Oxygen-carbon bonds organolithiums

When 2,2-diphenyl-l,3-dioxolane (410, R = Ph) was lithiated with lithium and a catalytic amount of naphthalene (4%) in THF at —40°C (see Section VI.F.l) and then reacted with an aldehyde as electrophile, intermediates 437 were generated. The further lithiation of these compounds at the same temperature cleaved the second benzylic carbon-oxygen bond giving new organolithium intermediates 438, and a second electrophile could be introduced to give 439, after hydrolysis. In these products, two different electrophilic fragments have been incorporated, so the starting material behaves as the 1,1-diphenylmethane dianion synthon (Scheme 122) °. 

The reductive lithiation of cyclic benzofused ethers, for example, 510, with 4,4 -di-/< rt-butylbiphenyl (DTBB) and lithium gives intermediate organolithiums, for example, 511 and 512, that can be quenched with a variety of electrophiles to give general products 513 and 514 (Scheme 92). The process is not synthetically useful for 4H-chromene as carbon-oxygen bond cleavage occurs in both directions <2002TL4907>. 

Cyclic alkyl aryl ethers lead also to functionalized organolithium compounds by reductive carbon-oxygen bond cleavage in arene-catalyzed lithiation process. Thus, the treatment of 2,3-dihydrobenzofuran (47) with an excess of lithium in the presence of a catalytic amount of DTBB in THF at 0°C gives the dianion (48) which after reaction with different carbonyl compounds and final hydrolysis with water leads to... 

In ether or tetrahydrofuran organolithium reagents cleave the silicon-oxygen bond in hexamethylphosphoramide, they react at the carbon atom. ... 

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