title: Mechanistic dichotomy in the asymmetric allylation of aldehydes with allyltrichlorosilanes catalyzed by chiral pyridine N-oxides.
abstract: Detailed kinetic and computational investigation of the enantio- and diastereoselective allylation of aldehydes 1 with allyltrichlorosilanes 5, employing the pyridine N-oxides METHOX (9) and QUINOX (10) as chiral organocatalysts, indicate that the reaction can proceed through a dissociative (cationic) or associative (neutral) mechanism: METHOX apparently favors a pentacoordinate cationic transition state, while the less sterically demanding QUINOX is likely to operate via a hexacoordinate neutral complex. In both pathways, only one molecule of the catalyst is involved in the rate- and selectivity-determining step, which is supported by both experimental and computational data.
authors.affiliation: Department of Chemistry, WestChem, University of Glasgow, Glasgow G12 8QQ, UK. a.malkov@lboro.ac.uk
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Malkov
authors.forename: Sigitas
authors.initials: S
authors.lastname: Stončius
authors.forename: Mark
authors.initials: M
authors.lastname: Bell
authors.forename: Fabiomassimo
authors.initials: F
authors.lastname: Castelluzzo
authors.forename: Pedro
authors.initials: P
authors.lastname: Ramírez-López
authors.forename: Lada
authors.initials: L
authors.lastname: Biedermannová
authors.forename: Vratislav
authors.initials: V
authors.lastname: Langer
authors.forename: Lubomír
authors.initials: L
authors.lastname: Rulíšek
authors.forename: Pavel
authors.initials: P
authors.lastname: Kočovský
keywords: allylation; allylsilanes; calculations; organocatalysis; pyridine N-oxides