Magnesium organic halides

Thus, early theoretical and experimental studies of low-temperature reactions in the magnesium-organic halide films allowed one to formulate the problem of obtaining cluster Grignard reagents inaccessible for classical organometallic synthesis but provided no actual evidence of their formation and stabilization. 

What are the processes in magnesium-organic halide films that lead to stabilization of tetranuclear magnesium clusters ... 

As in the case of aldehydes, Barbier reactions of magnesium, organic halide and ketone can be an alternative to the reactions via preformed organomagnesium compounds [18, 53],... 

Metallic sodium. This metal is employed for the drying of ethers and of saturated and aromatic hydrocarbons. The bulk of the water should first be removed from the liquid or solution by a preliminary drying with anhydrous calcium chloride or magnesium sulphate. Sodium is most effective in the form of fine wire, which is forced directly into the liquid by means of a sodium press (see under Ether, Section II,47,i) a large surface is thus presented to the liquid. It cannot be used for any compound with which it reacts or which is affected by alkalis or is easily subject to reduction (due to the hydrogen evolved during the dehydration), viz., alcohols, acids, esters, organic halides, ketones, aldehydes, and some amines. 

Many organic halides do not react satisfactorily with lithium to form RLi ecMnpounds or with metallic magnesium to form Grignard reagents. The desired organolithium compound can often be prepared by a halogen-metal interconversion reaction ... 

Grignard reagents are prepared from organic halides by reaction with magnesium a Group II metal... 

A convenient method for generating carbon nucleophiles is to combine an organic halide, RX, with magnesium metal. This yields RMgX, a Grignard reagent . 

Polarization also occurs in coupling and disproportionation reactions of Grignard reagents with alkyl halides. The vinyl protons of isobutene produced in the reaction of t-butylmagnesium chloride with t-butyl bromide show A/E polarization as do the methyl protons of isobutane (Ward et al., 1970). Similar results arise in the reaction of diethyl-magnesium with organic halides (Kasukhin et al., 1972). 

The catalyst is not necessary either for the electrocarboxylation of aryl halides or various benzylic compounds when conducted in undivided cells and in the presence of a sacrificial anode of aluminum [105] or magnesium [8,106], Nevertheless both methods, i.e., catalysis and sacrificial anode, can be eventually associated in order to perform the electrocarboxylation of organic halides having functional groups which are not compatible with a direct electroreductive process. 

The third pathway (Scheme 1) for the preparation of heteroleptic monoorganomagne-sium compounds, especially monoorganomagnesium halides, involves the reaction of an organic halide with metalhc magnesium, the classical Grignard reaction (equation 14). 

The reaction of the organic halide with magnesium is carried out in a non-protic polar solvent, usually diethyl ether or THF. Typical by-products are RR, RH and R(-H) (alkene), resulting from coupling and disproportionation reactions of the organic moiety. Also, by-products resulting from solvent attack are sometimes formed, but usually to a lesser extent. 

The direct electrochemical synthesis (Scheme 2) of the addncts of organomagnesinm halides with 2,2 -bipyridine (6) and salts of organodihalogenomagnesinm(II) anions (7) was reported by Hayes and coworkers . Adducts of different stoichiometry and 7 were obtained in the electrochemical oxidation of magnesium in ACN solutions containing organic halides RX (8), a.ro-dihalides XR X (9) and 8 with ammonium salts R NX, respectively. All new products showed none of the typical reactions of Grignard reagents. 

A. Direct Oxidative Addition of Magnesium to Organic Halides. 512... 

A widely used route for the synthesis of Grignard reagents is the oxidative addition of magnesium metal to organic halides in a polar, aprotic solvent like THE or diethyl ether (equation 1). 

Unfortunately, the preparation of functionalized Grignard reagents via direct oxidative addition of magnesium metal to organic halides still suffers from severe limitations. This is mainly due to the intrinsic high reducing potential of magnesium metal. 

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