Magnesium, organo- compounds preparation

Anhydrous diethyl ether is the customary solvent used when preparing organo magnesium compounds Sometimes the reaction does not begin readily but once started It IS exothermic and maintains the temperature of the reaction mixture at the boiling point of diethyl ether (35°C)... 

In many syntheses activation is not effected by sonochemical preparation of the metal alone but rather by sonication of a mixture of the metal and an organic reagent(s). The first example was published many years ago by Renaud, who reported the beneficial role of sonication in the preparation of organo-lithium, magnesium, and mercury compounds [86]. For many years, these important findings were not followed up but nowadays this approach is very common in sonochemistry. In another early example an ultrasonic probe (25 kHz) was used to accelerate the preparation of radical anions [87]. Unusually for this synthesis of benzoquinoline sodium species (5) the metal was used in the form of a cube attached to the horn and preparation times in diethyl ether were reduced from 48 h (reflux using sodium wire) to 45 min using ultrasound. 

These compounds are prepared by treating the sodium alloy of the metal with the required halogen compound, and in the case of tin two other methods are available, namely, the treatment of tin tetrachloride with sodium in the presence of the halogen organic compound, and the action of organo-magnesium compounds upon tin tetrachloride. 

Organo magnesium halides and organo lithium compounds are readily accessible alkylation and arylation reagents. However, they have little practical importance for the preparation of diorgano tellurium derivatives. Tellurium tetrachloride cannot be alkylated or arylated stepwise to give, for instance, diorgano tellurium dihalides, which could... 

Organo Vinyl Tellurium (from Vinyl Tellurium Iodides) A solution of the vinyl tellurium iodide, prepared by addition of 0.25 g (1.0 mmol) iodine in benzene to the divinyl ditelluride (1.0 mmol) in 5 ml tetrahydrofuran at 0° under nitrogen, is added dropwise to a solution of the organo magnesium bromide in 10 m/ tetrahydrofuran at 0°. The mixture is stirred at 20° for 1 h, hydrolyzed with a saturated aqueous solution of ammonium chloride, extracted with diethyl ether, the extract dried with magnesium sulfate and evaporated. The product is chromatographed on silica gel with petroleum ether (30-60°)/ethyl acetate (9 1) as eluent. The following compounds were prepared in this manner (yields in parentheses are for the reactions with vinyl tellurium iodides) ... 

Stable secondary enamines (21) may be prepared in aprotic media by partial methanolysis of organo-tin (32a), magnesium (32b) or lithium (32c) salts of imines and can be transferred from the reaction mixture under reduced pressure and trapped at —80 °C. These compounds are characterized by their NMR spectra and show a... 

To prepare our desired product (an ester), we must first synthesize the alcoholic portion of the ester (3-pentanol) from the starting material (ethanol). This can be done by a Grignard reaction. Grignard reagents (organo-magnesium compounds of the type R-Mg-X) will react with carbonyl compounds to produce alcohols upon hydrolysis. 

Like their aryl and alkenyl counterparts, alkynylboronic adds can be made by displacement of magnesium or lithium acetylides with borate esters. For example, Mat-teson and Peacock have described the preparation of dibutyl acetyleneboronate from ethynylmagnesium bromide and trimethyl borate [294]. The C-B hnkage is stable in neutral or acidic hydrolytic solvents but readily hydrolyzes in basic media such as aqueous sodium bicarbonate. Brown and co-workers eventually applied their organo-lithium route to boronic esters to the particular case of alkynylboronic esters, and in this way provided a fairly general access to this class of compounds [295]. 

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