Tetramethylethylene diamine

Prepa.ra.tion, The preparation of amorphous high (99%) 1,2-polybutadiene was first reported iu 1981 (27). The use of a heterocycHc chelating diamine such as dipiperidine ethane iu the polymerization gave an amorphous elastomeric polymer of 99.9% 1,2 units and a glass-transition temperature of +5°C. In a previous description (53,54) of the use of a chelating diamine such as A/A/N(N -tetramethylethylene diamine, an 80% 1,2-polybutadiene with a glass-transition temperature of —30°C was produced. 

Moreover, a dramatic increase of the reaction rate was observed when the coupUng of aromatic imines mediated by samariiun diiodide was carried out in the presence of both water and a tertiary amine or tetramethylethylene-diamine (TMEDA) [29], causing the almost instantaneous formation of the 1,2-diamine, although with undetermined diastereoselectivity. Similarly, the samarium diiodide promoted reductive coupling of iminiiun ions formed in situ by reacting ahphatic aldehydes with secondary amines and benzotriazole occurred at temperatures as low as - 70 °C [30]. Even in this case a mixture of diastereomers with undetermined ratio was obtained nevertheless, the item of diastereoselectivity induced by a chiral amine (auxiliary) is worthy of investigation. 

The company Buckman Laboratories came out for the first time some 25 years ago with Polyquats. They were obtained by a reaction with a tertiary amine TMEDA (tetramethylethylene diamine), where the methyl groups can react easily with an ether. 

This approach frequently leads to the most active metals as the relatively short reduction times at low temperatures leads to reduced sintering of the metal particles and hence higher reactivity. Fujita, et aL(62) have recently shown that lithium naphthalide in tqluepe can be prepared by sonicating lithium, naphthalene, and N, N, N, N-tetramethylethylene-diamine (TMEDA) in toluene. This allows reductions of metal salts in hydrocarbon solvents. This proved to be especially beneficial with cadmium(49). An extension of this approach is to use the solid dilithium salt of the dianion of naphthalene. Use of this reducing agent in a hydrocarbon solvent is essential in the preparation of highly reactive uranium(54). This will be discussed in detail below. 

Ishikawa s endgame toward of 54 is shown in Scheme 3.12. First, the allylic alcohol function was oxidized by a substrate-directed dihydroxylation reaction, as developed by Donohoue and coworkers (66 % yield) [36]. This reaction is conducted using 1 equiv each of osmium tetroxide and tetramethylethylene diamine (TMEDA) and provides a method to obtain the syn-A i hydroxylation product in the... 

Other selected examples include tris(tetramethylethylene diamine-sodium)-9,9-dianthryl 143,154 alkali metal salts of 9,10-bis(diisopropylsilyl)anthracene 144,155 as well as the closely related naked 9,10-bis(trimethylsilyl)anthra-cene radical anion 145.156 This chemistry is further extended to the solvent-shared and solvent-separated alkali metal salts of perylene radical anions and dianions 146, 147,156 while other examples focus on alkali metal salts of 1,2-diphenylbenzene and tetraphenylethylene derivatives, where reduction with potassium in diglyme afforded contact molecules with extensive 7r-bonding, [l,2-Ph2C6H4K(diglyme)] 148.157 Extensive 7r-coordination is also observed in (1,1,4,4 tetraphenylbutadiene-2,3-diyl)tetracesiumbis(diglyme)bis(methoxyethanolate) 149.158... 

Phenylthio-l-trimethylsilylalkanes are easily prepared by the alkylation of (phenylthioXtrimethylsilyl)mcthane as shown in Scheme 10 [40], The treatment of (phenylthio)(trimethylsilyl)methane with butyllithium/tetramethylethylene-diamine (TMEDA) in hexane followed by the addition of alkyl halides or epoxides produces alkylation products which can be oxidized electrochemically to yield the acetals. Since acetals are readily hydrolyzed to aldehydes, (phenylthioXtrimethylsilyl)methane provides a synthon of the formyl anion. This is an alternative to the oxidative transformation of a-thiosilanes to aldehydes via Sila-Pummerer rearrangement under application of MCPBA as oxidant [40, 41]. 

Polymerization of the gel may be achieved either by ultraviolet photoactivation with riboflavin, or, preferably, using ammonium persulphate as a catalyst. It is necessary to include an initiator for the reaction, TEMED (tetramethylethylene diamine) being commonly used. 

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

The establishment of the stereocenter in efavirenz provides a challenging goal for the synthetic chemist (Pierce et al., 1998 Thompson et al., 1995). The synthesis starts by treating 4-chloroaniline with pivaloyl chloride under biphasic conditions to provide the desired amide 10 (Scheme 6.2). Ortho metallation as directed by the amide is accomplished with two equivalents of n-butyllithium (or w-hexyllithium) in tetramethylethylene diamine (TMEDA) and MTBE. The resulting dianion is quenched with ethyl trifluoroacetate to provide pivaloylamide ketone 11 (Euhrer and Gschwend, 1979). The amide is hydrolyzed in situ to provide the trifluoroketone hydrate hydrochloride 12, which crystallizes from the reaction mixture (>98% pure). 

Base-free dialkylmagnesium is sensitive to oxygen and reacts violently with water. It melts at 200-205°, though it does not sublime until 180° in vacuum. It is insoluble in benzene and petroleum ether, although it is readily soluble in diethyl ether and tetrahydrofuran. The diethyl ether solutions are conveniently stored at 0-5°. The titer does not change over a period of 1 month. The compound can be further characterized as its Af. /V)jV,jV,-tetramethylethylene-diamine complex, [Mg(Me3Si)CH2]2 tmed, mp 93-95°. 

Arylzinc species prepared via the sacrificial anode process and from aryl halides in the presence of a nickel 2,2 -bipyridine, as already reported in Section . .1, were found totally unreactive towards common electrophiles such as aldehydes, carboxylic anhydrides or activated alkyl halides. However, they react with some electrophiles when they are activated by the presence of a catalytic amount of copper salts (10 mol% Cul) together with tetramethylethylene diamine (1MEDA) as described by Knochel and Singer on the ArZnX—CuCN metal exchange47 or when the reaction is catalyzed by palladium complex. 

A Kjeldahl flask was charged with ,/V -dimethyl-1,6-diaminohexane (5.75 mmol) dissolved in 10 ml of THF and then treated with the dropwise addition of -butyl-lithium (5.75 mmol) while vigorously stirring. This solution was then treated with chlorotrimethylsilane (5.75 mmol) and stirred at ambient temperature for 30 minutes and then filtered off through a poly(tetrafluoroethylene) (PTFE) filter and 15 mL of the filtrate charged into a 150-ml glass bottle. This aliquot was then treated with tetramethylethylene diamine (4.23 mmol) and n-butyllithium (4.23 mmol) and used immediately as a polymerization initiator. 

At low ligand ratios using a mondentate amine, more than one species is probably present in solution and only at higher ligand ratios is most of the copper present in the active catalyst form. Since a bidentate amine like N,N,N, N -tetramethylethylene diamine forms a stable chelate in other systems, this may account for the reason that only a molar amount is necessary in this case. The first step in the reaction then appears to be (25), ... 

Lithiation Butyllithium, 56 /-Butyllithium, 58 Butyllithium-Tetramethylethylene-diamine, 57 Lithium, 157... 

Butylsodium-Tetramethylethylene-diamine, 59 Lithium hydride, 165 Potassium /-butoxide, 252 Potassium diisopropylamide, 255 Potassium hexamethyldisilazide, 257 Potassium hydride, 257 Methoxylation... 

Butyllithium-Tetramethylethylene-diamine, 212 Hexamethylditin, 142 Titanium(IV) isopropoxide, 165 Tributyltin chloride, 158, 315... 

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