Christinat Nicolas, Scopelliti Rosario, Severin Kay
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
J Org Chem. 2007 Mar 16;72(6):2192-200. doi: 10.1021/jo062607p. Epub 2007 Feb 22.
A new synthetic strategy for the construction of boron-based macrocycles and dendrimers is described. Condensation of aryl- and alkylboronic acids with 3,4-dihydroxypyridine is shown to give pentameric macrocycles in which five boronate esters are connected by dative B-N bonds. Three macrocycles have been characterized crystallographically. The boron atoms of these assemblies represent chiral centers, and the assembly process is highly diastereoselective. Attachment of amino or aldehyde groups in the meta position of the arylboronic acid building blocks does not interfere with macrocyclization. This allows performing multicomponent assembly reactions between functionalized boronic acids, dihydroxypyridine ligands, and amines or aldehydes, respectively. Reaction of 3,5-diformylphenylboronic acid, 3,4-dihydroxypyridine, and a primary amine R-NH2 (R=Ph, Bn) gives dendritic nanostructures having a pentameric macrocyclic core and 10 amine-derived R groups in their periphery. Combination of 3,5-diformylphenylboronic acid with 2,3-dihydroxypyridine and the dendron 3,5-(benzyloxy)benzylamine, on the other hand, results in formation of a dendrimer with a tetrameric macrocyclic core and eight dendrons in its periphery.
本文描述了一种构建硼基大环化合物和树枝状聚合物的新合成策略。芳基硼酸和烷基硼酸与3,4 - 二羟基吡啶缩合可生成五聚体大环化合物，其中五个硼酸酯通过配位B - N键相连。已通过晶体学对三种大环化合物进行了表征。这些组装体中的硼原子代表手性中心，且组装过程具有高度的非对映选择性。在芳基硼酸结构单元的间位连接氨基或醛基并不影响大环化。这使得分别在功能化硼酸、二羟基吡啶配体与胺或醛之间能够进行多组分组装反应。3,5 - 二甲酰基苯基硼酸、3,4 - 二羟基吡啶与伯胺R - NH₂（R = Ph，Bn）反应可得到具有五聚体大环核心且其外围有10个胺衍生的R基团的树枝状纳米结构。另一方面，3,5 - 二甲酰基苯基硼酸与2,3 - 二羟基吡啶以及树枝单元3,5 -（苄氧基）苄胺结合，可形成具有四聚体大环核心且其外围有八个树枝单元的树枝状聚合物。
