Asymmetric 9-(1′-naphthyl)fluorenes: enantioselective synthesis, determination of absolute configuration and retention of axial chirality in the fluorenyl carbanions

The rotamers of 1-methyl-9-[2′-(methoxymethyl)-1′-naphthyl]fluorene 10 and 11 were synthesised enantioselectively via ligand coupling reactions of 1-(alkyl or arylsulfinyl)naphthalene-2-carboxylate esters with 1-methylfluorenyllithium and the absolute configurations established by a single crystal X-ray study of the (1R)-menthyl ester 4; deprotonation of 10 and 11 affords fluorenyl carbanions, ent-12 and 12, respectively, which retain axial chirality.