Butyllithium-Tetramethylethylenediamine

Hyperbranched polymers have also been prepared via living anionic polymerization. The reaction of poly(4-methylstyrene)-fo-polystyrene lithium with a small amount of divinylbenzene, afforded a star-block copolymer with 4-methylstyrene units in the periphery [200]. The methyl groups were subsequently metalated with s-butyllithium/tetramethylethylenediamine. The produced anions initiated the polymerization of a-methylstyrene (Scheme 109). From the radius of gyration to hydrodynamic radius ratio (0.96-1.1) it was concluded that the second generation polymers behaved like soft spheres. 

Another general way to prepare trimethylenemethane complexes is the reaction of trimethylenmethane dianions with metal halides. By this way. Mills et al. obtained (cyclopentadienyl)(trimethylenemethane)cobalt (21) in 18% yield by dilithiation of isobutene (19) with butyllithium/tetramethylethylenediamine (TMEDA) to dianion 20 [22,23] followed by treatment with 1 equiv. of (cyclopen-tadienyl)diiodo(triphenylphosphane)cobalt (Scheme 10.7). The crystal structure analysis shows a highly symmetric molecule with a slight pyramidalization of the trimethylenemethane ligand away from the cyclopentadienylcobalt... 

Competitive metallation experiments with IV-methylpyrrole and thiophene and with IV-methylindole and benzo[6]thiophene indicate that the sulfur-containing heterocycles react more rapidly with H-butyllithium in ether. The comparative reactivity of thiophene and furan with butyllithium depends on the metallation conditions. In hexane, furan reacts more rapidly than thiophene but in ether, in the presence of tetramethylethylenediamine (TMEDA), the order of reactivity is reversed (77JCS(P1)887). Competitive metallation experiments have established that dibenzofuran is more easily lithiated than dibenzothiophene, which in turn is more easily lithiated than A-ethylcarbazole. These compounds lose the proton bound to carbon 4 in dibenzofuran and dibenzothiophene and the equivalent proton (bound to carbon 1) in the carbazole (64JOM(2)304). 

The easiest access to most benzyllithium, -sodium, or -potassium derivatives consists of the deprotonation of the corresponding carbon acids. Hydrocarbons, such as toluene, exhibit a remarkably low kinetic acidity. Excess toluene (without further solvent) is converted into benzyllithium by the action of butyllithium in the presence of complexing diamines such as A. Af.Af.jV -tetramethylethylenediamine (TMEDA) or l,4-diazabicyclo[2.2.2]octane (DABCO) at elevated temperatures1 a procedure is published in reference 2. 

Treatment of the dialkylaminophosphines (39) with butyllithium and N,N -tetramethylethylenediamine results in predominant... 

B. N,N-Diethyl-2-formyl-6-methoxybenzamide (3). An oven-dried, threenecked, 1-L flask equipped with a 100-mL pressure equalizing dropping funnel, nitrogen bubbler, internal low temperature thermometer pocket, and overhead stirrer is flamed under reduced pressure and allowed to cool under a stream of nitrogen. The flask is charged with 500 mL of THF (Note 6) and cooled to an internal temperature of -72°C. N,N,N, N -Tetramethylethylenediamine (TMEDA) (Note 8) (23.5 mL, 0.156 mol) followed by 128.7 mL (0.157 mmol) of 1.22 M sec-butyllithium in cyclohexane (Note 9) are then added. The internal temperature rises a little as the reagents are added. The fluorescent yellow solution is allowed to recool to an Internal temperature of -73°C. 

Standard organolithium reagents such as butyllithium, ec-butyllithium or tert-butyllithium deprotonate rapidly, if not instantaneously, the relatively acidic hydrocarbons of the 1,4-diene, diaryhnethane, triarylmethane, fluorene, indene and cyclopentadiene families and all terminal acetylenes (1-alkynes) as well. Butyllithium alone is ineffective toward toluene but its coordination complex with A/ ,A/ ,iV, iV-tetramethylethylenediamine does produce benzyllithium in high yield when heated to 80 To introduce metal into less reactive hydrocarbons one has either to rely on neighboring group-assistance or to employ so-called superbases. 

Recently several studies have focused on the nature of the active species in the polymerization of ethylene and conjugated dienes initiated by the chelate of butyllithium and N,N,N, N -tetramethylethylenediamine (TMEDA). 

Both fragranol and grandisol skeletons were obtained by treatment of racemic butyl 6,7-epoxygeranyl sulfide with butyllithium in 7V,7V,Ar, 7V -tetramethylethylenediamine (TMEDA). In addition to the trans-product trans-16 (fragranol skeleton) and the ra-product m-16 (grandisol skeleton), a cyclopentane derivative was also isolated.16... 

SYNTHESIS A solution of 15 g 1,3-diethoxybenzene and 15 mL of N,N,N ,N -tetramethylethylenediamine in 200 mL anhydrous Et20 was placed in a He atmosphere, magnetically stirred, and cooled to 0 °C with an ice bath. Over the course of 10 min there was added 63 mL of a 1.6 M solution of butyllithium in hexane, which produced a fine white precipitate. After an additional 15 min stirring, 20 mL of tributyl borate was added which dissolved the precipitate. The stirring was... 

SYNTHESIS A solution was madeof45.2gN,N,N ,N -tetramethylethylenediamine and 41.4 g of 1,3-dimethoxybenzene in 300 mL hexane. This was stirred vigorously under a He atmosphere and cooled to 0 °C with an external ice bath. There was added 225 mL of 1.6 M butyllithium in hexane which produced a white granular precipitate. The reaction mixture was stirred for 15 min. There was then added 38... 

SYNTHESIS A solution of 12.1 g N,N,N ,N -tetramethylethylenediamine and 16.6 g of 1,3-diethoxy benzene was made in 200 mL 30-60 °C petroleum ether. This was stirred vigorously under a N2 atmosphere and cooled to 0 °C with an external ice bath. There was added 66 mL of 1.6 M butyllithium in hexane. The stirred reaction mixture became a little cloudy and then gradually formed a white granular precipitate. This was brought to room temperature, stirred for 0.5 h, and returned again to 0 °C. There was added 9.45 g of dimethyl disulfide which converted the loose precipitate to a creamy texture. The reaction was exothermic. After being held 0.5 h at reflux temperature, the reaction mixture was added to 600 mL dilute H2S04. There was the immediate formation of white solids which were insoluble in either phase. The petroleum ether phase was separated, and the aqueous phase extracted... 

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