Stereolabile chiral biphenyl hybrids: Crystallization-induced dynamic atropselective resolution involving supramolecular interactions

Crystallization-induced dynamic atropselective resolutions of three simple chiral biphenyl hybrids, (1R,1′R)-1,1′-(biphenyl-2,2′-diyl) diethanol 1, (1R,1′R)-1,1′-(biphenyl-2,2′-diyl)bis(ethane-1,1- diyl)diacetate 2 and (1S,1′S)-1,1′-(biphenyl-2,2′-diyl)bis(2, 2′-dimethylpropan-1-ol) 3 were achieved. The axial chirality of the biphenyl backbones of 1-3 were found to be determined by (i) the steric bulkiness at the α position of the ortho-substituents, and (ii) the intermolecular interactions between the molecules. 1, which possesses the least sterically demanding methyl substituents, was found to form stereoselectively the S-atropisomer and gave enantiomerically pure supramolecular right-handed helices through strong and directional intermolecular hydrogen bonds in its crystal.