Rotational isomerism in fluorene derivatives XXII syntheses of 1-substituted 2'-methyl-9, 9'-bifluorenyl derivatives and structures of their stereoisomers

Several 1-substituted 2'-methyl-9-hydroxy-9, 9'-bifluorenyl derivatives (2) and 1-substituted 2'-methyl-9, 9'-bifluorenyl derivatives (3) (1-substituents: CH_3, F, Cl, Br, I, and OCH_3) were prepared. These derivatives were confirmed as the mixture of erythro- and threo-isomers by their ^1H-NMR spectra. Restricted rotation about the C(9)-C(9') bonds was not observed owing to their considerably stable structures.