title: Encapsulation of chiral Fe(salan) in nanocages with different microenvironments for asymmetric sulfide oxidation.
abstract: The solid catalysts for asymmetric oxidation of sulfides were prepared by encapsulating a chiral iron salan complex [Fe(salan)] in the nanocages of mesoporous silicas. The microenvironment of nanocages was finely tuned using silylation reagents with different kinds of organic groups, such as propyl (C3), 1-butyl-3-propyl-4,5-dihydroimidazolium bromide (ILBr), N-propyl-N,N,N-tri-n-butylammonium chloride (TBNCl) and N-propyl-N,N,N-tri-n-butylammonium bromide (TBNBr), and investigated by water and benzene adsorption. Fe(salan) encapsulated in the amphiphilic nanocage shows much higher enantioselectivity and activity than that in hydrophobic or hydrophilic nanocage for the asymmetric oxidation of thioanisole using H(2)O(2) as oxidant. The TOF of Fe(salan) encapsulated in the nanocage modified with TBNBr can reach as high as 220 h(-1), even higher than homogeneous Fe(salan) with a TOF of 112 h(-1). The enhanced catalytic activity is mainly due to the fast diffusion of H(2)O(2) and sulfide in the amphiphilic nanocage. The above results suggest that the microenvironment modification of the nanocage is an efficient method to synthesize highly efficient solid catalysts for asymmetric catalysis.
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinses Academy of Sciences, Dalian 116023, PR China.
authors.forename: Bo
authors.initials: B
authors.lastname: Li
authors.forename: Shiyang
authors.initials: S
authors.lastname: Bai
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Hengquan
authors.initials: H
authors.lastname: Yang
authors.forename: Qihua
authors.initials: Q
authors.lastname: Yang
authors.forename: Can
authors.initials: C
authors.lastname: Li
mesh_terms: D006861:Hydrogen Peroxide / Q000737:chemistry; D007202:Indicators and Reagents / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry*; D053769:Nanocapsules / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D016062:Porosity; D012822:Silicon Dioxide / Q000737:chemistry; D013237:Stereoisomerism; D013379:Substrate Specificity; D013440:Sulfides / Q000737:chemistry*
chemical_list: D007202:Indicators and Reagents; D058085:Iron Compounds; D053769:Nanocapsules; D016877:Oxidants; D013440:Sulfides; D012822:Silicon Dioxide; D006861:Hydrogen Peroxide