Grignard-type reactions various halides

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. 

Benzyl halides and allyl (propargyl) halides are structurally similar but have drastically different chemical reactivities in the aqueous Barbier-Grignard-type reactions. Although tribenzyl and dibenzyltin derivatives have been prepared in aqueous conditions since the 1960s, they do not add onto carbonyls, most likely because it is not possible to form a six-membered cyclic transition state with the carbonyl group in a two-componenf fashion. Still, zinc-mediated benzylation of carbonyl compounds in aqueous media was reported by Bieber et al. recently. The benzylation of 4-nitrobenzaldehyde could be controlled chemoselectively by using various phase transfer catalysts and metal reductants in water (Eq. 4.41). 2... 

Of the many organometallic compounds, only Grignard reagents are used for formation of C-N bonds. Alkyl- and aryl-magnesium halides undergo various types of reaction with nitrogen compounds,1216 but few of these have major importance. 

The reaction is applicable to various types of Grignard reagents (e.g. aryl, alkyl) and organic halides bearing a C pi-carbon (e.g. aryl, vinyl). The reactivity order of the halide component was found to be Ar—I > Ar-Br > Ar-Cl > Ar-F. Grignard reagents are equally prepared either in Et20 or in THF, however, the... 

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