The atropo-diastereoselective cleavage of lactone-bridged and thus configurationally unstable biaryls with chiral metal-activated 1-arylethylamines gives axially chiral biaryl amides in good yields and high atropo-diastereomeric ratios of up to 95:5. In this methodology, even the minor not desired rotational isomer can be recycled literally by recyclization back to the configurationally unstable lactone, and renewed stereoselective cleavage. Furthermore, by the use of the corresponding enantiomer of the N-nucleophile, the enantiomeric biaryl product is also attainable from the same lactone precursor ("atropo-divergence"). In addition, several methods have been developed to transform the amide function into a methyl or an aminomethylene group. All these options further enlarge the scope and the utility of the method elaborated.
Bringmann, Gerhard; Geisler, Joerg-Peter; Geuder, Torsten, Liebigs Annalen der Chemie, 1990, # 8, p. 795 - 805