Magnesium organo-halides

Triorganylboranes were prepared in excellent yields [114] when magnesium reacted with the organo halide in the presence of Bp3-etherate under sonication ... 

Electroassisted Barbier Reactions. In Sect. 2.4 the so-called electro-assisted Barbier reaction was mentioned in which a wide range of alcohols were synthesized from organo halides, carbonyl compounds and a sacrificial magnesium anode. 

When magnesium was codeposited with organo halides, solvent-free Grignard reagents were obtained. The yields (determined by hydrolysis) for each of the following hahdes were ... 

Not only metallic zinc causes problems in its reactions with organo halides also magnesium and even more reactive metals such as lithium have their specific difficulties. 

Tissier and Grignard, in one of the earliest publications on Grignard chemistry [6], found that for the reaction of magnesium with bromobenzene, iodobenzene and analogous organo halides, the metal usually had to be activated by the addition of a crystal of iodine. 

Sachs and Ehrlich (vide supra p. 167) used bromoethane to facilitate the reaction with magnesium before the organo halide was applied of which an organomag-nesium derivative was desired. 

Ultrasound dramatically accelerated the formation of triorganylboranes [36] in a Barbier reaction of an organo halide, magnesium and BF3. etherate. Yields with various halides were... 

In general it can be stated that modern developments in the preparation of active magnesium have been extremely helpful to overcome starting problems of reactions of organo halides with this metal. 

Coupling of acetylenes and halides, copper-promoted, 50,100 Cuprous chloride, reaction with an organo-magnesium compound, 50,98... 

Similarly, nitroarenes can also be lithiated (Scheme 5.43), but reactions of meta-lated nitroarenes with electrophiles only proceed cleanly if the metalation is performed in the presence of the electrophile [403], Otherwise, the metalated arene can reduce nitro groups to nitroso groups, which quickly react with additional organo-metallic reagent to yield hydroxylamines [404, 405], Nitroarylmagnesium halides can be prepared by iodine-magnesium exchange at -80 °C to -40 °C, and react with electrophiles in the expected way [6] (Scheme 5.43). 

Many organo-metallic compounds can be preparod by digesting an ethereal solution of the magnesium alkyl or aryl halide with the metallic halogen coin- -pound. 

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... 

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