Alkylmagnesium reagent

Aryl-alkenyl cross-coupling is straightforward. Simple alkylmagnesium reagents (Me, Et, CH2SiMe3, etc.) can be easily involved in Ni-catalyzed cross-coupling (27),139,140 while more complex alkyl halides—particularly branched ones prone to /3-hydride elimination—require Pd catalysts with bidentate phosphines, such as dppf, to achieve good selectivity (Section 9.6.3.4.7). 

Compared to the enantioselective allylic alkylation using soft nucleophiles, the reaction with Grignard reagents has received much less attention. The first enantioselective copper-catalyzed allylic alkylation with alkylmagnesium reagents was reported in 1995 by the groups of Backvall, van Koten and coworkers (Scheme 13). ... 

Aryloxide (phenolate) ligands provide rigid and versatile ancillary ligand sets in order to study the multifunctional reactivity of alkylaluminum and alkylmagnesium reagents toward Ln-OR moieties. Several types of symmetrically substituted phenolate ligands — summarized in Chart 4 — were employed for the synthesis of a variety of heterobimetallic lanthanide(III) and lanthanide(II) metal complexes. Alkylation reactions revealed the preferred... 

Alkylmagnesium reagents react with 4-nitroanisole by different mechanisms, giving in THF at —70 °C a number of products. Oxidation by KMnOa in liquid NH3 affords, depending on the alkyl chain, mixtures of nitrosoanisol and 2-alkyl-4-nitroanisol.314... 

Other transmetallation reactions of silver halides or their complexes with phosphine ligands (e.g. [AgIP(Bu-w)3]) with alkylhthium and alkylmagnesium reagents confirm the fleeting stability of the alkylsilver compounds. In each case the composition of the AgR intermediates has been derived from the analysis of the products formed in their thermal decomposition. So far, representatives of the class of simple alkylsilver complexes have not been isolated in pure form. 

The reaction of alkylmagnesium reagents with di-r-butyl peroxide leads to alkyl r-butyl ether, t-butyl alcohol, and disproportionation products of the alkyl [96]. Mechanistic studies showed that the initial step is ET. This conclusion was i.a. based on a linear correlation of log rate with the oxidation potentials of the Grignard reagents. Reactions of peroxides are extremely sensitive to metal catalysis, but take place even when high-purity magnesium is used. 

Although alkylmagnesium reagents may be prepared in hydrocarbons like methylcyclohextme or ben/.ene 108, the common solvents used for Grignard reactions are diethyl ether (DBli) and tetrahydrofuran. In special cases use is made ol very strongly coordinating solvents like DMK. HMPT, or crown ethers 18,72,5I. ... 

When a branching point in the skeleton falls outside the reach of a functional group, one can rely on skeletal bond-forming reactions which do not require the presence of a functional group. A nearly ideal solution to this problem is provided by the transition metal-catalyzed coupling reactions of alkylzinc or alkylmagnesium reagents with alkyl iodides [2, 3,4,5] (Scheme 3.4). 

H Si(lll) is less likely than Cl Si(lll) to react with alkylmagnesium reagents according to the classic formulation of Grignard reaction. However, so far, many... 

Scheme 5.36 Ni-catalyzed cross-coupling of alkylmagnesium reagents with C(sp )-electrophiles having sulfur leaving groups [105, 105].

Scheme 5.42 Ni-catalyzed cross-coupling of secondary alkylmagnesium reagents with aryl...

Scheme 5.43 Ni-catalyzed cross-coupling of tertiary alkylmagnesium reagents with an aryl bromide [120, 121].

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