- Two palladium-catalyzed domino reactions from one set of substrates/reagents: Efficient synthesis of substituted indenes and cis-stilbenoid hydrocarbons from the same internal alkynes and hindered Grignard reagents
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(Chemical Equation Presented) Two types of domino reactions from the same internal alkynes and hindered Grignard reagents based on carbopalladation, Pd-catalyzed cross-coupling reaction, and a C-H activation strategy are described. The realization of thes
- Dong, Cheng-Guo,Yeung, Pik,Hu, Qiao-Sheng
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Read Online
- A "Classical" Tetrahydroxycalix[4]arene Adopting the 1,2-Alternate Conformation
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The first example of a "classical" tetrahydroxycalixarene, which adopts the 1,2-alternate conformation both in solution and in the crystal, is described. Calixarene derivatives with two distal methylene groups substituted in a trans fashion by phenyl (5a)
- Simaan, Samah,Biali, Silvio E.
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Read Online
- Strategy for Selective Csp2-F and Csp2-Csp2Formations from Organoplatinum Complexes
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By changing the parameters of fluorination reaction of bisaryl-platinum(II) complexes, each possible competitive pathway of Ar-Ar and Ar-F formation can be selectively controlled. It was discovered that steric hindrance, type of fluorinating reagent, and
- Sarkissian, Elin,Golbon Haghighi, Mohsen
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supporting information
p. 1016 - 1020
(2021/02/05)
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- A practical procedure for iron-catalyzed cross-coupling reactions of sterically hindered aryl-grignard reagents with primary alkyl halides
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Although iron-catalyzed cross-coupling reactions of arylmagnesium halides with alkyl halides are well established and proceed effectively under a variety of experimental conditions, they often find limitations when working with sterically hindered aryl-Grignard reagents. Outlined in this paper is a practical solution that allows this gap in coverage to be filled. Specifically, it is shown that bis(diethylphosphino)ethane (depe) crafts an effective coordination environment about Fe(+2). This commercially available ligand is slim enough not to interfere with the loading of the iron center even by ortho,ortho-disubstituted arylmagnesium halides, yet capable of preventing premature reductive coupling of the resulting organoiron species, which seem to be hardly basic either. The reaction is compatible with various polar functional groups as well as with substrates containing β-heteroatom substituents. Moreover, the procedure even allows encumbered neopentylic electrophiles to be arylated with donors as bulky as mesitylmagnesium bromide, whereas secondary alkyl halides tend to eliminate.
- Sun, Chang-Liang,Krause, Helga,Fuerstner, Alois
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p. 1281 - 1291
(2014/05/06)
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- Iron-catalyzed quick homocoupling reaction of aryl or alkynyl Grignard reagents using a phosphonium ionic liquid solvent system
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The iron-catalyzed homocoupling reaction of aryl Grignard reagent was completed very quickly when the reaction was carried out in a phosphonium salt ionic liquid solvent system at 0°C for 5 min. Using a similar reaction system, the first example of the iron-catalyzed homocoupling reaction of alkynyl Grignard reagents has also been accomplished using the ionic liquid technology.
- Kude, Keisuke,Hayase, Shuichi,Kawatsura, Motoi,Itoh, Toshiyuki
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experimental part
p. 397 - 404
(2012/01/13)
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- Structure-activity relationship analysis of Pd-PEPPSI complexes in cross-couplings: A close inspection of the catalytic cycle and the precatalyst activation model
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A series of Pd-N-heterocyclic carbene (Pd-NHC) complexes with various NHC, halide and pyridine ligands (PEPPSI (pyridine, enhanced, precatalyst, preparation, stabilisation and initiation) precatalysts) were prepared, and the effects of these ligands on catalyst activation and performance were studied in the Kumada-TamaoCorriu (KTC), Negishi, and Suzuki-Miyaura cross-coupling reactions. The lowered reactivity of more hindered 2,6-dimethylpyridyl complex 4 in the Negishi and KTC reactions is consistent with slow reductive dimerisation of the organometallic reaction partner during precatalyst activation. Comparative rate studies of complexes 1, 4 and 5 in the KTC and Suzuki-Miyaura reactions verify that 4 activated more slowly than the others. A potential on/ off mechanism of pyridine coordination to NHC-Pd0 is also plausible, in which the more basic pyridine stays bound for longer.
- Nasielski, Joanna,Hadei, Nilofaur,Achonduh, George,Kantchev, Eric Assen B.,O'Brien, Christopher J.,Lough, Alan,Organ, Michael G.
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supporting information; scheme or table
p. 10844 - 10853
(2010/12/19)
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- Synthesis of coordinatively unsaturated mesityliron thiolate complexes and their reactions with elemental sulfur
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The reactions of Fe2Mes4 (1; Mes = mesityl) with bulky thiols, namely, HSDmp (Dmp = 2,6-dimesitylphenyl), HSDxp (Dxp = 2,6-dixylylphenyl), and HSBtip [Btip = 2,6-(2,4,6-iPr 3C6H2)2C6H3], provided a series of iron(II) mesityl complexes bearing bulky thiolate ligands. These iron complexes are the thiolate-bridged dinuclear complexes Fe 2Mes2(μ-SAr)(μ-Mes) (2a, Ar = Dmp; 2b, Ar = Dxp), the 1,2-dimethoxyethane (DME) adducts (DME)Fe(SAr)(Mes) (3a, Ar = Dmp; 3b, Ar = Dxp), the mixed-valence FeI?FeII dinuclear complexes (Mes)Fe(μ-SAr)(μ-SAr)Fe (4a, Ar = Dmp; 4b, Ar = Dxp), and a low-coordinate mononuclear complex (BtipS)Fe(Mes) (5). An [Fe8S7] cluster [Fe4S3(SDmp)]2(μ-SDmp) 2(μ-SMes)(μ6-S) (6), the core structure of which is topologically relevant to that of the FeMo-cofactor of nitrogenase, was obtained from the reaction of 3a or 4a with S8. The μ-SMes ligand in 6 is formed via insertion of a sulfur atom into the Fe?C(Mes) bond. The formation of cluster 6 from 3a or 4a demonstrates that organoiron complexes are applicable as precursors for iron?sulfur clusters.
- Hashimoto, Takayoshi,Ohki, Yasuhiro,Tatsumi, Kazuyuki
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experimental part
p. 6102 - 6109
(2010/08/21)
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- Pd-PEPPSI-IPent: Low-temperature negishi cross-coupling for the preparation of highly functionalized, tetra-ortho-substituted biaryls
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(Chemical Equation Presented) Cool couplings: Complex, hindered biaryls have been prepared at temperatures ranging from 0°C to room temperature, or with gentle heating. The Pd-PEPPSI-IPent catalyst (see scheme) nicely couples starting materials containing acidic moieties and routinely prepares biaryl derivatives where one or both rings comprising the biaryl are heterocyclic. Ar1=hindered aryl or heteroaryl, Ar2=unactivated aryl or heteroaryl.
- Calimsiz, Selcuk,Sayah, Mahmoud,Mallik, Debasis,Organ, Michael G.
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supporting information; scheme or table
p. 2014 - 2017
(2010/06/20)
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- Grignard reagents in ionic solvents: Electron transfer reactions and evidence for facile Br-Mg exchange
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Grignard reagents form persistent solutions in phosphonium ionic liquids possessing O-donor anions and these solutions are excellent reaction media for electron transfer processes and transmetallation reactions. The Royal Society of Chemistry.
- Ramnial, Taramatee,Taylor, Stephanie A.,Clyburne, Jason A. C.,Walsby, Charles J.
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p. 2066 - 2068
(2008/02/08)
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- Optical Rotation of Quaterphenyl Derivatives
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Quatermesityl (2) has been resolved by chromatography into pure enantiomers; (S)-(+)-2 shows D = +108 as expected. (S)-(+)-3,3'-Diphenylbimesityl (9) has been prepared enantiospecifically and shows D = +106.Chromatographic reso
- Fischer, Erika,Hess, Heinrich,Lorenz, Thomas,Musso, Hans,Rossnagel, Ingrid
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p. 783 - 789
(2007/10/02)
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- Reactivity of carbon monoxide towards high valent molybdenum complexes
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Reaction of carbon monoxide (3 atm) with Mo(O)2(mes)2 (mes = mesityl = C6H2Me3-2,4,6) in pyridine at room temperature affords dimesityl ketone 1 (5percent) and 1,1'-bis(mesitoyl)-1,1',4,4'-tetrahydro-4,4'-bipyridine 2 (25percent), the molecular structure of which has been determined by an X-ray diffraction study.The formation of 2 represents the first example of N-acylation of a pyridine by CO mediated by a transition metal complex.It has been shown that the relative ratio of 1 and 2 is dependent on the reaction conditions and that the presence of pyridine is essential for the formation of 1.Reactions of CO with the isoelectronic complex Mo(NtBu)2mes2 contrast sharply with Mo(O)2mes2 and, under the same conditions, no dihydropyridine is formed, the sole identified products being 1 (60percent) and mesityltertiobutyl amide HN(1Bu)COmes (40percent).In light of the experimental results and of extended Hueckel calculations on dioxo and diimido d0 molybdenum complexes, a tentative mechanism for the formation of 2 is proposed which involves oxycarbene-like intermediates in the case of the more electrophilic dioxo molybdenum species.
- Lai, Richard,Bot, Sylvie Le,Djafri, Fatiha
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p. 335 - 345
(2007/10/02)
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- Trimesitylgermyllithium: synthese et reactivite
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The new organogermyllithium Mes3GeLi has been prepared in good yield by hydrogermolysis reaction of t-butyllithium in THF.The bulky group favours stabilization in the form of the THF complex.Mes3GeLi has been characterized by alkylation reaction with MeI.
- Castel, A.,Riviere, P.,Satge, J.,Ko, Y.H.,Desor, D.
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- Thallium in Organic Synthesis. 58. Regiospecific Intermolecular Oxidative Dehydrodimerization of Aromatic Compounds to Biaryls Using Thallium (III) Trifluoroacetate
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Treatment of a variety of aromatic substrates with thallium(III) trifluoroacetate (TTFA) in trifluoroacetic acid (TFA), or in carbon tetrachloride or acetonitrile containing boron trifluoride etherate, results in smooth, rapid, and direct regiospecific oxidative dehydrodimerization to give symmetrical biaryls in good to excellent yield.The method is particularly useful when applied to substrates in which the ring substituents are either electron donating or mildly electron withdrawing.Aromatic substrates which contain powerful electron-withdrawing groups (CN, COOR, NO2) fail to react.The reaction is postulated to proceed via (a) reaction of TTFA with the aromatic substrate and generation of the radical cation Ar+; (b) reaction of this electrophile with the aromatic substrate; (c) oxidative aromatization of the intermediate thus produced by TTFA.Biaryls can be obtained similarly by oxidation of the same substrates with either mercury(II) trifluoroacetate in TFA containing boron trifluoride, lead(IV) acetate in acetonitrile containing boron trifluoride, iron(III) chloride in methylene chloride, or cobalt(III) fluoride in TFA.Yields in the Hg(II) and Fe(III) reactions are generally inferior to those obtained with TTFA, but those obtained in the Pb(IV) and Co(III) oxidations are in many instances comparable to, or even better than, the TTFA results.The oxidations with Hg(II), Pb(IV), Fe(III), and CO(III) are also postulated to proceed via a radical cation mechanism.
- McKillop, Alexander,Turrell, Andrew G.,Young, Derek W.,Taylor, Edward C.
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p. 6504 - 6512
(2007/10/02)
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- Electron-transfer Chain Catalysis of Substitution Reactions. Experimental Evidence for the SON2 Mechanism
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Two possible cases of an oxidative electron-transfer chain catalysis mechanism, the SON2 mechanism, are presented: the anionic 'oxidation' of 4-fluoroanisole in the presence of acetate ion to give 4-acetoxyanisole, and the CuIII 'oxidation' of chloro- and fluoro-benzene in the presence of water to give phenol.
- Eberson, Lennart,Joensson, Lennart
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p. 1187 - 1188
(2007/10/02)
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