title: Asymmetric iodolactonization utilizing chiral squaramides.
abstract: Asymmetric iodolactonization of γ- and δ-unsaturated carboxylic acids has been explored in the presence of six different chiral organocatalysts 5-8. The catalyst 6b was found to facilitate the cyclization of 5-arylhex-5-enoic acids 1 to the corresponding iodolactones 2 with up to 96% ee. By this protocol, unsaturated carboxylic acids are converted enantioselectively to synthetically useful δ-lactones in high yields using commercially available NIS. Apparently, both hydrogen bonding and aryl/aryl interactions are important for efficient stereodifferentiation.
authors.affiliation: School of Pharmacy, Department of Pharmaceutical Chemistry, University of Oslo, P.O. Box 1068 Blindern, N-0316 Oslo, Norway.
authors.forename: Jørn E
authors.initials: JE
authors.lastname: Tungen
authors.forename: Jens M J
authors.initials: JM
authors.lastname: Nolsøe
authors.forename: Trond V
authors.initials: TV
authors.lastname: Hansen
mesh_terms: D015107:4-Butyrolactone / Q000138:chemical synthesis* / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D003503:Cyclobutanes / Q000737:chemistry*; D006847:Hydrocarbons, Iodinated / Q000138:chemical synthesis* / Q000737:chemistry; D006860:Hydrogen Bonding; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D002264:Carboxylic Acids; D003503:Cyclobutanes; D006847:Hydrocarbons, Iodinated; D015107:4-Butyrolactone; C030042:squaric acid