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 alpha 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.