Creation of monomeric La complexes on apatite surfaces and their application as heterogeneous catalysts for Michael reactions
Creation of monomeric La complexes on apatite surfaces and their application as heterogeneous catalysts for Michael reactions
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DOI：
10.1039/b512030f
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发表时间：
2006-01
影响因子：
3.3
通讯作者：
K. Mori;M. Oshiba;Takayoshi Hara;T. Mizugaki;K. Ebitani;K. Kaneda
中科院分区：
文献类型：
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作者：
K. Mori;M. Oshiba;Takayoshi Hara;T. Mizugaki;K. Ebitani;K. Kaneda
使用阳离子交换方法，通过用 La(OTf)3 水溶液处理化学计量羟基磷灰石 (HAP: Ca10(PO4)6(OH)2)，La3+ 等摩尔取代 Ca2+，得到单体羟基磷灰石结合的 La 络合物 (LaHAP)。通过 XRD、XPS、IR 和 La K 边 XAFS 分析等物理化学表征证明，其表面生成了单体 La3+ 磷酸盐络合物。这种单体 La3+ 物质可作为 1,3-二羰基与烯酮在水性或无溶剂条件下发生 Michael 反应的有效多相催化剂。后处理程序很简单，废催化剂可以回收而不会损失任何催化活性。还使用手性有机配体改性的各种磷灰石催化剂研究了对不对称形式的进一步应用。研究发现，1-氧代茚满-2-甲酸甲酯与甲基乙烯基酮反应时，对映选择性取决于手性配体、溶剂和稀土金属三氟甲磺酸盐前体 (RE(OTf)3)。在优化的反应条件下，用 (R,R)-酒石酸改性的单体氟磷灰石结合的 La 配合物催化剂 (TA-LaFAP) 定量提供了高达 60% ee 的迈克尔加合物。
Using a cation-exchange method, an equimolar substitution of La3+ for Ca2+ occurred by the treatment of stoichiometric hydroxyapatite (HAP: Ca10(PO4)6(OH)2) with an aqueous solution of La(OTf)3, affording a monomeric hydroxyapatite-bound La complex (LaHAP). Physicochemical characterization by means of XRD, XPS, IR, and La K-edge XAFS analyses proved that a monomeric La3+ phosphate complex was generated on its surface. Such monomeric La3+ species function as an efficient heterogeneous catalyst for the Michael reaction of 1,3-dicarbonyls with enones under aqueous or solvent-free conditions. The work-up procedure is straightforward and the spent catalyst could be recycled without any loss of the catalytic activity. Further application to an asymmetric version was also investigated using various apatite catalysts modified with chiral organic ligands. Enantioselectivity was found to depend on the chiral ligand, solvent, and rare earth metal triflate precursor (RE(OTf)3) for the reaction of methyl 1-oxoindan-2-carboxylate with methyl vinyl ketone. Under optimized reaction conditions, a monomeric fluoroapatite-bound La complex catalyst modified with (R,R)-tartaric acid (TA-LaFAP) provided the Michael adduct quantitatively in up to 60% ee.