ATROPO-DIASTEREOSELECTIVE CLEAVAGE OF CONFIGURATIONALLY UNSTABLE BIARYL LACTONES WITH ALKALI METAL ACTIVATED PRIMARY 1-ARYLETHYLAMINES

Axially chiral biaryls with diastereomeric ratios of up to 95:5 are synthesized by highly atropo-selective cleavage of configurationally unstable, lactone-bridged biaryls with chiral metalated 1-arylethlamines (see scheme). This methodology permits optional preparation of each of the two atropisomers from the same lactone precursor just by the use of the appropiate amine reagent or its enantiomer for the ring-opening (atropo-divergence), and offers the possibility of recycling the minor isomer back to the lactone. The chiral 1-arylethyl(amine) group can subsequently split off without any loss of stereoinformation at the axis.