Homo aryl Grignard reagents

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). 

Nagano T, Hayashi T (2005) Iron-catalyzed oxidative homo-coupling of aryl grignard reagents. Oig Lett 7 491—493... 

Similar variants of Ullmann-type reactions based on intra- as well as intermolecular homo-couplings of various arylmetallic reagents, beside aryllithiums, also aryl Grignard reagents, arylzincs etc. with copper(II) salts give intermediate diarylcopper(Il) reagents which subsequently produce respective biaryls, usually in good yields, see Chapter 7. 

Homo-coupling reaction of aryl Grignard reagents with FeC Preparation of biphenyl (8) [12/... 

Titanium tetrachloride-mediated homo-coupling of aryl Grignard reagents Preparation of 4,4 -dicyanobiphenyl (541) [Uj... 

Total basicity is measured by standard acid—base titration techniques. The activity divided by the total basicity should be greater than 90%. If it is not, then the Grignard reagent should be checked for unreacted alkyl or aryl haUde, homo-coupled product, hydrolysis products, and oxidation products. 

Microwaves have been used both in the preparation of the Grignard reagent and in the Kumada coupling [87] with aryl chlorides. It was noted in this reaction that more homo-coupling side-products were typically formed when microwaves were used as an activation source than when the reaction was performed using ultrasound at ambient temperature (Scheme 15.46) [82]. 

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