Chiral Nanoscale Metal-Organic Tetrahedral Cages: Diastereoselective Self-Assembly and Enantioselective Separation
Chiral Nanoscale Metal-Organic Tetrahedral Cages: Diastereoselective Self-Assembly and Enantioselective Separation
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手性纳米级金属有机四面体笼：非对映选择性自组装和对映选择性分离
DOI：
10.1002/anie.201000416
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Cui, Yong
中科院分区：
文献类型：
--
作者：
Liu, Taifeng;Liu, Yan;Cui, Yong
具有内腔的纳米级分子结构的自组装在过去十年中受到了广泛的关注。[1, 2] 这种空心多面体可以通过互补亚基的识别驱动自组装来合成。通过使用刚性、高度定向的多支化配体与配位不饱和金属配合物结合，合成了各种具有不同几何形状的高对称性笼和胶囊。[2-4]特别是，从Saalfrank等人的开创性工作开始，[3a]各种MxLy笼已由八面体金属中心和C2-或 C3 对称双和三（二齿）儿茶酚酰胺或 b-二酮配体。[3, 4] Raymond 及其同事描述了通过手性阳离子拆分外消旋阴离子 M4L6 簇。[4d] 将手性官能团纳入此类组装实体中可以扩展其在对映选择性过程中的效用。[5, 6] 然而， 基于手性空腔的不对称过程仍然相对未被探索，主要是因为合成光学纯形式的大型手性笼很困难。 [6]具有固有 C2 对称性的 1, 1'-联苯衍生物构成了一类广泛应用于手性识别过程的化合物，特别是作为不对称合成中的助剂。 [7]我们在此报告了由联苯桥配体 5, 5', 6, 6'-四甲基-3, 3'-二酮-2, 2'-双（甲氧基甲氧基）-联苯（H2L）和潜在的 C3 对称金属离子自组装出同手性四面体笼。该多面体可用作外消旋醇的结晶分离主体，对映选择性高达99.5%。由容易获得的手性5, 5', 6, 6'-四甲基-3, 3'-二叔丁基-1, 1'-联苯-2, 2'-二醇分四步制备对映纯阻转异构体H2L，总收率良好（32%） （方案1）。 H2L 与 MIII 氯化物（摩尔比为 3:2）在 DMF 中反应，然后将溶液与甲醇分层，以中等产率提供所需的配合物 M4L6（M= Fe 1, Ga 2）。四聚体的形成
The self-assembly of nanoscale molecular architectures that have inner cavities has received intense attention in the past decade.[1, 2] Such hollow polyhedra can be synthesized by recognition-driven self-assembly of complementary subunits. A variety of high-symmetry cages and capsules with distinct geometries have been synthesized with the use of rigid, highly directional multibranched ligands to bind to coordinatively unsaturated metal complexes.[2–4] In particular, starting with the pioneering work of Saalfrank et al.,[3a] a variety of MxLy cages have been assembled from octahedral metal centers and C2-or C3-symmetric bis-and tris (bidentate) catecholamide or b-diketonate ligands.[3, 4] The resolution of racemic anionic M4L6 clusters by chiral cations has been described by Raymond and co-workers.[4d] The incorporation of chiral functionalities into such assembled entities can expand their utility in enantioselective processes.[5, 6] Nevertheless, asymmetric processes based on chiral cavities still remain relatively unexplored, mainly because of the difficulty in synthesizing large chiral cages in optically pure forms.[6] 1, 1’-Biphenyl derivatives with intrinsic C2 symmetry constitute a class of compounds that are widely employed in chiral recognition processes, in particular as auxiliaries in asymmetric synthesis.[7] We report herein the self-assembly of homochiral tetrahedral cages from the biphenyl bridging ligand 5, 5’, 6, 6’-tetramethyl-3, 3’-diketone-2, 2’-bis (methoxymethoxy)-biphenyl (H2L), and potentially C3-symmetric metal ions. The polyhedra can be used as hosts for crystallization separation of racemic alcohols with an enantioselectivity of up to 99.5%.The enantiopure atropisomeric H2L was prepared in four steps in good overall yield (32%) from the readily available chiral 5, 5’, 6, 6’-tetramethyl-3, 3’-di-tert-butyl-1, 1’-biphenyl-2, 2’-diol (Scheme1). Reaction of H2L with MIII chloride (3: 2 molar ratio) in DMF followed by layering the solution with methanol afforded the desired complexes M4L6 (M= Fe 1, Ga 2) in moderate yields. The formation of the tetrameric