Phenyl-(2-pyridyl)-(3-pyridyl)-(4-pyridyl)methane: Synthesis, Chiroptical Properties, and Theoretical Calculation of Its Absolute Configuration

The title compound, a prototypical chiral molecule based on a tetraarylmethane framework, has been synthesized in five steps from (2-pyridyl)-(3-pyridyl)ketone. X-ray crystallographic analysis revealed the tetraarylmethane framework of the molecule but did not determine the positions of the nitrogen atoms because the crystal is a racemic compound and the aryl groups are disordered in the crystal. The optical resolution of the title compound was achieved by chiral HPLC with a Chiralcel OD column. The CD spectra of the two fractions in acetonitrile exhibited opposite signs as expected for a pair of enantiomers. Their CD spectra are changed in 2m HCl due to protonation. The calculated CD curve for the target molecule based on time dependent density functional theory (TDDFT) reproduces the experimental result very well, thus suggesting that the first eluted fraction is the R isomer in terms of absolute configuration