Synthesis, chemo-selective properties of substituted 9-aryl-9H-fluorenes from triarylcarbinols and enantiomerical kinetics of chiral 9-methoxy-11-(naphthalen-1-yl)-11H-benzo[a]fluorene

Abstract

9-Aryl-fluorenes were synthesized conveniently from triarylcarbinols in the presence of TsOH. Notably, the orientation of the intramolecular aromatic substitution reaction was dictated by the nature of the substituents on the aryl rings of triarylcarbinols, owing to electronic and conjugated effects. In particular, triarylcarbinols with (3-methoxy)phenyl and naphthalenyl groups formed benzo[a]fluorenes selectively. Moreover, 9-methoxy-11-(naphthalen-1-yl)-11H-benzo[a] fluorene (2g), with a center of chirality, exists as a mixture of diastereoisomers, due to the restricted rotation of a C–C single bond. First-order rate constants for the enantiomerization of 2g in DMSO were obtained over the temperature from 297 K to 393 K, and thermodynamic parameters were determined as ΔH^‡ = 99.7 kJ mol⁻¹, ΔS^‡_{373 K} = 37.7 J mol⁻¹ K⁻¹, and ΔG^‡_{373 K} = 85.6 kJ mol⁻¹ by Eyring plot analysis.