School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China.
Dalton Trans. 2021 Jun 22;50(24):8533-8539. doi: 10.1039/d1dt00652e.
Visible-light-promoted [2 + 2] cycloaddition provides a straightforward and efficient way to produce cyclobutanes, which are the core skeleton in commercial pharmaceuticals and fine chemicals. However, the control of the conformation to produce syn-head-to-head (syn-HH) cyclobutanes remains a grand challenge. In this work, we report the design and synthesis of anthraquinone-based metal-organic cages (MOCs) for the [2 + 2] photocycloaddition of chalcones to generate syn-HH cyclobutanes. Guided by the coordination-driven self-assembly strategy, one D2 and three D4h symmetric MOCs are constructed from anthraquinone-derived dicarboxylate linkers and 4-tert-butylsulfonylcalixarene capped tetrametallic clusters. The porous cages feature large hydrophobic cavities and photoactive anthraquinone units and are demonstrated to be efficient and recyclable photocatalysts for [2 + 2] cycloaddition of chalcones. The syn-HH diastereomers are obtained with up to 13 : 1 diastereomeric ratio (dr). The cage catalysts provide a well-defined confined space to accommodate the substrates, thus leading to enhanced selectivity relative to the free anthraquinone catalyst.
可见光促进[2+2]环加成反应为生成环丁烷提供了一种直接且高效的方法，环丁烷是商业药物和精细化学品的核心骨架。然而，控制构象以生成顺-头对头（syn-HH）环丁烷仍然是一个巨大的挑战。在这项工作中，我们报告了基于蒽醌的金属-有机笼（MOC）的设计和合成，用于查耳酮的[2+2]光环加成反应以生成 syn-HH 环丁烷。受配位驱动的自组装策略的指导，由蒽醌衍生的二羧酸酯连接体和 4-叔丁基砜基杯[4]芳烃封端的四金属簇构建了一个 D2 和三个 D4h 对称的 MOC。多孔笼具有大的疏水性空腔和光活性的蒽醌单元，并被证明是查耳酮[2+2]环加成反应的高效且可回收的光催化剂。顺-HH 非对映异构体的产率高达 13:1 的非对映选择性（dr）。笼状催化剂提供了一个明确的受限空间来容纳底物，从而相对于游离蒽醌催化剂提高了选择性。
