title: Achiral counterion control of enantioselectivity in a Brønsted acid-catalyzed iodolactonization.
abstract: Highly enantioselective halolactonizations have been developed that employ a chiral proton catalyst-N-iodosuccinimide (NIS) reagent system in which the Brønsted acid is used at catalyst loadings as low as 1 mol %. An approach that modulates the achiral counterion (equimolar to the neutral chiral ligand-proton complex present at low catalyst loadings) to optimize the enantioselection is documented for the first time in this transformation. In this way, unsaturated carboxylic acids are converted to γ-lactones in high yields (up to 98% ee) using commercially available NIS.
authors.affiliation: Department of Chemistry and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, USA.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Dobish
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Johnston
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D006219:Halogens; D006586:Hexanes / Q000737:chemistry; D006860:Hydrogen Bonding; D007477:Ions; D008024:Ligands; D008956:Models, Chemical; D013237:Stereoisomerism; D013388:Succinimides / Q000737:chemistry; D013696:Temperature
chemical_list: D002264:Carboxylic Acids; D006219:Halogens; D006586:Hexanes; D007477:Ions; D008024:Ligands; D013388:Succinimides; C008155:N-iodosuccinimide