Novel Intramolecular Induction of Axial Chirality by a Centrally Chiral Element in the Biphenyl Series
The title induction has been observed in the reaction of achiral 2,2',6,6'-tetrakis(bromomethyl)biphenyl with centrally chiral ( R )-1-phenylethylamine, ( R )-1-(1-naphthyl)ethylamine and ( R )-1-(2-naphthyl)ethylamine. The ratio of the arising diastereomeric doubly bridged diamines and their thermodynamic stability have been determined. The diastereomer excess in the kinetically controlled reaction is solvent-dependent. The absolute configuration of the biphenyl twist in the products has been assigned on the basis of CD spectra and comparison with singly bridged biphenyl models of known sense of the twist.