Grignard reagents, aryl

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)... 

Anthocyanidins were first synthesi2ed by reaction of an aryl Grignard reagent with a coumarin (93). 

Especially in the early steps of the synthesis of a complex molecule, there are plenty of examples in which epoxides are allowed to react with organometallic reagents. In particular, treatment of enantiomerically pure terminal epoxides with alkyl-, alkenyl-, or aryl-Grignard reagents in the presence of catalytic amounts of a copper salt, corresponding cuprates, or metal acetylides via alanate chemistry, provides a general route to optically active substituted alcohols useful as valuable building blocks in complex syntheses. 

Organomercury compounds undergo a similar reaction. Alkyl and aryl Grignard reagents can be converted to carboxylic esters with Fe(CO)5 instead of CO. Amides have been prepared by the treatment of trialkyl or triarylboranes with CO and an imine, in the presence of catalytic amounts of cobalt carbonyl ... 

Cross-Coupling of Arylchloridcs with Aryl Grignard Reagents... 

CROSS-COUPLING OF ARYLCHLORIDES WITH ARYL GRIGNARD REAGENTS (KUMADA REACTION)... 

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. 

More typical examples are the amino ethers (3) used as anti-histamine or anti-Parkinson drugs according to the substituents. These are obviously derived from the alcohols (4) which are made from an aryl Grignard reagent and a benzaldehyde. Either starting material may bear the substituent X the choice can be made according to availability and so that side reactions are avoided,... 

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

Yasuda S, Yorimitsu H, Oshima K (2008) Synthesis of aryliron complexes by palladium-catalyzed transmetalation between [CpFe(CO)2l] and aryl Grignard reagents and their chemistry directed toward organic synthesis. Organometallics 27 4025 027 Jonas K, Schieferstein L (1979) Simple route to Li- or Zn-metalated r -cyclopentadien-yliron-olefin complexes. Angew Chem Int Ed Engl 18 549-550... 

The corresponding bromides and iodides show concentration-dependent behavior and in very dilute solutions they exist as monomers. In tetrahydrofuran, there is less tendency to aggregate, and several alkyl and aryl Grignard reagents have been found to be monomeric in this solvent. 

The order of reactivity of halides with magnesium is RI > RBr > RC1 (very few organomagnesium fluorides have been prepared), i) Aryl Grignard reagents are more easily prepared from aryl bromides and aryl iodides than from aryl chlorides, which react very sluggishly. 

Preparation of the chiral biphenyls and binaphthyls with high enantiose-lectivity can be achieved via substitution of an aromatic methoxyl group with an aryl Grignard reagent using oxazoline as the chiral auxiliary.38 Schemes 8-10 and 8 11 outline the asymmetric synthesis of such chiral biaryl compounds. 

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. ... 

The indirect oxidation of an aryl Grignard reagent through a boronic ester nearly doubles the yield of phenol obtained by direct oxidation and decreases the reaction time. I etrahydro-... 

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... 

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