title: Enantiospecific Sn(II)- and Sn(IV)-catalyzed cycloadditions of aldehydes and donor-acceptor cyclopropanes.
abstract: A cycloaddition strategy for the synthesis of highly enantioenriched 2,5-cis-disubstituted tetrahydrofurans has been developed. In the presence of catalytic Sn(OTf)2 or SnCl4, a range of aldehydes will undergo formal [3 + 2] cycloadditions with a scalemic donor-acceptor cyclopropane to form optically active heterocycles. Mechanistic studies support an unusual SN2 attack by the aldehyde on the activated cyclopropane. Through this mechanism, stereochemical information contained in the cyclopropane is effectively transferred to the tetrahydrofuran products.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
authors.forename: Patrick D
authors.initials: PD
authors.lastname: Pohlhaus
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Johnson