title: Reductive openings of benzylidene acetals. Kinetic studies of borane and alane activation by Lewis acids.
abstract: The reaction kinetics for a number of reductive openings of methyl 2,3-di-O-benzyl-4,6-O-benzylidene-alpha-D-glucopyranoside have been investigated. Openings to give free HO-6 (using BH(3) x THF-AlCl(3)-THF or LiAlH(4)-AlCl(3)-Et(2)O) follow first order kinetics, while reactions yielding free HO-4 (using BH(3) x NMe(3)-AlCl(3)-THF or BH(3) x NMe(3)-BF(3) x OEt(2)-THF) follow higher order kinetics. The addition of water to the BH(3) x NMe(3)-AlCl(3)-THF results in faster reactions. The BH(3) x SMe(2)-AlCl(3)-THF system constitutes a borderline case, yielding both free HO-6 (by a first order reaction) and free HO-4 (by a higher order reaction). These results correlate well with the concept of regioselectivity by activation of borane complexes.
authors.affiliation: Organic Chemistry, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
authors.forename: Richard
authors.initials: R
authors.lastname: Johnsson
authors.forename: Risto
authors.initials: R
authors.lastname: Cukalevski
authors.forename: Fanny
authors.initials: F
authors.lastname: Dragén
authors.forename: Damir
authors.initials: D
authors.lastname: Ivanisevic
authors.forename: Ida
authors.initials: I
authors.lastname: Johansson
authors.forename: Linn
authors.initials: L
authors.lastname: Petersson
authors.forename: Erika Elgstrand
authors.initials: EE
authors.lastname: Wettergren
authors.forename: Ka Bo
authors.initials: KB
authors.lastname: Yam
authors.forename: Beatrice
authors.initials: B
authors.lastname: Yang
authors.forename: Ulf
authors.initials: U
authors.lastname: Ellervik
mesh_terms: D000080:Acetals / Q000737:chemistry*; D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000737:chemistry; D001597:Benzylidene Compounds / Q000737:chemistry*; D001880:Boranes / Q000737:chemistry*; D002236:Carbohydrate Conformation; D002712:Chlorides / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D009844:Oligosaccharides / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D000080:Acetals; D017607:Aluminum Compounds; D001597:Benzylidene Compounds; D001880:Boranes; D002712:Chlorides; D009844:Oligosaccharides; D000077410:Aluminum Chloride