title: Diastereodivergent asymmetric sulfa-Michael additions of α-branched enones using a single chiral organic catalyst.
abstract: A significant limitation of modern asymmetric catalysis is that, when applied to processes that generate chiral molecules with multiple stereogenic centers in a single step, researchers cannot selectively access the full matrix of all possible stereoisomeric products. Mirror image products can be discretely provided by the enantiomeric pair of a chiral catalyst. But modulating the enforced sense of diastereoselectivity using a single catalyst is a largely unmet challenge. We document here the possibility of switching the catalytic functions of a chiral organic small molecule (a quinuclidine derivative with a pendant primary amine) by applying an external chemical stimulus, in order to induce diastereodivergent pathways. The strategy can fully control the stereochemistry of the asymmetric conjugate addition of alkyl thiols to α-substituted α,β-unsaturated ketones, a class of carbonyls that has never before succumbed to a catalytic approach. The judicious choice of acidic additives and reaction media switches the sense of the catalyst's diastereoselection, thereby affording either the syn or anti product with high enantioselectivity.
authors.affiliation: ICIQ, Institute of Chemical Research of Catalonia, Avenida Països Catalans 16-43007 Tarragona, Spain.
authors.forename: Xu
authors.initials: X
authors.lastname: Tian
authors.forename: Carlo
authors.initials: C
authors.lastname: Cassani
authors.forename: Yankai
authors.initials: Y
authors.lastname: Liu
authors.forename: Antonio
authors.initials: A
authors.lastname: Moran
authors.forename: Atsushi
authors.initials: A
authors.lastname: Urakawa
authors.forename: Patrizia
authors.initials: P
authors.lastname: Galzerano
authors.forename: Elena
authors.initials: E
authors.lastname: Arceo
authors.forename: Paolo
authors.initials: P
authors.lastname: Melchiorre
mesh_terms: D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000588:Amines; D007659:Ketones; D013438:Sulfhydryl Compounds