Diastereodivergent Asymmetric Sulfa-Michael Additions of α-Branched Enones using a Single Chiral Organic Catalyst

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 alpha-substituted alpha,beta-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.