Magnesium bromide diethyl etherate

Once the substrate is reduced by a LiDBB (4,4 -di-tert-butyl-biphenyllithium) solution, the transmetallation of the produced lithium enolate is performed with 1 equiv. of the complex magnesium bromide-diethyl ether (MgBr2, Et20) leading to the chelated (Z)-magnesium enolate (equation 25). 

Magnesium bromide diethyl etherate Magnesium, dibromo(ethyl ether)- (8) Magnesium, dibromo[1,1 -oxybis[ethane]]- (9) (29858-07-9)... 

A general procedure for the cycloaddition reactions of a-alkoxy aldehydes with Brassard s diene 7 using Eu(hfc), or magnesium bromide-diethyl ether complex as Lewis acid catalyst is given below. A comparison of substituent effects and catalyst influence is shown in the following table. 

Guindon investigated diastereoselective allylation reactions of alkyl halides and phenyl selenides using allylsilanes [68], For example, substrate 116 is allylated by allyltrimethylsilane in the presence of magnesium bromide diethyl etherate using triethylboranc as an initiator (Scheme 25). No tin is required in these reactions. 

Diastereoselective Aldol Reaction Mediated by Magnesium Bromide-Diethyl Ether Complex (Eq. (40)) [61c]... 

A solution of ketene trimethylsilyl acetal 76 (6.30 g, 24.9 mmol) in toluene (30 mL) and a solution of aldehyde 77 (8.10 g, 16.6 mmol) in toluene (30 mL) vere successively added to a suspension of magnesium bromide-diethyl ether complex (12.9 g, 49.9 mmol) in toluene (100 mL) at —19 °C. The reaction mixture vas stirred for 1 h at —19 °C then triethylamine (23 mL) and saturated aqueous NaHCOs vere added. The mixture vas extracted vith diethyl ether and the combined organic extracts vere vashed vith brine, dried over Na2S04, filtered, and concentrated. The crude product vas purified by column chromatography (silica gel, hexane-ethyl acetate, 9 1) to afford the aldol adduct 78 (9.60 g, 87%) as a colorless oil. 

With nonchelating Lewis acids the favored conformation 145 of the stannane bears the proton in plane with the double bond, thus following the aUyl-1,3-strain model - the attack at the aldehyde occurs at the re face. Chelating Lewis acids such as magnesium bromide diethyl etherate turn the benzyloxy group in plane with the double bond of 147 - the attack at the aldehyde is reversed, now taking place at the si face yielding the anti-syn product 142. 

Deacetylanisomycin (4) is synthesized using L-tartaric acid (1) as a precursor in 12% overall yield16. The key step is the diastereoselective addition of (4-methoxybenzyl)magnesium chloride to the C — N double bond of nitrone 2 at 0°C in the presence of 1 equivalent of ethylmagncsium-bromide diethyl ether complex in dichloromethane. This procedure affords a chromatograph-ically separable mixture of the hydroxylamines 3 a and 3 b in a diastereomeric ratio [(2R,35,4R)/ (25,35,47 )] 70 30 and 60% yield from 2. 

Raw stock magnesium chipping ethyl bromide (the boiling point is not less than 35 °C, d4° = 1.420- 1.445) diethyl ether (d420 0.714 0.715) benzene (the density is 0.8770-0.8791 g/cm3) tin tetrachloride (anhydrous, the boiling point is 114-115 °C) caprylic acid (the boiling point is 239-240 °C, d420 = 0.9089) potassium hydroxide (technical product). Ethyl bromide, diethyl ether and benzene are dried before use with calcium chloride. 

The production diagram of diethyl tin dicaprylate is given in Fig. 93. Before synthesis the whole system is washed, dried and pressurised with nitrogen (the pressure is 0.05 MPa). After that reactor 1 is loaded through a hatch with magnesium and several grams of crystalline iodine (the initiator of the reaction), the agitator is switched on and inverse cooler 4 is filled with water. Then the reactor is filled at room temperature with part of the reactive mixture (ethyl bromide, diethyl ether and benzene) from batch box 2 to stimulate the reaction. 

From the reaction of triphenylmethyl bromide with magnesium in diethyl ether/benzene and subsequent crystallization, crystals of... 

The alkyl iodides and most of the alkyl bromides studied reacted with magnesium in diethyl ether at almost identical rates (see Fig. 3). As can be seen, the rate of the Grignard reagent was least sensitive to the structure of the organic halide. The difference between the structure-reactivity profiles for the Grignard reagent and the... 

In comparison, primary alkyl bromides react under stirring with magnesium in diethyl ether at the limit of mass transport control. Root, K.S. Hill, C.L. Lawrence, L.M. Whitesides, G.M. /. Am. Chem. Soc. 1989, 111, 5405-5412. 

Both pentafluorophenylmagnesium iodide and bromide have been reported (40-43). Apparently these reagents are readily formed from the appropriate halide and magnesium in diethyl ether. Pentafluorophenyl magnesium bromide has been used to prepare (C6Fs)4Si (32% yield) and (C,Fs)3P(39.5 % yield), as well as several pentafluorophenyltin compounds (Section V, C). 

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