate with their protodeboronation rates, especially when ortho substituents are present. Notably, 3,5-dinitrophenylboronic acid is orders of magnitude more stable than tetra-and pentafluorophenylboronic acids but has a similar pKa.
- Cox, Paul A.,Reid, Marc,Leach, Andrew G.,Campbell, Andrew D.,King, Edward J.,Lloyd-Jones, Guy C.
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supporting information
p. 13156 - 13165
(2017/09/26)
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- Metal-free radical aromatic carbonylations mediated by weak bases
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We report a new method of metal-free alkoxycarbonylation. This reaction involves the generation of aryl radicals from arenediazonium salts by a very weak base (HCO2Na) under mild conditions. Subsequent radical trapping with carbon monoxide and alcohols gives alkyl benzoates. The conditions (metal-free, 1 equiv. base, MeCN, r.t., 3 h) tolerate various functional groups (I, Br, Cl, CF3, SF5, NO2, ester). Mechanistic studies indicate the operation of a radical aromatic substitution mechanism.
- Koziakov, Denis,Jacobi Von Wangelin, Axel
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supporting information
p. 6715 - 6719
(2017/08/22)
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- Transition-metal-free dehalogenation of aryl halides promoted by phenanthroline/potassium tert-butoxide
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Transition-metal-free dehalogenation of various aryl halides (iodides and bromides) can take place efficiently at 70–110?°C in the presence of a catalytic amount of 1, 10-phenanthroline and t-BuOK using THF or Dioxane as solvent. Control experiments indicated that radical transfer occurred between aryl radical and alkyl C[sbnd]H bond to generate alkyl radical.
- Liu, Wei,Hou, Fanyi
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p. 931 - 937
(2017/01/25)
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- N-Methylanilines as Simple and Efficient Promoters for Radical-Type Cross-Coupling Reactions of Aryl Iodides
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Activation of the carbon–halogen bonds in aryl halides is a key step in transition-metal-free cross-coupling reactions. In this paper, a new and efficient radical initiation system for the activation of iodoarenes to produce aryl radicals was discovered, which employs the combination of N-methylanilines and tBuOK. This radical initiation system is robust and versatile, enabling various types of aryl-radical-related reactions.
- Yang, Huan,Zhang, Li,Jiao, Lei
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supporting information
p. 65 - 69
(2017/01/09)
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- Revisiting the Radical Initiation Mechanism of the Diamine-Promoted Transition-Metal-Free Cross-Coupling Reaction
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Radical chain reactions leading to C-C bond formation are widely used in organic synthesis, and initiation of the radical chain process usually requires thermolabile radical initiators. Recent studies on transition-metal-free cross-coupling reactions between aryl halides and arenes have demonstrated an unprecedented initiation system for radical chain reactions, where the combination of simple organic additives and a base was used in place of conventional radical initiators. Among them, the combination of N,N′-dimethylethylenediamine (DMEDA) and t-BuOK is one of the most efficient and representative reaction systems, and the radical initiation mechanism of this system has attracted considerable research interest. In this study, through the combination of kinetic studies, deuterium labeling experiments, and DFT calculations, the radical initiation mechanism of the diamine-promoted cross-coupling reaction was carefully reinvestigated. In light of the present study, a mechanistic network of radical initiation in the DMEDA/t-BuOK system was revealed, which differs dramatically from the previously realized single radical initiation pathway. In this mechanism, the diamine acts as a hydrogen atom donor and plays a dual role as both "radical amplifier" and "radical regulator" to initiate the radical chain process as well as to control the concentration of reactive radical species. This represents a rare example of a structurally simple molecule playing such a subtle role in the radical chain reaction system. The present study sheds some light on the novel radical initiation mode in transition-metal-free cross-coupling reactions following a base-promoted homolytic aromatic substitution (BHAS) mechanism, and may also help to understand the mechanism of relevant reactions.
- Zhang, Li,Yang, Huan,Jiao, Lei
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supporting information
p. 7151 - 7160
(2016/07/06)
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- Metal-Free sp2-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes
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C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp2-C-H bond and intramolecular protonation of the sp2-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes.
- Chernichenko, Konstantin,Lindqvist, Markus,Kótai, Bianka,Nieger, Martin,Sorochkina, Kristina,Pápai, Imre,Repo, Timo
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p. 4860 - 4868
(2016/05/10)
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- Visible-light-facilitated 5-exo-trig cyclization of 1,6-dienes with alkyl chlorides: Selective scission of the C(sp3)-H bond in alkyl chlorides
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A general and conceptually novel method for preparing polychloro- substituted pyrrolidin-2-ones and indeno[2,1-c]pyrrol-3(3aH)-ones is established by visible-light-facilitated 5-exo-trig cyclization of 1,6-dienes with alkyl chlorides through selectively splitting the C(sp3)-H bond adjacent to the chloride atom to form an alkyl radical. The 5-exo-trig cyclization of 1,6-dienes with alkyl chlorides through a visible-light-facilitated radical strategy is presented. This is achieved by selectively splitting the C(sp 3)-H bond adjacent to the chloride atom to form an alkyl radical. bpy = 2,2′-bipyridyl. Copyright
- Liu, Yu,Zhang, Jia-Ling,Song, Ren-Jie,Li, Jin-Heng
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p. 1177 - 1181
(2014/03/21)
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- Pd-PEPPSI-type expanded ring N-heterocyclic carbene complexes: Synthesis, characterization, and catalytic activity in Suzuki-Miyaura cross coupling
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The synthesis and characterization of the new six- and seven-membered Pd-PEPPSI-type N-heterocyclic carbene (NHC) complexes 3 and 4 is described. Complexes of the general formula [Pd(NHC)(3ClPy)Cl2] (NHC = 6- or 7-Mes, 3ClPy = 3-chloropyridine) are accessed via the oxidation of the well-defined parent palladium(0) complexes 1 and 2. Complexes 3 and 4 have been employed in Suzuki-Miyaura cross-coupling and catalytic dehalogenation of a range of aryl halide substrates.
- Dunsford, Jay J.,Cavell, Kingsley J.
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supporting information
p. 2902 - 2905
(2014/06/24)
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- Visible-Light-Facilitated 5-exo-trig Cyclization of 1,6-Dienes with Alkyl Chlorides: Selective Scission of the C(sp3)-H Bond in Alkyl Chlorides
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A general and conceptually novel method for preparing polychloro-substituted pyrrolidin-2-ones and indeno[2,1-c]pyrrol-3(3aH)-ones is established by visible-light-facilitated 5-exo-trig cyclization of 1,6-dienes with alkyl chlorides through selectively splitting the C(sp3)-H bond adjacent to the chloride atom to form an alkyl radical.
- Liu, Yu,Zhang, Jia-Ling,Song, Ren-Jie,Li, Jin-Heng
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p. 1177 - 1181
(2015/10/05)
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- Kinetic study of the 7- endo selective radical cyclization of N-tert-butyl-o-bromobenzylmethacryl amides: Kinetic investigation of the cyclization and 1,7-hydrogen transfer of aromatic radicals
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A kinetic investigation of the radical cyclization of N-tert-butyl-o- bromobenzylmethacryl amides to give 2-benzazepines via 7-endo selective cyclization was undertaken. The aryl radical generated from the amide precursor by treatment with Bu3SnH gave the three compounds, which are a 7-endo cyclized adduct, a 6-exocyclized adduct, and a reduced product. The cyclization reactions under various Bu3SnH concentrations were traced by GC analysis. The 7-endo/6-exo selectivity was constant irrespective of variation in Bu3SnH concentration. These results revealed that regioselectivity is controlled in a kinetic manner and that there is no possibility of a neophyl rearrangement. The use of Bu3SnD revealed that 1,7-hydrogen transfer, in which an aryl radical abstracts a hydrogen atom from the methallylic methyl group, occurs during the reaction. Hydrogen abstraction from toluene, the reaction solvent, was also observed. The 1,7-transfer rate depended on the Bu3SnX (X = H or D), and the reaction kinetics was examined. The kH/kD value for the hydrogen abstraction of aryl radical from Bu3SnX (X = H or D) was estimated using 4-bromoanisol. The utilization of these values revealed the overall reaction kinetics and relative rates for the cyclization and reduction by Bu3SnX (X = H or D). Kinetic parameters for hydrogen abstraction from toluene by aryl radicals were also estimated.
- Kamimura, Akio,Kotake, Tomoko,Ishihara, Yuriko,So, Masahiro,Hayashi, Takahiro
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p. 3961 - 3971
(2013/05/22)
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- β-Arylation of carboxamides via iron-catalyzed C(sp3)-H bond activation
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A 2,2-disubstituted propionamide bearing an 8-aminoquinolinyl group as the amide moiety can be arylated at the β-methyl position with an organozinc reagent in the presence of an organic oxidant, a catalytic amount of an iron salt, and a biphosphine ligand at 50 C. Various features of selectivity and reactivity suggest the formation of an organometallic intermediate via rate-determining C-H bond cleavage rather than a free-radical-type reaction pathway.
- Shang, Rui,Ilies, Laurean,Matsumoto, Arimasa,Nakamura, Eiichi
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supporting information
p. 6030 - 6032,3
(2013/05/22)
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- Nickel-catalyzed hydrodehalogenation of aryl halides
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In the present study, the nickel-catalyzed dehalogenation of aryl and alkyl halides with iso-propyl zinc bromide or tert-butylmagnesium chloride has been examined in detail. With a straightforward nickel complex as pre-catalyst good to excellent yields and chemoselectivities were feasible for a variety of aryl and alkyl halides.
- Weidauer, Maik,Irran, Elisabeth,Someya, Chika I.,Haberberger, Michael,Enthaler, Stephan
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supporting information
p. 53 - 59
(2013/08/25)
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- Nickel complexes catalyzed hydrodechlorination of aryl chlorides in ionic liquid
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The hydrodechlorination performance of nickel complex catalysts, Ni[phen]2(PF6)2 and Ni[bpy]3(PF 6)2, were investigated with [Bmim]Br as the ionic liquid solvent. It is proved that Ni[phen]2(PF6)2 is efficient for the hydrodechlorination of aryl chlorides under mild conditions with water as the hydrogen source. The hydrogen source of reaction is from the water which was confirmed by the deuterium incorporation experiments. Recycling experiments showed a decreasing activity of this catalyst due to a small leaching of nickel complex from the ionic liquid phase during the recycling process where n-heptane was used as the extractant. A plausible reaction route has been suggested.
- Sun, Guanghui,Zhang, Lirong,Zhang, Guanlin,Fan, Yuehui,Wang, Yuhong,Lu, Guanzhong
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p. 1365 - 1370
(2014/04/17)
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- Halogen-deuterium exchange reaction mediated by tributyltin hydride using THF-d8 as the deuterium source
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A regioselective deuteration method for a wide variety of aromatic compounds using the halogen-deuterium exchange reaction initiated by Bu 3SnH using THF-d8 as the deuterium source was developed.
- Mutsumi, Tomonobu,Iwata, Hiroki,Maruhashi, Kazuo,Monguchi, Yasunari,Sajiki, Hironao
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experimental part
p. 1158 - 1165
(2011/03/22)
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- A gallium-catalyzed cycloisomerization/Friedel-Crafts tandem
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Under noble (Au, Pt, Ru) and group 13 (Ga, In) metals catalysis, 1,6-arenynes rearrange to give 1,2-dihydronaphthalenes in a high yielding, regiocontrolled fashion. When the reaction is carried out in the presence of electron-rich arenes (anisole, phenol, indole derivatives), Friedel-Crafts addition may follow the cycloisomerization step. Only GaX3 salts proved able to catalyze these two C-C bond formation events. This specificity of gallium has been exploited for the synthesis of valuable polycyclic compounds that would be very difficult to prepare otherwise. For instance, tetrahydroisoquinolines and tetrahydrobenzoazepines have been obtained by selective 6-exo-dig or 7-endo-dig cyclization of N-tethered 1,6-arenynes. DFT calculations were carried out to shed light on the mechanism and provide a rationale for this regiodivergency. Computations also reveal the fundamental role of the tether in the stabilization of carbocationic species. Differential reactivities of other types of substrates in gallium- and gold-catalyzed cascades are also exposed, showing that the two approaches are complementary. In particular, bimolecular Friedel-Crafts additions are facilitated under gallium catalysis.
- Li, Hui-Jing,Guillot, Regis,Gandon, Vincent
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supporting information; experimental part
p. 8435 - 8449
(2011/03/19)
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- Borohydride exchange resin as an alternative method for deuterium labelling: selective reduction of aryl bromides
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Transition metal-activated borohydride exchange resin and borodeuteride exchange resin have been prepared and used for the selective reductive deuteration of aryl bromides. This methodology, which utilizes deuterated methanol as the primary source of labe
- Landvatter, Scott W.,Schauer, Douglas J.,Garnes, Keith T.,Mack, James F.,Killmer, Lewis B.
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p. 1025 - 1034
(2007/10/03)
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- Electroreductive Dehalogenation of Chlorinated Aromatic Ethers. Unexpected Electrogenerated Base Catalyzed Reactions
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The electroreductive dehalogenation of several mono- and polychlorinated aromatic ethers that serve as models of dioxins has been studied.The dechlorination was achieved by a simple constant-current electrolysis using a lead cathode in dimethylformamide.It was shown that 2,4,6-trichloroanisole undergoes successive dechlorination and the chlorine in the 2-position is selectively eliminated.Competitive reactions and cyclic voltammetric measurements suggested the increasing reactivity order of mono- di- trichloride for the reductive dechlorination.Use of allyl 2-chloro phenyl ether as a probe for radical cyclization indicated that free radical intermediates are of little importance.Thus, incipient radicals are immediately reduced to anionic intermediates.The electrolyses in the presence of deuterium oxide revealed proton sources for the present dechlorination.In these attempts, novel phenomena due to electrogenerated base (EGB) were found: di- and trichlorides underwent an unexpected overincorporation of deuterium in their dechlorinated products; a selective formation of Z-enol ethers from the allylic ethers was encountered.The mechanistic features of the present electroreductive dechlorination are discussed.
- Kimura, Makoto,Miyahara, Hiroyoshi,Moritani, Noriyuki,Sawaki, Yasuhiko
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p. 3897 - 3902
(2007/10/02)
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- Mechanism of Aromatic Hydroxylation in the Fenton and Related Reactions. One-Electron Oxidation and the NIH Shift
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Hydroxylation of substituted benzenes in the Fenton and peroxydisulfate oxidations has been studied mechanistically in relation to the NIH shift.One-electron oxidants such as Fe3+, Cu2+, and quinones increased the shift value effectively in aqueous or acetonitrile solutions.The shift values obtained were as high as 40 - 50 percent and dependent on both substituents (i. e., MeO Me, Cl, MeCO) and solvents.A high shift value was obtained also for the methoxylation, indicating unimportance of the arene oxide intermediate for the NIH shift.Oxygen reduced the shift effectively and sometimes was incorporated into product phenols with selective meta orientation.The means that oxygen abstracts a hydrogen atom from or adds to the oxycyclohexadienyl radical intermediate.It is concluded that the one-electron oxidation of the dienyl radical is the key step for the shift and its rates are dependent on substituents, oxidants, and solvents.
- Kurata, Tsunehiko,Watanabe, Yasumasa,Katoh, Makoto,Sawaki, Yasuhiko
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p. 7472 - 7478
(2007/10/02)
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- DEUTERIUM ISOTOPE EFFECTS IN THE META PHOTOCYCLOADDITION OF AROMATIC COMPOUNDS TO ALKENES
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Secondary deuterium isotope effects were observed in the meta photocycloaddition of several aromatic compounds to cyclopentene.
- de Vaal, P.,Lodder, G.,Cornelisse, J.
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p. 4395 - 4398
(2007/10/02)
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- Base-Catalyzed Fragmentation of 2,3-Dioxabicycloheptane, the Bicyclic Peroxide Nucleus of Prostaglandin Endoperoxides: Large Secondary Deuterium Kinetic Isotope Effects
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The influence of deuterium substitution on the rates of base-catalyzed rearrangements of 2,3-dioxabicycloheptane (1) is examined.The kinetic isotope effect observed previously with 1,4,5,6,7,7-hexadeuterio-1 (kH/kD = 7-8) is much larger than that observed with 1-deuterio-1 (kH/kD = 3-4) during fragmentation to levulinaldehyde.This reveals a large cumulative secondary deuterium isotope effect which accompanies rate-determining cleavage of the bridgehead C-H bond.Presumably cleavage of the C4-C7 bond also occurs during the rate-determining step and deuterium substitution on these carbons produces large secondary kinetic isotope effects.
- Zagorski, Michael G.,Salomon, Robert G.
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p. 1750 - 1759
(2007/10/02)
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- PHOTOCHEMICAL AROMATIC HYDROXYLATION BY AROMATIC AMINE N-OXIDES: REMARKABLE SOLVENT EFFECT ON NIH-SHIFT
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Photooxygenations of 4-(2)H-anisole (3) and o-xylene (5) by 3-methylpyridazine 2-oxide (1) or pyridine 1-oxide (2) were studied in a variety of solvents at varying irradiation temperatures.Remarkable solvent effect on NIH-shift coupled with their hydroxylation processes was observed.
- Ogawa, Yuji,Iwasaki, Shigeo,Okuda, Shigenobu
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p. 3637 - 3640
(2007/10/02)
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