title: Asymmetric epoxidation of unfunctionalized alkenes catalyzed by sugar moiety-modified chiral salen-Mn(III) complexes.
abstract: Several chiral Schiff-base ligands with sugar moieties at C-3 (3') or C-5 (5') of salicylaldehyde were synthesized from reaction of salicylaldehyde derivatives with diamine. These ligands coordinated with Mn(III) to afford the corresponding chiral salen-Mn(III) complexes characterized by FT-IR, MS, and elementary analysis. These complexes were used as catalysts for the asymmetric epoxidation of unfunctionalized alkenes. Only weak enantioselectivity is induced by the chiral sugar moieties at C-3 (3') or C-5 (5') in the case of absence of chirality in the diimine bridge moiety. It was also shown that the sugars at C-5 (5') having the same rotation direction of polarized light as the diimine bridge in the catalyst could enhance the chiral induction in the asymmetric epoxidation, but the sugars with the opposite rotation direction would reduce the chiral induction.
authors.affiliation: School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, PR China. zhaojq@hebut.edu.cn
authors.forename: Jiquan
authors.initials: J
authors.lastname: Zhao
authors.forename: Yuecheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Furong
authors.initials: F
authors.lastname: Han
authors.forename: Shanshan
authors.initials: S
authors.lastname: Zhao
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D002384:Catalysis; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D005029:Ethylenediamines / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D000475:Alkenes; D002241:Carbohydrates; D004852:Epoxy Compounds; D005029:Ethylenediamines; D009942:Organometallic Compounds; C090577:N,N'-bis(salicylideneamino)ethane-manganese(II)