Conformational Control in Dirhodium(II) Paddlewheel Catalysts Supported by Chalcogen-Bonding Interactions for Stereoselective Intramolecular C–H Insertion Reactions

D2-symmetric dirhodium­(II) carboxylate catalysts that bear axially chiral binaphthothiophene δ-amino acid derivatives have been developed. Conformational control is supported through chalcogen-bonding interactions between sulfur and oxygen atoms in each ligand, providing well-defined and uniform asymmetric environments around the catalytically active Rh­(II) centers. These structural properties make such complexes asymmetric catalysts for the stereoselective intramolecular C–H insertion into α-aryl-α-diazoacetates to yield a variety of cis-α,β-diaryl γ-lactones, as well as the corresponding trans-isomers through epimerization, in high diastereo- and enantioselectivities. Short total syntheses of the naturally occurring γ-lactones, cinnamomumolide, cinncassin A7, and cinnamomulactone were also accomplished using this conformationally controlled catalyst.