Of aryl Grignard reagents

Formation of aryl Grignard reagents (Section 14 4) Aryl halides react with magnesium to form the corresponding arylmagnesium halide Aryl iodides are the most reac tive aryl fluorides the least A similar reaction occurs with lithium to give aryllithium reagents (Section 14 3)... 

The conversion of diarylthallium trifluoroacetates to aromatic iodides by treatment with molecular iodine is thus analogous to the well-known conversion of diarylmercury derivatives with iodine to a mixture of an aromatic iodide and an arylmercury iodide (134), but it is much more effective as a synthetic tool because of the spontaneous disproportionation to product of the intermediate arylthallium trifluoroacetate iodide. The present procedure thus provides a practical synthetic method for the ultimate conversion of aryl Grignard reagents to aromatic iodides. 

This phenol synthesis complements the analogous reaction (see below) from arylthallium ditrifluoroacetates (147). Although yields are only moderate, the procedure represents a viable conversion of aryl Grignard reagents to phenols. It is a practical method, however, only when the diarylthallium trifluoroacetate precursor is formed via the Grignard route the alternative synthesis via symmetrization of arylthallium ditrifluoroacetates is obviously circuitous, since the latter compounds may be converted directly to phenols. 

Scheme 29 Iron-catalyzed cross coupling reaction of aryl Grignard reagents with alkyl halides...

Biaryl synthesisThis reagent promotes coupling of aryl Grignard reagents to symmetrical biaryls in 70-95% yield with formation of allene and 3-aryl-2-chloropropene as co-products. The reaction is retarded by galvinoxyl and evidently involves an electron-transfer from the Grignard reagent to the dichloropropene. 

Subsequent addition of aryl Grignard reagents then provides the secondary alcohols 161, which easily undergo elimination under the conditions shown in the scheme to provide the 1,3-disubstituted allenes 162 in excellent yields (-90%). 

The classic caustic fusion of sulfonic acid salts has been used for preparing 2,6-dinaphthol and its derivatives. Other more recent procedures have employed the direct hydrolysis of aryl bromides and the oxidation of aryl Grignard reagents. ... 

Grignard reaction, addition of methyl-magnesium bromide to thiophos-phoryl chloride, 46,102 addition of aryl Grignard reagents to diphenylchlorophosphine, 49, 66 Grignard reagents, synthesis and utility of unsolvated, 47, 116 titration of, 48, 48... 

A catalyzed asymmetric alkylation of glutaric anhydrides has yet to appear. However, Fu has reported that stoichiometric amounts of sparteine efficiently mediate the addition of aryl Grignard reagents to 4-substituted glutaric anhydrides, providing the 5-ketoacids in good yields and excellent enantioselectivities ... 

Murdoch and coworkers carried out amination reactions of aryl Grignard reagents and aryllithiums with oximes using O-p-toluenesulfonyl tetraphenylcyclopentanone oxime (0-tosyltetracyclone oxime) 6g (Scheme 61). The imine is extracted with benzene, purified, and then converted to amine and oxime by reacting with excess hydroxylamine in aqueous pyridine at room temperature. Amines are obtained following acidic hydrolysis. 

Amination of aryl Grignard reagents without a Cu(I) catalyst could succeed using 3,3, 5,5 -tetrakis(triflnoromethyl)benzophenone 0-tosyloxime 6j as an amination reagent in tolnene (Scheme 64). ... 

Following these results with the salen complex, Bedford reported on the synthesis of a series of Fe(iii)-salen-type complexes and the use of one of them, 75 (Figure 14), for the coupling of aryl Grignard reagents with primary and secondary alkyl halides, in Et20 at 45 Fiirstner subsequently reported on the use of the tetrakis(ethylene)fer-... 

The behavior of BnMgBr (5d) is similar to that observed for compounds with higher alkyl groups, i.e. only the coupling product was detected and the earlier report on the additional formation of benzyl alcohol was not confirmed. On the other hand, reactions of Ar" radicals formed in the anodic oxidation of aryl Grignard reagents are different from those established for Aik, as is evident from the percent distribution of parent radicals in major products given in Table 7. 

C. Iron-catalyzed Heteroarylation of Aryl Grignard Reagents. 614... 

D. Iron-catalyzed Alkylation of Aryl Grignard Reagents. 615... 

When the phenyl-substituted alkynyl sulfone 42 is used as a substrate for the Cu-catalyzed carbomagnesiation, interesting nucleophile-dependent stereoselectivity is observed. While the use of allyl Grignard reagent results in a syn addition, the use of aryl Grignard reagent results in an awh -carbomagnesiation (Scheme 25). ... 

Formation of aryl Grignard reagents (Section 14.4) Aryl... 

F.2.2. Asymmetric Cross-Coupling of Aryl Grignard Reagents Forming Axially Chiral Biaryls... 

Iron-catalysed homo-coupling of aryl Grignard reagents has been successfully developed.96 A variety of aryl Grignard reagents have been efficiently converted into the corresponding symmetrical biaryls in the presence of FeCl3 and a stoichiometric amount of 1,2-dichloroethane as oxidant (Scheme 18). 

A new role of iron catalyst in the Grignard conjugate addition has been disclosed.97 It catalysed 1,6-addition of aryl Grignard reagents to 2,4-dienoates or -dienamines in a highly regio- and stereo-selective manner. 

C.-). (1985) Reaction of aryl Grignard reagents with hexahalobenzenes Novel arenes via multiple aryne sequence. The Journal of Organic Chemistry, 50, 5524—8. 

By means of an orfho-lithiation of suitably functionalized aromatics it is possible to obtain aryllithium compounds from halogen-free aromatics in a way and with a regioselectivity (Section 5.3.1) for which there is no analogy in the preparation of aryl Grignard reagents. 

The homocoupling of aryl Grignard reagents triggered by organic halides in the presence of catalytic quantities of cobalt chloride or other transition metal halogenides was studied initially by Kharasch and Fields in 1941 [36]. They... 

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