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Harnessing Chalcogen-bonding Interactions To Establish Conformational Control in Dirhodium(II) Paddlewheel Complexes
preprintsubmitted on 23.06.2020, 22:48 and posted on 25.06.2020, 12:12 by Takuya Murai, Wenjie Lu, Toshifumi Kuribayashi, Kazuhiro Morisaki, Yoshihiro Ueda, Shohei Hamada, Takahiro Sasamori, Norihiro Tokitoh, Takeo Kawabata, Takumi Furuta
Novel well-defined D2-symmetric dirhodium(II) carboxylate complexes that bear axially chiral binaphthothiophene delta-amino acid derivatives have been developed. Conformational control was achieved 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 render such complexes excellent catalysts for the inside-type asymmetric intramolecular C–H insertion into alpha-aryl-alpha-diazoacetates to yield a variety of cis- alpha, beta-diaryl gamma-lactones, as well as the corresponding trans-isomers through epimerization, in high diastereo- and enantioselectivities. Short total syntheses of the naturally occurring gamma-lactones cinnamomumolide, cinncassin A7, and cinnamomulactone were also accomplished using this conformationally controlled catalyst.