title: Desymmetrizing reductive aldol cyclizations of enethioate derivatives of 1,3-diones catalyzed by a chiral copper hydride.
abstract: A range of enethioate derivatives of 1,3-diones underwent reductive aldol cyclizations catalyzed by a chiral copper hydride generated in situ from 5 mol% TaniaPhos (SL-T001-1), 5 mol% Cu(OAc)(2)·H(2)O, 5 mol% bipyridine and 2.0 equiv. of PhSiH(3), to furnish polycyclic β-hydroxythioester products bearing three newly established contiguous stereocenters, with >98:2 dr and in up to 94% yield and 98% ee. The use of an amine such as bipyridine or 2,6-lutidine as additive results in an increase of the overall reaction rate. The major bicyclic aldol product has all substituents cis and can be rationalized by a reductively generated (Z)-enolate reacting with the dione via a cyclic transition state.
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ou
authors.forename: Wing-Tak
authors.initials: WT
authors.lastname: Wong
authors.forename: Pauline
authors.initials: P
authors.lastname: Chiu