Yolk-shell-mesostructured silica was used as a support in the development of an active-site-isolated bifunctional catalyst that can mediate a sequential organic transformation. Herein, through immobilization, the location of two catalytic species is controlled: a base functionality is anchored in the channels of the outer silica shell and a chiral ruthenium/diamine functionality is anchored on the inner silica yolk. The result is a yolk-shell-mesostructured silica-supported active-site-isolated dual molecule catalyst. Structural analysis through solid-state carbon 13 C NMR spectroscopy reveals its well-defined single-site dual active centers. Electron microscopy investigations disclose its uniformly distributed mesoporous nanoparticles. As envisaged, this bifunctional catalyst enables a controllable aza-Michael addition/asymmetric transfer hydrogenation catalytic sequence, where the base-catalyzed aza-Michael addition of enones and amines to aryl-substituted β -secondary amino ketones is followed by a Ru-catalyzed asymmetric transfer hydrogenation. Various aryl-substituted γ-secondary amino alcohols are obtained in high yields and enantioselectivities via this one-pot enantioselective organic transformation. Furthermore, the heterogeneous catalyst can be applied in a continuous-flow process, which was shown to be particularly attractive for the practical preparation of aryl-substituted γ-secondary amino alcohols in an environmentally friendly medium.

中文翻译：

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用于对映选择性串联反应的卵黄壳介孔结构的二氧化硅支持的双分子催化剂。

卵黄-壳介孔结构的二氧化硅被用作支持活性位点分离的双功能催化剂的开发载体，该催化剂可介导顺序的有机转化。本文中，通过固定，控制了两种催化物质的位置：将碱性官能团锚定在二氧化硅外部壳的通道中，并且将手性钌/二胺官能团锚定在内部二氧化硅卵黄上。结果是卵黄-壳介孔结构的二氧化硅负载的活性部位分离的双分子催化剂。通过固态碳13 C NMR光谱进行的结构分析显示其定义明确的单中心双活性中心。电子显微镜研究揭示了其均匀分布的介孔纳米粒子。按照设想，该双功能催化剂实现了可控的氮杂-迈克尔加成/不对称转移加氢催化顺序，其中碱催化的烯酮和胺的氮杂-迈克尔加成到芳基取代的β-仲氨基酮上，随后是Ru催化的不对称转移加氢。通过这种一锅式对映选择性有机转化，可以高收率和对映选择性获得各种芳基取代的γ-仲氨基醇。此外，非均相催化剂可用于连续流方法中，这被证明对于在环境友好的介质中实际制备芳基取代的γ-仲氨基醇特别有吸引力。其中将烯酮和胺的碱催化的氮杂-迈克尔加成到芳基取代的β-仲氨基酮上，然后进行Ru催化的不对称转移氢化。通过这种一锅式对映选择性有机转化，可以高收率和对映选择性获得各种芳基取代的γ-仲氨基醇。此外，非均相催化剂可用于连续流方法中，这被证明对于在环境友好的介质中实际制备芳基取代的γ-仲氨基醇特别有吸引力。其中将烯酮和胺的碱催化的氮杂-迈克尔加成到芳基取代的β-仲氨基酮上，然后进行Ru催化的不对称转移氢化。通过这种一锅式对映选择性有机转化，可以高收率和对映选择性获得各种芳基取代的γ-仲氨基醇。此外，非均相催化剂可用于连续流方法中，这被证明对于在环境友好的介质中实际制备芳基取代的γ-仲氨基醇特别有吸引力。