Atropo-Enantioselective Ring Cleavage of Lewis Acid Modified Biaryl Thionolactones†,‡

Attachment of an achiral, ruthenium-based Lewis acid fragment to configurationally unstable biaryl thionolactones 1a−1c, atropo-enantioselective reductive lactone cleavage of the resulting complexes with chiral hydride reagents, and subsequent decomplexation leads to axially chiral thioethers 3a−3c with enantiomeric ratios of up to 92:8.