Alkyl, amines magnesium halides

This is an extremely efficient reagent and is rapid in its action. Phosphoric oxide is difficult to handle, channels badly, is expensive and tends to form a protective syrupy coating on its surface. A preliminary drying with anhydrous magnesium sulphate, etc., should precede its use. Phosphoric oxide is only employed when extreme desiccation is required. It may be used for hydrocarbons, ethers, alkyl and aryl halides and nitriles, but not for alcohols, acids, amines and ketones. 

Ammonia and alkyl amines do not form complexes in aqueous solution, but the solid halides can give adducts of the type MC12-hNH3 and magnesium halides give complexes such as MgBr2py4. 

If the molecule contains hydroxyl, amine or other reactive groups, they must be protected, as the intermediate (an alkyl magnesium halide) can be destroyed by such groups. See Figure 12.11. 

Organophosphorus compounds find wide use in the chemical industry as catalysts, intermediates, complexes, and end-use products. Arylphosphines and phosphine oxides are often produced by the reaction of a preformed Grignard reagent with a halophosphine or phosphine oxide. Yields are reduced by the production of unwanted side-reaction products such as biaryls. These unwanted products are reduced when the reaction is conducted under Barbier conditions. When alkyl and aryl halides are reacted with magnesium metal, a trihalophosphine or phosphine oxide, a metal halide or amine catalyst, in THE benzene mixtures, at reflux, good yields of phosphines or phosphine oxides are obtained [74]. For example, triphenylphosphine can be prepared in a 97.2% yield from the reaction of bromobenzene, trichlorophosphine, magnesium metal, aluminum chloride, and sodium chloride in THF-benzene at 70 80 C. 

Sodium (metal). Used as a fine wire or as chips, for more completely drying ethers, saturated hydrocarbons and aromatic hydrocarbons which have been partially dried (for example with calcium chloride or magnesium sulfate). Unsuitable for acids, alcohols, alkyl halides, aldehydes, ketones, amines and esters. Reacts violently if water is present and can cause a fire with highly flammable liquids. 

A mixture of (triisopropyl phosphito)copper(I) bromide (17.6 g, 0.05 mol) and l-bromo-2,2-diphenylethylene (9.1 g, 0.035 mol) was heated at 200°C for 1 h under a nitrogen atmosphere in a flask equipped with a Vigreaux column topped by a Dean-Stark trap. The alkyl halide produced in the reaction was collected in the trap. After cooling, the reaction mixture was poured into toluene (60 ml), and ethylenedi-amine was added (5 ml). After filtering and washing the precipitate with toluene, the combined toluene solutions were washed with 10% hydrochloric acid (10 ml) and water (10 ml), dried over magnesium... 

The reactivities of alkyl halides are in the sequence RI > RBr > RCl and MeX > EtX > PrX. Benzyl hahde reactions with tin do not require catalysts (equation 2). For less reactive halides, the catalysts and promoters employed include metals (sodium, magnesium, zinc, or copper), Lewis bases (amines, triorganophosphines and -stibines, alcohols, or ethers), iodides, and onium salts (R4MX). The use of tin-sodimn alloys can result in tri- or tetraorganotin products. Electrochemical synthesis has also been reported, e.g. the formation of R2SnX2 from the oxidation of anodic tin by RX in benzene solution and the formation of ILtSn from RI (R = Me or NCCH2CH2) and cathodic tin. 

Besides ethers, other compounds that form similar adducts accelerate the reaction of magnesium with an alkyl halide examples are dialkyl derivatives of elements of the Sixth Group (sulfur, selenium, and tellurium) and tertiary amines such as dimethylaniline, diethylaniline, pyridine, and quinoline. 

Bedford also found that a catalytic amount of FeCh and simple amines, such as EtsN or DAB CO, can affect the arylation of alkyl halides in diethyl ether at elevated temperature (Equation 5.29). Treatmentofbromomethylcyclopropane with phenyl-magnesium bromide in the presence of FeCf and DABCO provided the rearranged acyclic product, suggesting the involvement of an alkyl radical intermediate (Equation 5.30) [37]. 

The order of reactivity of the alkyl halides is RI > RBr > RCl, and for a given halogen, MeX > EtX > PrX, etc. Sumio Matsuda and Hanio Matsuda in Osaka University found that magnesium and butanol, etc. are excellent catalysts for this reaction in 1960 as shown in eq. (10.9) [8-14]. Esters, ketones and amines easily react with tin in the presence of these catalysts and organotin compounds having a... 

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