The Origin of Atropisomerism in 2,2′-Bis((1 R,2 R,4 S)-2-hydroxy-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl)-1,1′-biphenyl: Synthesis, Structure and Energetics

Abstract

In the X-ray crystal structure of 2,2′-bis((1 R,2 R,4 S)-2-hydroxy-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl)-1,1′-biphenyl ( 3- R) fenchyl alcohol units induce a R-sense of asymmetry at the biphenyl axis and support intramolecular hydrogen bonds between the hydroxy groups. Computational ONIOM evaluations of 3- R and of its diastereomer with S-biphenyl axis ( 3- S) reveal a higher stability (>6 kcal/mol) for 3- R and show how suitable alignments of 1,3,3-trimethylbicyclo[2.2.1]heptane units originate the observed R-biphenyl axis.