Lithiophenylalkyllithiums: new dilithium reagents having both sp2- and sp3-hybridised remote carbanionic centres

The reaction of chloro-(2-chloroethyl)benzenes (1), 4-chloro-(3-chloropropyl)benzene (3) or 4-chlorophenyl chloromethyl ether (5) with lithium power using naphthalene as the electron shuttle (8 mol%) in the presence of different carbonyl compounds [ButCHO, PhCHO, Me2CO, Et2CO, (CH2)5CO, PhCOMe] in THF at −78 to 20 °C gives, after hydrolysis with water, the expected diols 2, 4 or 6, respectively. Bromo-2-(chloroethyl)benzenes (7) are treated with n-BuLi in THF at −100 °C, so the corresponding bromine–lithium exchanges takes place giving an intermediate, which is trapped by treatment with benzaldehyde or cyclohexanone, affording intermediates 9, which are submitted to a naphthalene-catalysed (8 mol%) lithiation with lithium power as above, followed by reaction with 3-pentanone and final hydrolysis with water, to give differently substituted diols 10. Some diols 2 are transformed into either the corresponding oxepane 11 or dienes 12 under Mitsunobu type conditions or by acidic treatment, respectively.