- Formal Bromine Atom Transfer Radical Addition of Nonactivated Bromoalkanes Using Photoredox Gold Catalysis
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Organic transformations mediated by photoredox catalysis have been at the forefront of reaction discovery. Recently, it has been demonstrated that binuclear Au(I) bisphosphine complexes, such as [Au2(μ-dppm)2]X2, are capable of mediating electron transfer to nonactivated bromoalkanes for the generation of a variety of alkyl radicals. The transfer reactions of bromine, derived from nonactivated bromoalkanes, are largely unknown. Therefore, we propose that unique metal-based mechanistic pathways are at play, as this binuclear gold catalyst has been known to produce Au(III) Lewis acid intermediates. The scope and proposed mechanistic overview for the formal bromine atom transfer reaction of nonactivated bromoalkanes mediated by photoredox Au(I) catalysis is presented. The methodology presented afforded good yields and a broad scope which include examples using bromoalkanes and iodoarenes.
- Zidan, Montserrat,McCallum, Terry,Swann, Rowan,Barriault, Louis
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supporting information
p. 8401 - 8406
(2020/11/03)
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- Tandem Photoredox Catalysis: Enabling Carbonylative Amidation of Aryl and Alkylhalides
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We report a new visible-light-mediated carbonylative amidation of aryl, heteroaryl, and alkyl halides. A tandem catalytic cycle of [Ir(ppy)2(dtb-bpy)]+ generates a potent iridium photoreductant through a second catalytic cycle in the presence of DIPEA, which productively engages aryl bromides, iodides, and even chlorides as well as primary, secondary, and tertiary alkyl iodides. The versatile in situ generated catalyst is compatible with aliphatic and aromatic amines, shows high functional-group tolerance, and enables the late-stage amidation of complex natural products.
- Connell, Timothy U.,Forni, José A.,Micic, Nenad,Polyzos, Anastasios,Weragoda, Geethika
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supporting information
p. 18646 - 18654
(2020/08/21)
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- Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenes
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Starting from diverse alkene-tethered aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β-chiral amines with an enantioenriched aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.
- He, Jun,Xue, Yuhang,Han, Bo,Zhang, Chunzhu,Wang, You,Zhu, Shaolin
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supporting information
p. 2328 - 2332
(2020/01/08)
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- Nickel-catalyzed removal of alkene protecting group of phenols, alcohols via chain walking process
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An efficient nickel-catalyzed removal of alkene protection group under mild condition with high functional group tolerance through chain walking process has been established. Not only phenolic ethers, but also alcoholic ethers can be tolerated with the retention of stereocenter adjacent to hydroxyl group. The new reaction brings the homoallyl group into a start of new type of protecting group.
- Meng, Chenkai,Niu, Haolin,Ning, Juehan,Wu, Wengang,Yi, Jun
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supporting information
(2020/02/04)
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- Amidation of Aryl Chlorides Using a Microwave-Assisted, Copper-Catalyzed Concurrent Tandem Catalytic Methodology
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A concurrent tandem catalytic (CTC) methodology has been developed for the amidation of aryl chlorides where the aryl chloride is first converted to an aryl iodide via halogen exchange and the aryl iodide is subsequently transformed into the aryl amide. A variety of aryl chlorides were converted to aryl amides in up to 85% isolated yield using 20 mol % CuI, 60 mol % N,N′-cyclohexane-1,2-diamine, 2.2 equiv of K2CO3, and 1.05-1.5 equiv of amide in acetonitrile at 200 °C after 0.75-1 h. The same copper/ligand system served as multifunctional catalyst for both steps of the concurrent catalytic process with iodide present in substoichiometric amounts. Mechanistic studies were consistent with CTC amidation occurring via a nonradical mechanism. Kinetic modeling was conducted to investigate the effect of competitive direct amidation of an aryl chloride or aryl bromide on the formation of product over time during a CTC amidation reaction.
- Chang, Raymond K.,Clairmont, Brice P.,Lin, Shirley,MacArthur, Amy H. Roy
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supporting information
p. 4448 - 4454
(2019/11/13)
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- Neutral Organic Super Electron Donors Made Catalytic
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Neutral organic super electron donors (SEDs) display impressive reducing power but, until now, it has not been possible to use them catalytically in radical chain reactions. This is because, following electron transfer, these donors form persistent radical cations that trap substrate-derived radicals. This paper unlocks a conceptually new approach to super electron donors that overcomes this issue, leading to the first catalytic neutral organic super electron donor.
- Rohrbach, Simon,Shah, Rushabh S.,Tuttle, Tell,Murphy, John A.
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supporting information
p. 11454 - 11458
(2019/07/18)
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- CuI-Catalyzed Pentafluoroethylation of Aryl Iodides in the Presence of Tetrafluoroethylene and Cesium Fluoride: Determining the Route to the Key Pentafluoroethyl CuI Intermediate
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The Cu(I)-catalyzed pentafluoroethylation of iodoarenes via the fluorocupration of tetrafluoroethylene (TFE) is disclosed. The active species, (phen)CuC2F5, was isolated and its molecular structure confirmed by a single-crystal X-ray diffraction analysis. The key to the successful suppression of the competing oligomerization of TFE is to refrain from stirring the reaction mixture. A mechanistic study clearly discarded the possibility that the catalytic reaction proceeds via a radical pathway.
- Ohashi, Masato,Ishida, Naoyoshi,Ando, Kota,Hashimoto, Yu,Shigaki, Anna,Kikushima, Kotaro,Ogoshi, Sensuke
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supporting information
p. 9794 - 9798
(2018/07/25)
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- Cycloisomerization between Aryl Enol Ether and Silylalkynes under Ruthenium Hydride Catalysis: Synthesis of 2,3-Disubstituted Benzofurans
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Metal-catalyzed cycloisomerization reactions of 1,n-enynes have become conceptually and chemically attractive processes in the search for atom economy, which is a key subject of current research. However, metal-catalyzed cycloisomerization between aryl enol ether and silylalkynes has not been developed. The ruthenium hydride complex catalyzed cycloisomerization between aryl enol ether and silylalkynes is reported to give benzofurans having useful functional groups, vinyl and trimethylsilylmethyl, on the 2- and 3-positions, respectively.
- Ohno, Shohei,Takamoto, Kohei,Fujioka, Hiromichi,Arisawa, Mitsuhiro
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supporting information
p. 2422 - 2425
(2017/05/12)
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- Copper-catalysed aromatic-Finkelstein reactions with amine-based ligand systems
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A new efficient and low-cost ligand, diethylenetriamine, has been utilised to promote the iodination of 16 different bromo-substrates via the copper catalysed Finkelstein halogen exchange reaction under mild conditions. In contrast to earlier methods, the use of inert atmosphere conditions was not required to obtain high yields and purity. Studies on the speciation of the catalyst in solution indicate rapid disproportionation of copper(i) in the presence of diethylenetriamine to give copper(0) and a bis-ligated copper(ii) complex which is characterised by X-ray diffraction. This copper(ii) complex was also shown to be catalytically active in the halogen exchange reaction. In contrast, no significant disproportionation was observed using dimethylethylenediamine as the ligand, and the solid-state structures of a copper(i) dimeric complex and a 2D polymeric network of copper(i) iodide tetramers are reported. The catalytic activity of diethylenetriamine and dimethylethylenediamine with both copper(i) and copper(ii) salts are compared, and possible mechanistic implications discussed.
- Jin, Xiaodong,Davies, Robert P.
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p. 2110 - 2117
(2017/07/22)
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- Ligand-Free Heck Reactions of Aryl Iodides: Significant Acceleration of the Rate through Visible Light Irradiation at Ambient Temperature
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A mild Heck reaction of aryl iodides and olefins was realized by the cooperation of a palladium and a photoredox catalyst under the irradiation of visible light. This protocol works well to synthesize stilbenes with high Z/E ratios and (E)-cinnamates in the absence of ligands at ambient temperature. Control experiments revealed that palladium salt, visible light and photoredox catalyst were all crucial for the achievement of this cross-coupling under mild conditions. (Figure presented.).
- Zhang, Heng,Huang, Xueliang
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supporting information
p. 3736 - 3742
(2016/12/16)
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- Pushing the Limits of Neutral Organic Electron Donors: A Tetra(iminophosphorano)-Substituted Bispyridinylidene
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A new ground-state organic electron donor has been prepared that features four strongly π-donating iminophosphorano substituents on a bispyridinylidene skeleton. Cyclic voltammetry reveals a record redox potential of ?1.70 V vs. saturated calomel electrode (SCE) for the couple involving the neutral organic donor and its dication. This highly reducing organic compound can be isolated (44 %) or more conveniently generated in situ by a deprotonation reaction involving its readily prepared pyridinium ion precursor. This donor is able to reduce a variety of aryl halides, and, owing to its redox potential, was found to be the first organic donor to be effective in the thermally induced reductive S N bond cleavage of N,N-dialkylsulfonamides, and reductive hydrodecyanation of malonitriles.
- Hanson, Samuel S.,Doni, Eswararao,Traboulsee, Kyle T.,Coulthard, Graeme,Murphy, John A.,Dyker, C. Adam
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supporting information
p. 11236 - 11239
(2016/07/06)
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- Enantioselective Intramolecular C?H Insertion of Donor and Donor/Donor Carbenes by a Nondiazo Approach
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The first enantioselective intramolecular C?H insertion and cyclopropanation reactions of donor- and donor/donor-carbenes by a nondiazo approach are reported. The reactions were conducted in a one-pot manner without slow addition and provided the desired
- Zhu, Dong,Ma, Jun,Luo, Kui,Fu, Hongguang,Zhang, Li,Zhu, Shifa
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supporting information
p. 8452 - 8456
(2016/07/19)
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- Pd-Catalyzed Highly Regio- and Stereoselective Formation of C-C Double Bonds: An Efficient Method for the Synthesis of Benzofuran-, Dihydrobenzofuran-, and Indoline-Containing Alkenes
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A highly regio- and stereoselective C-C double bond formation reaction via Pd-catalyzed Heck-type cascade process with N-tosylhydrazones has been developed. Various N-tosylhydrazones derived from both ketones and aldehydes are found to be efficient substrates to provide di- and trisubstituted olefins with high regio- and stereoselectivity. Furthermore, this reaction has a good functional group tolerance and different benzofuran-, dihydrobenzofuran-, and indoline-containing alkene products were obtained with high selectivity.
- Gao, Yang,Xiong, Wenfang,Chen, Huoji,Wu, Wanqing,Peng, Jianwen,Gao, Yinglan,Jiang, Huanfeng
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p. 7456 - 7467
(2015/08/18)
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- Copper-catalyzed intermolecular C-H amination of (Hetero)arenes via transient unsymmetrical λ3-iodanes
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A one-pot two-step method for intermolecular C-H amination of electron-rich heteroarenes and arenes has been developed. The approach is based on a room-temperature copper-catalyzed regioselective reaction of the in situ formed unsymmetrical (hetero)aryl-λ3-iodanes with a wide range of primary and secondary aliphatic amines and anilines.
- Sokolovs, Igors,Lubriks, Dmitrijs,Suna, Edgars
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supporting information
p. 6920 - 6928
(2014/06/09)
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- Intramolecular carbonickelation of alkenes
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The efficiency of the intramolecular carbonickelation of substituted allylic ethers and amines has been studied to evaluate the influence of the groups borne by the double bond on this cyclization. The results show that when this reaction takes place, it affords only the 5-exo-trig cyclization products, viz. dihydrobenzofurans or indoles. Depending on the tethered heteroatom (O or N), the outcome of the cyclization differs. While allylic ethers are relatively poor substrates that undergo a side elimination and need an intracyclic double bond to proceed, allylic amines react well and afford indoline and indole derivatives. Finally, the synthesis of the trinuclear ACE core of a morphine-like skeleton was achieved by using NiBr2bipy catalysis.
- Lhermet, Rudy,Durandetti, Muriel,Maddaluno, Jacques
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supporting information
p. 710 - 716
(2013/06/05)
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- Highly diastereoselective radical cyclisations of chiral sulfinimines
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Chiral amines are formed by the highly diastereoselective intramolecular addition of alkyl and aryl radicals onto chiral mesityl sulfinimines.
- Rochette, Elise M.,Lewis, William,Dossetter, Al G.,Stockman, Robert A.
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supporting information
p. 9395 - 9397
(2013/10/01)
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- From ynamides to highly substituted benzo[b]furans: Gold(I)-catalyzed 5-endo-dig-cyclization/rearrangement of alkylic oxonium intermediates
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A series of arylynamides with alkyloxy groups at the ortho position of the aryl group was prepared through a short alkylation/cross-coupling/amidation sequence. The gold-catalyzed conversion of these substrates combined both C-O and C-C formation steps, thus providing benzofurans with amine functionalities at the 2-position and alkyl groups at the 3-position. Cross-over experiments showed that the alkyl-migration step was an intermolecular process. X-ray crystal-structure analysis of two of the products supported our structural assignment. In some cases, the corresponding benzofurans without the alkyl group at the 3-position were obtained as side-products, which were formed through a competing protodeauration process. Golden touch: Arylynamides with o-alkyloxy groups were prepared through an alkylation/cross-coupling/amidation sequence. Their Au-catalyzed conversion provided benzofurans with amine groups at the 2-position and alkyl groups at the 3-position. Copyright
- Blanco Jaimes, Maria Camila,Weingand, Vanessa,Rominger, Frank,Hashmi, A. Stephen K.
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supporting information
p. 12504 - 12511
(2013/09/23)
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- A novel organic electron donor derived from N-methylisatin
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We report the reactivity of an electron donor derived from N-methylisatin on reduction by sodium amalgam. Transfer of a clear supernatant solution to iodoarenes affords the products of two-electron reduction. Reductions of sulfones, activated arenesulfonamides, and Weinreb amides are also reported.
- Sword, Ryan,O'Sullivan, Steven,Murphy, John A.
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p. 314 - 322
(2013/05/08)
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- AMINO-5-[SUBSTITUTED-4-(DIFLUOROMETHOXY)PHENYL]-5- PHENYLIMIDAZOLONE COMPOUNDS AS ?-SECRETASE INHIBITORS
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The present invention provides a 2-amino-5-[substituted-4-(difluoromethoxy)phenyl]-5-phenylimidazolone compound of formula (I) The present invention also provides methods for the use thereof to inhibit ?-secretase (BACE) and treat ?-amyloid deposits and neurofibrillary tangles.
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-
Page/Page column 143-144
(2008/12/07)
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- Homolytic substitution at phosphorus for the synthesis of alkyl and aryl phosphanes
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(Chemical Equation Presented) A transition-metal-free radical phosphonation using Me3SnPPh2 and the less toxic Me 3SiPPh2 is reported. These readily available reagents react highly efficiently with primary and secondary alkyl radicals. Moreover, aryl radicals and tertiary alkyl radicals are phosphonated with Me 3SnPPh2 (see scheme; R = aryl, alkyl, vinyl; X = 1, Br, OC(S)imidazolyl). DFT calculations provide insights into the mechanism of the reaction.
- Vaillard, Santiago E.,Mueck-Lichtenfeld, Christian,Grimme, Stefan,Studer, Armido
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p. 6533 - 6536
(2008/09/17)
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- Tributylgermanium hydride as a replacement for tributyltin hydride in radical reactions
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Tributylgermanium hydride (Bu3GeH) can be used as an alternative to tributyltin hydride (Bu3SnH) as a radical generating reagent with a wide range of radical substrates. Tributylgermanium hydride has several practical advantages over tributyltin hydride, e.g. low toxicity, good stability and much easier work-up of reactions. The reagent can be easily prepared in good yield and stored indefinitely. Suitable substrates include iodides, bromides, activated chlorides, phenyl selenides, tert-nitroalkanes, thiocarbonylimidazolides and Barton esters. Alkyl, vinyl and aryl radicals can be generated in radical reactions including reduction and cyclisation processes. Common radical initiators such as ACCN and triethylborane can be used. The slower rate of hydrogen abstraction by carbon-centred radicals from Bu 3GeH as compared to Bu3SnH facilitates improved cyclisation yields. Polarity reversal catalysis (PRC) with phenylthiol can be used in reactions which generate stable radical intermediates which will not abstract hydrogen from Bu3GeH.
- Bowman, W. Russell,Krintel, Sussie L.,Schilling, Mark B.
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p. 585 - 592
(2007/10/03)
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- Regioselective synthesis of substituted 1-indanols, 2,3-dihydrobenzofurans and 2,3-dihydroindoles by electrochemical radical cyclization using an arene mediator
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Electrochemical reduction of haloarenes carrying 2-(1-hydroxybut-3-enyl), 2-allyloxy or N-allyl-N-methylamino group in the presence of phenanthrene as a mediator generated the corresponding aryl radicals and gave the corresponding 5-exo cyclization produc
- Kurono, Nobuhito,Honda, Eiichi,Komatsu, Fumikazu,Orito, Kazuhiko,Tokuda, Masao
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p. 1791 - 1801
(2007/10/03)
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- Diastereoselective intramolecular SmI2-H2O-amine mediated couplings
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The effectiveness of SmI2-H2O-amine mixture for intramolecular couplings was discussed. Diastereoselectivities in the coupling of O-cyclohexanyliodophenol derivatives were provided into heterocycles. The amount of coupled product improved significantly as SmI2, the substrate and amine were premixed followed by a gradual addition of water.
- Dahlen, Anders,Petersson, Annika,Hilmersson, Goeran
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p. 2423 - 2426
(2007/10/03)
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- Selectivity in the tandem cyclization - Carboxylation reaction of unsaturated haloaryl ethers catalyzed by electrogenerated nickel complexes
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The electrochemical reduction of a series of 2-haloaryl ethers containing allyl and propargyl groups under CO2 allows the synthesis of benzofuranacetic acid derivatives. This novel intramolecular cyclization- carboxylation reaction is carried out in single-compartment cells and is catalyzed by [Ni(cyclam)Br2].
- Olivero,Du?ach
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p. 1885 - 1891
(2007/10/03)
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- New formulas for organozincate chemistry
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As a new type of zincate, we designed various new organozinc derivatives, Me3Zn(R)Li2 (R = Me, CN, SCN), which could be prepared in situ from lithium trimethylzincate and anion species such as methyllithium, lithium cyanide, and lithium thiocyanate. We investigated the reactivities of these zincates toward the halogen (or tellurium)-zinc exchange, Michael addition, carbozincation, and epoxide ring opening reactions. On the basis of their excellent chemical yields and chemoselectivities, these species were considered to be differentiated from ordinary triorganozincates, R3ZnLi. We also discuss the structure of the newly designed zincates using 1H NMR/Raman/in situ FTIR/extended X-ray absorption the structure (EXAFS) spectroscopic and the density functional theory (DFT) theoretical studies. All results strongly support the fact that these newly designed zincates are a new category of zincate species. This observation is also identical with the fact that newly designed zincates have a higher and unique reactivity compared to the conventional triorganozincates.
- Uchiyama, Masanobu,Kameda, Mitsuyoshi,Mishima, Osamu,Yokoyama, Nobuko,Koike, Minako,Kondo, Yoshinori,Sakamoto, Takao
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p. 4934 - 4946
(2007/10/03)
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- Mechanism of Arylation of Nucleophiles by Aryllead Triacetates. Part 1. Exclusion of a Pathway involving Aryl Free Radicals
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o-(Prop-2-enyloxy)phenyllead triacetate 6, which was obtained by treatment of the corresponding boronic acid with lead tetraacetate, has been shown to react with iodide and azide ions, 2,4,6-trimethylphenol, ethyl 2-oxocyclopentanecarboxylate, and the sodium salt of 2-nitropropane to give only those products which, in a formal sense, are derived by direct nucleophilic displacement of the Pb(OAc)3 group.The complete absence of 3-substituted dihydrobenzofurans among the products is strong evidence that aryl free radicals are not involved in the arylation reactions of aryllead triacetates.
- Morgan, Jacqueline,Pinhey, John T.
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p. 1673 - 1676
(2007/10/02)
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- The samarium grignard reaction. In situ formation and reactions of primary and secondary alkylsamarium(III) reagents
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This work shows that primary and secondary radicals are rapidly reduced in THF/HMPA to form primary- and secondary-alkylsamarium reagents. The primary- and secondary-radicals can be formed either by direct SmI2 reduction of primary- and secondary-halides or by a previous rapid radical cyclization. The samarium reagents have moderate stability in solution, and they react with a variety of typical electrophiles, including aldehydes and ketones. The work further shows that organosamarium intermediates can be involved in the traditional samarium Barbier reaction of aldehydes and ketones conducted in THF/HMPA. A new procedure called the "samarium Grignard" method is introduced, and it is suggested that this new procedure will have considerably more scope and generality than the samarium Barbier reaction.
- Curran, Dennis P.,Totleben, Michael J.
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p. 6050 - 6058
(2007/10/02)
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- Induction of radical cyclizations with the 10-methyl-9,10-dihydroacridine / NaBH4 photocatalytic system
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The radical cyclization of suitably unsaturated aromatic halides, such as 1-allyloxy-2-halobenzenes (1a-d), can be induced with the 10-methyl-9,10-dihydroacridine / NaBH4 photocatalytic system in DMF. The method is preparatively useful with the most reactive halides.
- Boisvert, Guy,Giasson, Richard
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p. 6587 - 6590
(2007/10/02)
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- Efficient Free-Radical and Palladium-Catalyzed Tandem Alkene Insertions: A New Approach to Benzoprostacyclins
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Several stereoisomeric benzoprostacyclins are readily available from a common intermediate (11) via free-radical and palladium-promoted tandem alkene insertion processes.
- Larock, Richard C.,Lee, Nam Ho
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p. 6253 - 6254
(2007/10/02)
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- Reductive Radical Cyclizations of Haloalkenes Promoted by Samarium Diiodide. Sequential Cyclization/Intermolecular Carbonyl Addition Reactions
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A sequential radical cyclization/intermolecular carbonyl addition process promoted by samarium(II) iodide (SmI2) is reported.Treatment of appropriate haloalkenes with SmI2 in the presence of a variety of ketones leads to products resulting from cyclization followed by intermolecular addition of the resultant anion to the carbonyl electrophiles.Although several mechanisms can be envisioned, this process is most likely initiated by SmI2-induced formation of a hexenyl radical.Intramolecular addition of this radical to the tethered alkene leads to generation of a new alkyl radical, which can be reduced in situ to the corresponding organosamarium species.This organosamarium adds to the carbonyl electrophile, completing the tandem process.In this study, 2-(allyloxy)ethyl iodide and 2-(allyloxy)-1-iodobenzene were the most thoroughly examined radical precursors.The anion intermediates ultimately derived from these starting materials were trapped with a range of ketones to yield the corresponding heterocyclic derivatives.
- Molander, Gary A.,Harring, Lori S.
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p. 6171 - 6176
(2007/10/02)
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- THE REACTIONS OF ALLYL o-BROMOARYL ETHERS, N-ALLYL o-BROMOACETANILIDE, AND RELATED COMPOUNDS WITH TRIBUTYLTIN HYDRIDE IN THE PRESENCE OF ACTIVATED OLEFINS
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o-Bromophenyl allyl ether, N-allyl o-bromoacetanilide, and related compounds reacted with tributyltin hydride in the presence of activated olefins to give 2,3-dihydrobenzofuran, 2,3-dihydroindole, and analogous derivatives in modest yields respectively vi
- Togo, Hideo,Kikuchi, Osamu
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p. 373 - 381
(2007/10/02)
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