title: Ammonium-directed olefinic epoxidation: kinetic and mechanistic insights.
abstract: The ammonium-directed olefinic epoxidations of a range of differentially N-substituted cyclic allylic and homoallylic amines (derived from cyclopentene, cyclohexene, and cycloheptene) have been investigated, and the reaction kinetics have been analyzed. The results of these studies suggest that both the ring size and the identity of the substituents on nitrogen are important in determining both the overall rate and the stereochemical outcome of the epoxidation reaction. In general, secondary amines or tertiary amines with nonsterically demanding substituents on nitrogen are superior to tertiary amines with sterically demanding substituents on nitrogen in their ability to promote the oxidation reaction. Furthermore, in all cases examined, the ability of the (in situ formed) ammonium substituent to direct the stereochemical course of the epoxidation reaction is either comparable or superior to that of the analogous hydroxyl substituent. Much slower rates of ring-opening of the intermediate epoxides are observed in cyclopentene-derived and cycloheptene-derived allylic amines as compared with their cyclohexene-derived allylic and homoallylic amine counterparts, allowing for isolation of these intermediates in both of the former cases.
authors: Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
authors: Méabh B
authors: MB
authors: Brennan
authors: Timothy D W
authors: TD
authors: Claridge
authors: Richard G
authors: RG
authors: Compton
authors: Stephen G
authors: SG
authors: Davies
authors: Ai M
authors: AM
authors: Fletcher
authors: Martin C
authors: MC
authors: Henstridge
authors: David S
authors: DS
authors: Hewings
authors: Wataru
authors: W
authors: Kurosawa
authors: James A
authors: JA
authors: Lee
authors: Paul M
authors: PM
authors: Roberts
authors: Anne K
authors: AK
authors: Schoonen
authors: James E
authors: JE
authors: Thomson
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D007700:Kinetics; D015394:Molecular Structure; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D004852:Epoxy Compounds; D000644:Quaternary Ammonium Compounds