- Ultrasound assisted nitratobis(triphenyl phosphine) copper(I) catalyzed conjugate addition of alkyl or aryl bromides to α,β-unsaturated cyanoester
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The α,β-unsaturated cyanoester was obtained from p-methoxy benzaldehyde and ethyl cyano acetate by reported method. The conjugated addition products were synthesized from alkyl or aryl bromides and α,β-unsaturated cyanoester in the presence of 10 mol % Cu(I) catalyst in high yields within 17-21 min under ultrasound irradiation.
- Pise, Ashok S.,Burungale, Arvind S.,Devkate, Santosh S.,Gawade, Ramesh B.,Jadhav, Sunil D.
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- Role of Electron-Deficient Olefin Ligands in a Ni-Catalyzed Aziridine Cross-Coupling to Generate Quaternary Carbons
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We previously reported the development of an electron-deficient olefin (EDO) ligand, Fro-DO, that promotes the generation of quaternary carbon centers via Ni-catalyzed Csp3-Csp3 cross-coupling with aziridines. By contrast, electronically and structurally similar EDO ligands such as dimethyl fumarate and electron-deficient styrenes afford primarily β-hydride elimination side reactivity. Only a few catalyst systems have been identified that promote the formation of quaternary carbons via Ni-catalyzed Csp3-Csp3 cross-coupling. Although Fro-DO represents a promising ligand in this regard, the basis for its superior performance is not well understood. Here we describe a detailed mechanistic study of the aziridine cross-coupling reaction and the role of EDO ligands in facilitating Csp3-Csp3 bond formation. This analysis reveals that cross-coupling proceeds by a Ni0/II cycle with a NiII azametallacyclobutane catalyst resting state. Turnover-limiting C-C reductive elimination occurs from a spectroscopically observable NiII-dialkyl intermediate bound to the EDO. Computational analysis shows that Fro-DO accelerates turnover limiting reductive elimination via LUMO lowering. However, it is no more effective than dimethyl fumarate at reducing the barrier to Csp3-Csp3 reductive elimination. Instead, Fro-DO's unique reactivity arises from its ability to associate favorably to NiII intermediates. Natural bond order second-order perturbation theory analysis of the catalytically relevant NiII intermediate indicates that Fro-DO binds to NiII through an additional stabilizing donor-acceptor interaction between its sulfonyl group and NiII. Design of new ligands to evaluate this proposal supports this model and has led to the development of a new and tunable ligand framework.
- Estrada, Jesús G.,Williams, Wendy L.,Ting, Stephen I.,Doyle, Abigail G.
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supporting information
p. 8928 - 8937
(2020/05/13)
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- Fukuyama Cross-Coupling Approach to Isoprekinamycin: Discovery of the Highly Active and Bench-Stable Palladium Precatalyst POxAP
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An efficient and user-friendly palladium(II) precatalyst, POxAP (post-oxidative-addition precatalyst), was identified for use in Fukuyama cross-coupling reactions. Suitable for storage under air, the POxAP precatalyst allowed reaction between thioesters and organozinc reagents with turnover numbers of ～90000. A series of 23 ketones were obtained with yields ranging from 53 to 99%. As proof of efficacy, an alternative approach was developed for the synthesis of a key precursor of the natural product isoprekinamycin.
- Tang, Shuang-Qi,Bricard, Jacques,Schmitt, Martine,Bihel, Frédéric
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supporting information
p. 844 - 848
(2019/01/30)
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- Palladium(II)/Copper(II)-Catalyzed C–H Sulfidation or Selenation of Arenes Leading to Unsymmetrical Sulfides and Selenides
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A novel palladium(II)/copper(II)-catalyzed sulfidation of the C–H bond in electron-rich arenes and in pentafluorobenzene with disulfides was developed. This catalytic system can be used to efficiently produce various types of either unsymmetrical aryl sulfides or alkyl aryl sulfides. The present protocol could also be applied to the direct preparation of unsymmetrical aryl selenides via C–H selenation.
- Nishino, Kota,Tsukahara, Shouya,Ogiwara, Yohei,Sakai, Norio
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supporting information
p. 1588 - 1593
(2019/02/09)
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- Mechanochemical Activation of Zinc and Application to Negishi Cross-Coupling
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A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross-coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp3)–C(sp2) and C(sp2)–C(sp2) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.
- Cao, Qun,Howard, Joseph L.,Wheatley, Emilie,Browne, Duncan L.
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supporting information
p. 11339 - 11343
(2018/08/28)
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- Generation and Cross-Coupling of Organozinc Reagents in Flow
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A versatile flow synthesis method for in situ formation of organozinc reagents and subsequent cross-coupling with aryl halides and activated carboxylic acids is reported. Formation of organozinc reagents is achieved by pumping organic halides, in the presence of ZnCl2 and LiCl, through an activated Mg-packed column under flow conditions. This method provides efficient in situ formation of aryl, primary, secondary, and tertiary alkyl organozinc reagents, which are subsequently telescoped downstream to a Negishi or decarboxylative Negishi cross-coupling reaction. The described method offers access to a variety of C-C bond formations with organozinc reagents that are otherwise commercially unavailable or difficult to prepare under traditional batch reaction conditions.
- Herath, Ananda,Molteni, Valentina,Pan, Shifeng,Loren, Jon
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supporting information
p. 7429 - 7432
(2019/01/03)
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- Exploiting Synergistic Effects in Organozinc Chemistry for Direct Stereoselective C-Glycosylation Reactions at Room Temperature
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Pairing a range of bis(aryl) zinc reagents ZnAr2 with the stronger Lewis acidic [(ZnArF2)] (ArF=C6F5), enables highly stereoselective cross-coupling between glycosyl bromides and ZnAr2 without the use of a transition metal. Reactions occur at room temperature with excellent levels of stereoselectivity, where ZnArF2 acts as a non-coupling partner although its presence is crucial for the execution of the C(sp2)–C(sp3) bond formation process. Mechanistic studies have uncovered a unique synergistic partnership between the two zinc reagents, which circumvents the need for transition-metal catalysis or forcing reaction conditions. Key to the success of the coupling is the avoidance of solvents that act as Lewis bases versus diarylzinc compounds (e.g. THF).
- Hernán-Gómez, Alberto,Orr, Samantha A.,Uzelac, Marina,Kennedy, Alan R.,Barroso, Santiago,Jusseau, Xavier,Lemaire, Sébastien,Farina, Vittorio,Hevia, Eva
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supporting information
p. 10630 - 10634
(2018/08/01)
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- Cobalt-Catalyzed Oxidative Homocoupling of Arylzinc Species
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A novel procedure for the synthesis of functionalized symmetrical biaryl compounds is described. The reaction proceeds via the oxidative homocoupling of arylzinc species formed by cobalt catalysis in the presence of air or p-benzoquinone depending on the nature of the functional group.
- Bourne-Branchu, Yann,Moncomble, Aurélien,Corpet, Martin,Danoun, Gregory,Gosmini, Corinne
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p. 3352 - 3356
(2016/09/12)
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- α-C-Glycosides via syn Opening of 1,2-Anhydro Sugars with Organozinc Compounds in Toluene/n-Dibutyl Ether
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The diastereoselective addition of organozinc species to 1,2-anhydro sugars in toluene/n-dibutyl ether solvent is reported. Compared to the existing methods, the reaction proceeds at 0 °C, and only a slight excess of nucleophile is required to achieve good yields. Scope was assessed with different O-protected glycals along with various nucleophiles (aryl, alkynyl). This methodology was applied to the synthesis of the α-anomer of canagliflozin.
- Wagschal, Simon,Guilbaud, Johan,Rabet, Pauline,Farina, Vittorio,Lemaire, Sébastien
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p. 9328 - 9335
(2015/09/28)
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- Electron-deficient olefin ligands enable generation of quaternary carbons by Ni-catalyzed cross-coupling
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A Ni-catalyzed Negishi cross-coupling with 1,1-disubstituted styrenyl aziridines has been developed. This method delivers valuable β-substituted phenethylamines via a challenging reductive elimination that affords a quaternary carbon. A novel electron-deficient olefin ligand, Fro-DO, proved crucial for achieving high rates and chemoselectivity for C-C bond formation over β-H elimination. This ligand is easy to access, is stable, and presents a modular framework for reaction discovery and optimization. We expect that these attributes, combined with the fact that the ligands impart distinct electronic properties to a metal, will support the invention of new transformations not previously possible using established ligands.
- Huang, Chung-Yang,Doyle, Abigail G.
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supporting information
p. 5638 - 5641
(2015/05/20)
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- On the remarkably different role of salt in the cross-coupling of arylzincs from that seen with alkylzincs
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The role of halide salt additives has been investigated in the Negishi reaction involving aryl zinc reagents. Diarylzincs readily transmetallate to Pd in relatively non-polar media (e.g., THF) with zero salt present and coupling proceeds. Arylzinc halides
- McCann, Lucas C.,Organ, Michael G.
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supporting information
p. 4386 - 4389
(2014/05/06)
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- Negishi cross-coupling reaction as a simple and efficient route to functionalized amino and alkoxy carbene complexes of chromium, molybdenum, and Tungsten
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Synthesis of functionalized phenyl, 2-thienyl, and N-methyl-pyrrol-2-yl Fischer carbene complexes of chromium and tungsten was achieved via a Negishi cross-coupling reaction of metalated aminocarbenes in the presence of a palladium catalyst. The reverse a
- Tobrman, Tom,Jurskov, Ivana,Dvok, Dalimil
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p. 6593 - 6603
(2015/02/19)
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- Cobalt-catalyzed electrophilic amination of arylzincs with N-chloroamines
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Roles reversed: An efficient cobalt-catalyzed electrophilic amination of arylzinc reagents has been achieved. A variety of functionalized arylzincs and N-chloroamines were coupled under mild conditions (see scheme). Both secondary and tertiary arylamines were obtained in moderate to excellent yields. Copyright
- Qian, Xin,Yu, Zailu,Auffrant, Audrey,Gosmini, Corinne
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supporting information
p. 6225 - 6229
(2013/07/05)
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- Nickel-catalyzed enantioselective arylation of pyridinium ions: Harnessing an iminium ion activation mode
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A nickel for your thoughts.?? An enantioselective nickel-catalyzed cross-coupling between N-acylpyridinium salts and organozinc reagents is reported. The catalytic system, which is comprised of an air-stable NiII source and a chiral phosphoramidite ligand, affords 2-substituted-2,3-dihydro-4-pyridones with up to >99 % ee. Copyright
- Chau, Stephen T.,Lutz, J. Patrick,Wu, Kevin,Doyle, Abigail G.
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supporting information
p. 9153 - 9156
(2013/09/12)
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- Directed nickel-catalyzed negishi cross coupling of alkyl aziridines
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Herein we report a nickel-catalyzed C-C bond-forming reaction between simple alkyl aziridines and organozinc reagents. This method represents the first catalytic cross-coupling reaction employing a nonallylic and nonbenzylic Csp3-N bond as an electrophile. Key to its success is the use of a new N-protecting group (cinsyl or Cn) bearing an electron-deficient olefin that directs oxidative addition and facilitates reductive elimination. Studies pertinent to elucidation of the mechanism of cross coupling are also presented.
- Nielsen, Daniel K.,Huang, Chung-Yang,Doyle, Abigail G.
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supporting information
p. 13605 - 13609
(2013/09/24)
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- Cobalt-catalyzed addition of arylzinc reagents to alkynes to form ortho-alkenylarylzinc species through 1,4-cobalt migration
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Migratory carbometalation: A cobalt-Xantphos complex catalyzes the addition of an arylzinc reagent to an unactivated internal alkyne; the reaction most likely involves insertion of the alkyne into an arylcobalt species and vinyl-to-aryl 1,4-cobalt migration, followed by transmetalation with the arylzinc reagent. Interception of the resulting ortho-alkenylarylzinc species with electrophiles allows access to 1-alkenyl arenes functionalized in the 2-position. Copyright
- Tan, Boon-Hong,Dong, Jinghua,Yoshikai, Naohiko
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supporting information
p. 9610 - 9614
(2012/11/07)
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- Replacing conventional carbon nucleophiles with electrophiles: Nickel-catalyzed reductive alkylation of aryl bromides and chlorides
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A general method is presented for the synthesis of alkylated arenes by the chemoselective combination of two electrophilic carbons. Under the optimized conditions, a variety of aryl and vinyl bromides are reductively coupled with alkyl bromides in high yields. Under similar conditions, activated aryl chlorides can also be coupled with bromoalkanes. The protocols are highly functional-group tolerant (-OH, -NHTs, -OAc, -OTs, -OTf, -COMe, -NHBoc, -NHCbz, -CN, -SO2Me), and the reactions are assembled on the benchtop with no special precautions to exclude air or moisture. The reaction displays different chemoselectivity than conventional cross-coupling reactions, such as the Suzuki-Miyaura, Stille, and Hiyama-Denmark reactions. Substrates bearing both an electrophilic and nucleophilic carbon result in selective coupling at the electrophilic carbon (R-X) and no reaction at the nucleophilic carbon (R-[M]) for organoboron (-Bpin), organotin (-SnMe3), and organosilicon (-SiMe2OH) containing organic halides (X-R-[M]). A Hammett study showed a linear correlation of σ and σ(-) parameters with the relative rate of reaction of substituted aryl bromides with bromoalkanes. The small ρ values for these correlations (1.2-1.7) indicate that oxidative addition of the bromoarene is not the turnover-frequency determining step. The rate of reaction has a positive dependence on the concentration of alkyl bromide and catalyst, no dependence upon the amount of zinc (reducing agent), and an inverse dependence upon aryl halide concentration. These results and studies with an organic reductant (TDAE) argue against the intermediacy of organozinc reagents.
- Everson, Daniel A.,Jones, Brittany A.,Weix, Daniel J.
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p. 6146 - 6159
(2012/05/07)
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- Cobalt-catalysed synthesis of highly substituted styrene derivatives via arylzincation of alkynes
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A new two-step procedure was developed by carbozincation of internal and terminal alkynes to synthesise highly functionalised vinylzinc bromides. Various tri and tetrasubstituted alkenes were prepared in moderate to good yields under mild reaction conditions in a stereo-selective manner. This methodology represents an interesting alternative to previously known methods. This journal is
- Corpet, Martin,Gosmini, Corinne
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supporting information
p. 11561 - 11563,3
(2012/12/12)
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- Lithium organozincate complexes LiRZnX2: Common species in organozinc chemistry
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We have used a combination of electrospray ionization (ESI) mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to investigate the effect of LiCl on solutions of organylzinc halides RZnX (R = Bu, Bn, Ph; X = halogen) and dibutylzinc Bu2Zn in tetrahydrofuran. In the case of RZnX, the addition of LiX (X = Cl) leads to a steep rise of the ESI signal intensities of RZnX2- organozincate anions. At the same time, the electrical conductivities strongly increase and the NMR absorptions of the α-H atoms of BuZnX shift upfield. These results consistently point to the formation of lithium organozincates Li +RZnX2-. As the most common syntheses of RZnX reagents involve stoichiometric amounts of LiX salts, Li+RZnX 2- complexes are supposedly widespread and may hold the key to understanding the marked effects of LiCl on the reactivity of organozinc halides. In contrast, we find Bu2Zn to have a much lower tendency to add LiCl and form ate complexes. This result is in line with the weak effect of LiCl on the reactivity of diorganozinc compounds reported in the literature.
- Fleckenstein, Julia E.,Koszinowski, Konrad
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p. 5018 - 5026
(2011/11/07)
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- Copper-Catalyzed Electrophilic Amination of Diorganozinc Reagents
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The copper-catalyzed electrophilic amination of diorganozinc reagents employing O-acyl N,N-dialkyl hydroxylamine derivatives as aminating agents is described. This reaction offers a general method for the preparation of tertiary amines in high yields and is noteworthy for its convenience both in terms of reaction conditions employed (room temperature, ≤1 h) and ease of product isolation (acid/base extractive workup). Copyright
- Berman, Ashley M.,Johnson, Jeffrey S.
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p. 5680 - 5681
(2007/10/03)
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- Preparation of aromatic organozinc compounds and composition therefor
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The invention relates to a technique for preparing aromatic organozinc compounds and to a composition therefore. This composition constitutes a reactant that can be used to carry out the synthesis of organozinc compounds, and comprises a cobalt salt, a zinc salt, a polar aprotic solvent and elemental zinc in divided form, the elemental zinc being in solid form, the other elements being in a form dissolved in the solvent. Application to organic synthesis.
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- New chemical synthesis of functionalized arylzinc compounds from aromatic or thienyl bromides under mild conditions using a simple cobalt catalyst and zinc dust
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A new chemical method for the preparation of arylzinc intermediates is described in acetonitrile, on the basis of the activation of aryl bromides by low-valent cobalt species arising from the reduction of cobalt halide by zinc dust. This procedure allows for the synthesis of a variety of functionalized aryl- and thienylzinc species in good to excellent yields. The versatility and the simplicity of that original method represent an alternative to most known procedures.
- Fillon, Hyacinthe,Gosmini, Corinne,Perichon, Jacques
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p. 3867 - 3870
(2007/10/03)
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