Crystallization-Induced Dynamic Resolution of Stereolabile Biaryl Derivatives Involving Supramolecular Interactions

Dynamic atroposelective resolutions in mixed Cu­(II) complexes
derived
from stereolabile biphenyl-2,2′-diol and enantiopure 1,2-diamines
have been achieved by crystallization. In these cases, all 2,2′-disubstituted
biphenyl fragments in the crystal have the same configuration at the
stereogenic axis as a result of the transmission of chirality at the
molecular level from the chiral inducer (enantiopure diamine ligand)
to the dynamically racemic biaryl units by means of supramolecular
forces (metal–ligand and hydrogen bonding interactions). Stereoselective
synthetic strategies toward [Cu­(2,2′-biphenolate)­(1,2-diamine)]
complexes have been developed, and these derivatives have been characterized
and studied by X-ray diffraction. The formation of hydrogen bonds
in an intramolecular (between the biphenyl-2,2′-diol and diamine
moieties) and in an intermolecular (between the moieties of the copper
complex and cocrystallized methanol) way appears to be essential for
the induction of chirality.