Synthesis of Bridged Molecular Gyroscopes with Closed Topologies: Triple One-Pot Macrocyclization

We describe the synthesis and characterization of six bridged molecular gyroscopes with m-alkoxy-substituted trityl stators and dialkynylphenylene rotators. All of the bridged molecular gyroscopes were synthesized convergently to form the phenolic stator–rotator framework, while the alkyl and benzophenone bridges were installed in one step by relatively efficient one-pot reactions to form macrocyclic diether or diester linkages. The isolated yield per bond-forming reaction varied from ca. 42% to 80%, with one exception where macrocyclization failed to produce the desired product. The molecular structure and crystal packing of each of the bridged molecular gyroscopes were determined via single crystal X-ray diffraction. Like most molecular gyroscopes with open topologies previously studied, the singly bridged structures pack by interdigitating one trityl stator in one molecule next to the rotator of an adjacent molecule in the lattice. In contrast, the triply bridged molecular gyroscopes were found to pack in lamellar sheets that prevent the rotator–stator interdigitation of adjacent molecules. However, solvent molecules and conformationally flexible bridges tend to fill in the packing volume by collapsing next to the rotator or by extending one of their bridges into the cavity of a neighboring molecule.

本研究报道了六种桥联分子陀螺（bridged molecular gyroscopes）的合成与表征，该类分子以间位烷氧基取代三苯甲基（m-alkoxy-substituted trityl）为定子、二炔苯撑（dialkynylphenylene）为转子。所有桥联分子陀螺均通过汇聚式合成策略构建酚基定子-转子骨架，随后通过高效的一锅法反应一步引入烷基与二苯甲酮桥联基团，形成大环二醚或二酯连接结构。各成键反应的分离产率介于约42%至80%之间，仅一例因环化失败未获得目标产物。通过单晶X射线衍射（single crystal X-ray diffraction）确定了所有桥联分子陀螺的分子结构与晶体堆积方式。与此前报道的多数开放拓扑结构分子陀螺类似，单桥联分子陀螺的晶体堆积方式为：一个分子的三苯甲基定子与晶格中相邻分子的转子交错穿插。与之相反，三桥联分子陀螺则以层状片层结构堆积，该结构可阻止相邻分子间的转子-定子交错穿插。不过，溶剂分子与构象柔性的桥联基团往往会通过在转子附近塌陷，或是将其中一条桥联基团延伸至相邻分子的空腔中，来填补堆积空隙。