Grignard reagents arylation with

Many years later, Fukuhara and Urabe showed that aryl Grignard reagents react with ethyl 2,4-dienoates or 2,4-dienamides, in the presence of iron salts, to give the 1,6-addition products (Scheme 60). This reaction is stereoselective and leads to the (Z)-trisubstituted olefins. 

Unactivated aryl iodides undergo the conversion Arl — ArCHj when treated with tris(diethylamino)sulfonium difluorotrimethylsilicate and a palladium catalyst.131 A number of methods, all catalyzed by palladium complexes, have been used to prepare unsymmetrical biaryls (see also 3-16). In these methods, aryl bromides or iodides are coupled with aryl Grignard reagents,152 with arylboronic acids ArB(OH)2,153 with aryltin compounds Ar-SnR3,154 and with arylmercury compounds.155 Unsymmetrical binaphthyls were synthesized by photochemically stimulated reaction of naphthyl iodides with naphthoxide ions in an SrnI reaction.156 Grignard reagents also couple with aryl halides without a palladium catalyst, by the benzyne mechanism.157 OS VI, 916 65, 108 66, 67. 

From a comparison of the coupling of alkyl bromides 1 with aryl Grignard reagents 2 with different catalysts it can be concluded that all provided essentially the same result, although the required reaction temperatures and times varied (Table 1, entries 1-3, 5, 6, 8, and 9). The catalytic system using 4 is the fastest of all. That the most electron-rich complex is the best electron donor to generate radicals is a likely explanation. An Fe(-II)/Fe(-I) manifold (17A-D) accounts for the observed results (Fig. 3, Table 1, entry 2). Whether other catalyst systems can reach this redox state under the reaction conditions remains open. However, other low-valent redox manifolds, such as the Fe(0)/Fe(I) or Fe(I)/Fe(II) manifolds (18A-D, 19A-D), are also viable and may account for the reactivity differences. 

These higher chlorides of silicon hydrolyze in the same way as does the tetrachloride, and they likewise undergo similar reactions with Grignard reagents and with sodium alkyls or aryls.30 Under some conditions, however, the silicon-silicon bond is cleaved by sodium.31 The silicon-silicon chains are destroyed by the action of aqueous alkalies, liberating hydrogen at the rate of one molecule of H2 per silicon-silicon bond, just as are the higher silanes. 

Synthetic applications requiring water-free conditions, such as reactions with Grignard reagents, aryl and alkyl aluminum... 

Amination. Aijyllithium or aryl Grignard reagents react with this reagent to form phosphoryltriazcnes, Which arc reduced by sodium bis(2-mcthoxycthoxy)aluminum hydride to amines (45-1 8% yield). 

Aryl Grignard reagents usually give better yields in these reactions than alkyl Grignard reagents. Aryl triflates couple with arylmagnesium halides in the presence... 

Grignard reagents couple with aryl hahdes without a palladium catalyst, by the benzyne mechanism, but an iron catalyzed coupling reaction was reported, " as... 

CO, BuaSnH, and NCCMe2N=NCMe2CN (AIBN). Aryl ketones can be prepared from aryltrimethylsilanes ArSiMea and acyl chlorides in the presence of AlCla Aryllithium and Grignard reagents react with iron pentacarbonyl to give aldehydes ArCHO. The reaction of CO with aryllithium may occur by electron transfer. ... 

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