- Complex-Induced Proximity Effects and Dipole-Stabilized Carbanions: Kinetic Evidence for the Role of Complexes in the α'-Lithiations of Carboxamides
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The kinetics of the α'-lithiations of N,N-dimethyl-2,4,6-triisopropylbenzamide (4) and N,N-diethyl-2,4,6-triisopropylbenzamide (5) by sec-butyllithium (s-BuLi) in cyclohexane have been investigated.Direct observation of the reactant amide, the intermediate amide-lithium reagent complex(es), and the α'-lithiated products by stopped-flow infrared spectroscopy was used to investigate the initial rate constants as a fuction of reactant concentrations.At constant amide concentration the initial rate constant decreases sharply with increasing concentration of s-BuLi.This behavior is also observed in the presence of tetramethylethylene diamine (TMEDA).The major interaction of TMEDA with s-BuLi in cyclohexane is shown by cryoscopic measurements to be an addition of TMEDA to aggregated s-BuLi.Semiquantitative schemes constructed on the basis of the kinetic data suggest the presence of at least two reactive complexes and that complexes with more ligands are more reactive.The implications of these results are discussed.
- Hay, David R.,Song, Zhiguo,Smith, Stanley G.,Beak, Peter
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- Characterization of hexameric and octameric sec-butyllithium/sec-butoxide mixed aggregates
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Solution-state characterization of sec-butyllithium in [D 8]toluene was conducted by utilizing a variety of NMR spectroscopic experiments including diffusion-ordered NMR spectroscopy (DOSY) with diffusion-coefficient-formula-weight correlation analyses and other one- and two-dimensional NMR spectroscopic techniques. These results suggest that sec-butyllithium exists primarily as a tetramer/hexamer mixture in hydrocarbon solvents. However, the presence of roughly 2-5 % (by mol ratio) lithium sec-butoxide in both commercially available and laboratory-synthesized sec-butyllithium solutions due to the reaction with adventitious dioxygen will lead to the formation of a 1:5 sec-butoxide/sec-butyllithium mixed hexamer. A sec-butoxide/sec-butyllithium mixed octamer will emerge when the proportion of butoxide to butyllithium increases. Solutions of sec-butyllithium in [D 8]toluene and the aggregates in them were characterized by a variety of methods including diffusion-ordered NMR spectroscopy (DOSY) and other one- and two-dimensional NMR spectroscopic techniques.
- Su, Chicheung,Hopson, Russell,Williard, Paul G.
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- Method for industrially producing sec-butyl lithium
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The invention provides a method for industrially producing sec-butyl lithium. The method for industrially producing sec-butyl lithium comprises (1) replacing air with argon gas in a reaction kettle and adding a solvent. (2) The lithium particles are charged into a feeder, air is replaced with argon, and all the lithium particles are placed in the reaction vessel. (3) On stirring, 2 - chlorobutane and metallic lithium are added dropwise through a metering pump to control the reaction temperature through the reaction kettle jacket and 2 - chlorobutane feeding speed. (4) After incubation 2 - 4h, the reaction is hydraulically introduced into the intermediate tank with argon, and the excess metal lithium is left in the reaction vessel. (5) The material in the intermediate tank was passed to a filter to remove lithium chloride solids with argon gas, and the resulting colorless to pale yellow transparent clear liquid, i.e. sec-butyllithium solution. The method adopts excess metal lithium particles and 2 - chlorobutane in a solvent to react at a certain temperature to produce sec-butyl lithium, so that side reactions are effectively avoided, and the yield is improved.
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Paragraph 0019; 0026-0030
(2021/12/07)
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- Method for Preparing Diorganomagnesium-Containing Synthesis Means
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A diorganomagnesium-containing synthesis means, a method for its preparation and its use.
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Page/Page column 25-26
(2008/12/04)
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- METHOD FOR PRODUCING ALKYL LITHIUM COMPOUNDS AND ARYL LITHIUM COMPOUNDS BY MONITORING THE REACTION BY MEANS OF IR-SPECTROSCOPY
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The invention relates to a method for producing alkyl lithium compounds and aryl lithium compounds by reacting lithium metal with alkyl or aryl halogenides in a solvent, the concentration of the alkyl/aryl halogenide and the alkyl/aryl lithium compound being detected according to an in-line measurement in the reactor by means of IR spectroscopy, and an exact recognition of the end point of the dosing of the halogenide constituents being carried out by evaluation of the IR measurement. Said method enables an optimum reactive process and reaction yield. The identification of the respective concentration of the educt and the product is a reliable reactive process. The yield of the reaction is also optimised by determining the end point of the halogenide dosing, as is the purity of the product due to a lower concentration thereof during the reaction.
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Page/Page column 14-15
(2008/06/13)
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- Method for producing alkyl-bridged ligand systems and transition metal compounds
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The invention relates to a method for producing highly substituted alkyl-bridged ligand systems on the basis of indene derivatives and transition metal compounds. Said alkyl-bridged ligand systems can be obtained in high yields using this method.
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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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- Synthesis of cyclopropylacetylene
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The present invention relates generally to novel methods for the synthesis of cyclopropylacetylene which is a reagent in the asymmetric synthesis of (S)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one which is a useful human immunodeficiency virus (HIV) reverse transcriptase inhibitor.
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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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