Dimers aryllithiums

Similarly to compound 164, sterically crowded aryllithium compounds such as 167 crystallize with the lithium atoms 7i -coordinated to aromatic rings. Compound 167b crystallizes as a dimer, with the lithium atoms coordinated to one of the phenyl substituents... 

Fig. 2. Structural types found for organolithiums containing internal—NMe2 donor centers (a) discrete tetrameric cubanes, e.g., an alkyllithium [(Me2NCH2CH2CH2Li)4 (28, 29)], an aryllithium [ (2-Me2NCH2)C6H4Li]4 (30), and an enolatolithium [(2-Me2NCH2)C6H4-C(=CH2)OLi]4 (31) (b) ring dimers, e.g., an alkyllithium...

Reich and coworkers have extended their studies of aryllithium compounds by use of pendant potential ligands28. They have identified equilibria between monomers and three kinds of internally solvated bridged dimers using a combination of 13C, 6Li and 15N NMR... 

PrLi)6], " and unsolvated lithium aryls are tetramers. cx-Ethoxyvinyllithium [CH2=C(OEt)Li] shows a polymeric structure with tetrameric subunits.Ami-nomethyl aryllithium reagents have been shown to be chelated and dimeric in solvents such as... 

Cu(N03)2. Alkyl- and aryllithium compounds can be dimerized by transition-metal halides in a reaction similar to 14-24. Triarylbismuth compounds ArsBi react with palladium(O) complexes to give biaryls ArAr. Diethylzinc reacted with Ph2l BF4 in the presence of palladium acetate, to give biphenyl. ... 

Dimeric aryl derivatives of Cr form by reactions of aryllithium compounds with CrCls. Chromium(II) products are formed from p-dimethylaminophenyl, o-anisole, and o-oxyphenyllithium reagents ... 

The portion of the product formed by reaction at C(l) in allylic systems may form by direct substitution, but it has also been suggested that a cyclic TS involving an aryllithium dimer might be involved. 

A convergent synthetic route to the highly symmetrical biphenylene dimer 61 was implemented based on a stepwise connection via an aryl-aryl homocoupling reaction. As can be seen in Scheme 5.9, after the lithiation of 1,3-dibromo-2-iodobenzenes 62 in diethyl ether, the resulting aryllithium was oxidized with CuBr2 to give the corresponding 2,6,2, 6 -tetrabromobiphenyls 63. Upon... 

SCHEME 3 Oxidative dimerization of an aryllithium intermediate in the synthesis of perylene-quinone natural products. 

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