Grignard type compound

The reaction sequence shown in Scheme 4 is exceptional for the synthesis of a multisilylated cyclopentadiene involving six-fold silylation in the reaction of hexabromocyclopentadiene with dimethylchlorosilane and magnesium43. Grignard-type compounds are presumably the intermediates in this process. More simple is the formation of the Grignard compound pentamethylcyclopentadienylmagnesium bromide from the reaction of bromopentamethylcyclopentadiene with magnesium44. 

Metallic components of zinc, aluminium and magnesium (or their alloys) are unsuitable for service with bromomethane because of the formation of pyrophoric Grignard-type compounds. The Case History attributes a severe explosion to ignition of a bromomethane—air mixture by pyrophoric methylaluminium bromides produced by corrosion of an aluminium component. 

Organozinc compounds are widely used as reagents.4 A typical synthesis of a zinc organometallic compound is given by the reaction below, in which the Grignard-type compound CH3ZnI is an intermediate ... 

Zinc forms a variety of Grignard-type compounds, such as ethylzinc chloride, ethylzinc bromide, butylzinc chloride, and butylzinc iodide. 

Salts of Grignard type compounds Hydroxide Salt Hydroxide Hydroxide Hydroxide... 

Grignard type compounds of some lanthanide metals in the oxidation state +2 have been investigated by D.F. Evans et al. (1970, 1971). Europium, samarium and ytterbium react in tetrahydrofuran with alkyl and aryl iodides between —20 and + 30°C forming colored solutions containing mixtures of compounds, which give some Grignard-type reactions. Characterization of the compounds was done only by magnetic susceptibility measurements and some titrimetric analyses. 

With AX being a fluorocarbon, the corresponding intermediate M AX can be considered a Grignard-type compound with a general stracture shown in Scheme 6.1. 

Organic halides play a fundamental role in organic chemistry. These compounds are important precursors for carbocations, carbanions, radicals, and carbenes and thus serve as an important platform for organic functional group transformations. Many classical reactions involve the reactions of organic halides. Examples of these reactions include the nucleophilic substitution reactions, elimination reactions, Grignard-type reactions, various transition-metal catalyzed coupling reactions, carbene-related cyclopropanations reactions, and radical cyclization reactions. All these reactions can be carried out in aqueous media. 

In 1991, Li and Chan reported the use of indium to mediate Barbier-Grignard-type reactions in water (Eq. 8.49).108 When the allylation was mediated by indium in water, the reaction went smoothly at room temperature without any promoter, whereas the use of zinc and tin usually requires acid catalysis, heat, or sonication. The mildness of the reaction conditions makes it possible to use the indium method to allylate a methyl ketone in the presence of an acid-sensitive acetal functional group (Eq. 8.50). Furthermore, the coupling of ethyl 2-(bromomethyl)acrylate with carbonyl compounds proceeds equally well under the same reaction conditions, giving ready access to various hydroxyl acids including, for example, sialic acids. 

The development of the Grignard-type addition to carbonyl compounds mediated by transition metals would be of interest as the compatibility with a variety of functionality would be expected under the reaction conditions employed. One example has been reported on the addition of allyl halides to aldehydes in the presence of cobalt or nickel metal however, yields were low (up to 22%). Benzylic nickel halides prepared in situ by the oxidative addition of benzyl halides to metallic nickel were found to add to benzil and give the corresponding 3-hydroxyketones in high yields(46). The reaction appears to be quite general and will tolerate a wide range of functionality. 

Tin compounds can be produced by the Nalco-type reactions39 as well as by Cd and Zn mediated methods42,43. The use of organotin compounds in electrodically induced transmetallations has also been described in a study in which Grignard-type allylation of carbonyl compounds has been carried out by electrochemically recycled allyltin reagents44. 

Vinylchromium compounds (12,137).6 These compounds can be obtained by reaction of vinyl triflates with CrCl2 catalyzed by NiCl2 in DMF. They undergo selective Grignard-type addition to aldehydes. Some commercial sources of CrCl2 do not require a catalyst, presumably because they contain a metal contaminant. 

The Grignard-type allylation of carbonyl compounds has been performed in an... 

Barbier-Grignard-type reactions in water (Li, 1996) between aUyl hahdes and carbonyl compounds can be mediated by metals of tin, zinc, or indium. Usually the generation of the organometalhc reagent takes place in anhydrous organic solvents, but using softer metals allows this reaction to take place in water. 

SCHORIG1N (or Shorygin) REACTION. Organometallic reactions of the Grignard type, employing sodium in place of magnesium the reaction of alkyl sodium compounds with carbon dioxide to give monobasic acids is sometimes known as the Wanklyn reaction. 

Application of the alcohol interchange reaction (method 6) is limited by certain phenols and also di and trisubstituted glyoxides (while the reaction of metals with glycols gives only monosubstituted derivatives) [745, 621, 575, 1584,1369]. As redox processes (method 7) can be considered the Grignard-type reactions — the interaction of metal alkyls with carbonyl compounds,... 

Grignard-type Addition of Acetylenic Compounds to Imines... 

Bacteria, antimicrobials against, 12, 456 Baeyer-Villiger oxidation, via tin amides, 9, 370 Barbier-Grignard-type reactions, and sonochemical metal insertions, 1, 315 Barbier-type reactions allenyl and propargyl tins, 9, 358 with allylic tins, 9, 357 with antimony(III) compounds, 9, 426 with bismuth(III) compounds, 9, 433 with cerium reagents, 10, 409 with indium compounds, 9, 685... 

The synthetic drawbacks of amino-substituted reagents are not observed when using resonance stabilized carbanions such as a-deprotonated nitriles 77) and carbonyl compounds 25), or allyl-21 and benzylmagnesium bromide 77), the corresponding very reactive tris-aminotitanium reagents undergoing rapid (—78 ° to —20 °C, 0.5 h) Grignard-type addition (80-95 % yields). 

The first system to be studied was 2-methyl-2-tolyl-cyclopentanone 168. In early 1979 we attempted to perform direct geminal dimethylation of this compound using dimethyltitanium dichloride 17114 in hope of obtaining curparene (Sect. F.II). Initial attempts were unsuccessful, since the product turned out to be the Grignard-type adducts 169 and 170 (Equation 57). 

III. Grignard-Type Addition Reactions of Organozinc Compounds. ... 

GRIGNARD-TYPE ADDITION REACTIONS OF ORGANOZINC COMPOUNDS... 

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