Correlated Rotations in Benzylfluorene Derivatives: Structure, Conformation and Stereodynamics

Fluorene derivatives, having substituted benzyl groups bonded to position 9, have been investigated by variable temperature NMR spectroscopy. Stereodynamic processes involving restricted rotation about the fluorenyl-CH2 and aryl-CH2 bonds have been observed, leading to conformers and enantiomeric forms, and the corresponding barriers determined by line shape simulation. These dynamic processes are interpreted as due to correlated rotation pathways, on the basis of DFT computations that satisfactorily reproduce the experimental barriers. The structures of two such compounds were also determined by single crystal X-ray diffraction