Strategies for copper bis(oxazoline) immobilization onto porous silica based materials

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• 作者：Ana Rosa Silva^a ; ^{ana.rosa.silva@ua.pt} ; Hé ; lio Albuquerque^a ; Susana Borges^b ; René ; e Siegel^a ; Luí ; s Mafra^a ; Ana P. Carvalho^b ; Joã ; o Pires^b ;
• 关键词：Anchoring ; Mesoporous silicas ; Cyclopropanation ; Heterogeneous catalysis ; Asymmetric catalysis
• 刊名：Microporous and Mesoporous Materials
• 出版年：2012
• 期刊代码：78_13871811
• 类别：ch
• 出版时间：1 August, 2012
• 卷：158
• 期：Complete
• 页码：26-38
• 文件大小：1561 K

摘要

A copper(II) chiral bis(oxazoline) homogeneous catalyst (CuBox) was anchored onto mesoporous materials using three procedures: method 1, first anchoring of the bis(oxazoline) functionalized with 3-iodopropyltrimethoxysilane onto hexagonal mesoporous silica, SBA-15 and silica gel and then copper(II) coordination; method 2, anchoring of the CuBox functionalized with 3-iodopropyltrimethoxysilane onto hexagonal mesoporous silica, SBA-15 and silica gel; and method 3, first anchoring onto silica gel of 3-iodopropyltrimethoxysilane and then anchoring of the CuBox. In methods 1 and 3, the remaining free silanol groups of the silica materials were also capped using trimethylsilane groups. The bis(oxazoline) ligand was also encapsulated onto copper(II) exchanged zeolites NaY and NaUSY as a simpler strategy for the homogeneous catalyst immobilization, method 4. The materials were characterized by ICP-AES, elemental analyzes, ¹³C and ²⁹Si MAS NMR, FTIR, thermogravimetry and nitrogen adsorption at 鈭?96 掳C. The materials were tested as heterogeneous catalysts in the benchmark reaction of cyclopropanation of styrene to check the effect of the immobilization strategy on the catalytic parameters as well as on their reutilization in several catalytic cycles.