- Determination of the Basicities of Benzyl, Allyl, and tert-Butylpropargyl Anions by Anodic Oxidation of Organolithium Compounds
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Electrochemical oxidation potentials have been determined by using cyclic voltammetry and second-harmonic ac voltammetry for benzyllithium, allyllithium, tert-butylpropargyllithium, and triphenylmethyllithium in tetrahydrofuran/hexamethylphosphoramide.The
- Jaun, Bernhard,Schwarz, Joshua,Breslow, Ronald
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- Mechanism of the deprotonation reaction of alkyl benzyl ethers with n-butyllithium
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Kinetic study of the α-lithiation of benzyl methyl ether (BME) by nBuLi has revealed that increasing the concentration of the organolithium compound does not necessarily increase the reactivity, and this is a consequence of the reactivities of the differe
- Raposo, M. Luz,Fernandez-Nieto, Fernando,Garcia-Rio, Luis,Rodriguez-Dafonte,Paleo, M. Rita,Sardina, F. Javier
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p. 9677 - 9685
(2013/07/26)
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- 6,12-Diphenyldibenzo[b,f][1,5]diazocine as an electron-capture agent: Efficient mechanistic probe for SET processes and reagent for the oxidative dimerization of benzylic organometallics
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In the present study, 6,12-diphenyldibenzo[b,f][1,5]diazocine, which X-ray diffraction measurements have now shown to possess a tub-shaped, eight-membered central ring, has been treated with sodium or lithium metal at 25 °C in THF, in an attempt to form the planar, Hueckel-aromatic dianion by the addition of two electrons to the central diazocine. Hydrolysis of such an aromatic dianion should have led to the isomeric 5,12- or 5,6-dihydro derivative of the original diazocine. In actuality, the only product obtained quantitatively upon hydrolytic workup was the interesting quadricyclic transannular reduction product, 4b,9b-diphenyl-4b,5,9b,10-tetrahydroindolo[3,2-b]indole, whose 3D structure has now been confirmed by X-ray crystallography and 13C NMR spectroscopy. Preferential SET transannular reduction of the diazocine to yield the quadricyclic indolo[3,2-b]indole dianion, rather than the planar, Hueckel-aromatic anion, is ascribed to the transannular electronic stabilization operative in the tub-shaped diazocine radical-anion. The quantitative generation of the indolo[3,2-b]indole dianion can be employed for the oxidative dimerization of the organic groups in benzylic lithium reagents. Thus treating one equivalent of the diazocine with two equivalents of benzyllithium, benzhydryllithium, or trityllithium yields quantitatively bibenzyl, 1,1,2,2-tetraphenylethane, or (4-benzhydrylphenyl)triphenylmethane, respectively. This oxidative dimerization is potentially of practical preparative scope, since the hydrolysis byproduct, the indolo[3,2-b]indole, is conveniently reconverted into the starting diazocine reagent by oxidation with chromium trioxide in acetic acid. The formation of the indolo[3,2-b]indole as a byproduct in the carbometalation of the diazocine by various RLi and Grignard reagents offers a clue as to the SET mechanism of carbometalation. Copyright
- Eisch, John J.,Yu, Kun,Rheingold, Arnold L.
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experimental part
p. 3165 - 3171
(2012/06/30)
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- 7Li, 31P, and1H pulsed Gradient Spin-Echo (PGSE) diffusion NMR spectroscopy and ion pairing: On the temperature dependence of the ion pairing in Li(CPh3), fluorenyllithium, and Li[N(SiMe 3)2] amongst other salts
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7Li, 31P, and 1H variable-temperature pulsed gradient spin-echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2-lithio-1,3-dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low-temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well-separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent-separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion.
- Fernandez, Ignacio,Martinez-Viviente, Eloisa,Breher, Frank,Pregosin, Paul S.
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p. 1495 - 1506
(2007/10/03)
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- Crystalline 10,10-Bis((2-fluoro-4-pyridinyl)methyl)-9(10H)-Anthracenone and an improved process for preparing the same
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The present invention relates to processes for the synthesis of a crystalline polymorph of 10,10-Bis((2-fluoro-4-pyridinyl)methyl)-9(10H)-Anthracenone in high purity. The product is useful in the synthesis of pharmaceutical compounds for the reduction of cholinergic system dysfunction.
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- Convergent synthesis of alpha -aryl- beta -ketonitriles
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The present invention relates to processes for the production of alpha -aryl- beta -ketonitriles, which serve as synthetic intermediates in the preparation of a series of biologically important molecules such as corticotropin releasing factor (CRF) receptor antagonists.
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- Sterically Hindered Free Radicals, XV The First Unsymmetrical Dimer from Two Different Stable Radicals: 3-(tert-Butylphenylmethylene)-6-(triphenylmethyl)-1,4-cyclohexadiene from tert-Butyldiphenylmethyl and Triphenylmethyl
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The quinonoid title compound 6 is formed in an equilibrium to 95percent and can be isolated, when the two title radicals 1 and 3 are generated in solution.The reason for this is the sterically less strained position of the bulky tBu group at the sp2
- Neumann, Wilhelm P.,Stapel, Ralf
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p. 2006 - 2012
(2007/10/02)
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- BESTIMMUNG DER IONENPAAR-BASIZITAT VON LITHIUM- UND KALIUMAMIDEN
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Ion pair basicities of lithio and potassio salts of some secondary amines were determined by equilibration with benzyl compounds.With these bases it is possible to span a range of about 19 pK-units from pK = 27 up to 46.The structural dependence of thermodynamic as well as kinetic basicity is discussed.Some new effective amide bases for preparative purposes are recommended.For the first time the pK-value of toluene has been determined by direct equilibration.It amounts to 40.7 in tetrahydrofuran.
- Ahlbrecht, Hubertus,Schneider, Gunther
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p. 4729 - 4742
(2007/10/02)
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