Abstract The asymmetric photocatalytic organic synthesis (APOS) process is a sustainable and environmentally benign method for the production of optically active chemicals with sunlight as an energy source. However, it still lacks efficient semiconductors with tunable band structures and has a low recycling stability. Herein, we report the synthesis of tetrahydroquinoline-linked covalent organic frameworks (QH-COFs) with irreversible tetrahydroquinoline linkage as efficient semiconductors for the visible-light-driven asymmetric α-alkylation of aldehydes by merging with a chiral secondary amine. Up to 94% ee was obtained over QH-COFs, and the activity of QH-COFs was significantly higher than those of inorganic semiconductors (e.g., TiO2, BiVO4, and WO3) under similar conditions, which is mainly attributed to their narrow band gap and suitable band edge. As far as we know, QH-COFs are the most active semiconductors for asymmetric α-alkylation of aldehydes ever reported. The QH-COFs were prepared via a one-pot Povarov cascade imine formation and cycloaddition reaction using Sc(OTf)3/Yb(OTf)3 as Lewis acid catalysts. Attributed to the tetrahydroquinoline linkage, QH-COFs showed extremely high recycling stability, which made practicals application possible. This work not only opens up a new avenue for asymmetric photocatalysis but also provides an efficient and general method for the construction of robust COFs.

中文翻译：

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具有四氢喹啉键的稳健共价有机骨架上的不对称光催化

摘要 不对称光催化有机合成 (APOS) 工艺是一种可持续且环境友好的方法，用于以阳光为能源生产光学活性化学品。然而，它仍然缺乏具有可调能带结构的高效半导体，并且循环稳定性低。在此，我们报告了四氢喹啉连接的共价有机骨架 (QH-COFs) 的合成，该骨架具有不可逆的四氢喹啉键，通过与手性仲胺合并，作为可见光驱动的醛不对称 α-烷基化的有效半导体。在 QH-COFs 上获得了高达 94% 的 ee，并且在类似条件下，QH-COFs 的活性显着高于无机半导体（如 TiO2、BiVO4 和 WO3）的活性，这主要归功于它们的窄带隙和合适的带边。据我们所知，QH-COFs 是迄今为止报道的醛不对称 α-烷基化反应最活跃的半导体。QH-COFs 是通过一锅 Povarov 级联亚胺形成和环加成反应制备的，使用 Sc(OTf)3/Yb(OTf)3 作为路易斯酸催化剂。由于四氢喹啉键，QH-COFs表现出极高的循环稳定性，这使得实际应用成为可能。这项工作不仅为不对称光催化开辟了一条新途径，而且为构建稳健的 COF 提供了一种有效且通用的方法。QH-COFs 是通过一锅 Povarov 级联亚胺形成和环加成反应制备的，使用 Sc(OTf)3/Yb(OTf)3 作为路易斯酸催化剂。由于四氢喹啉键，QH-COFs表现出极高的循环稳定性，这使得实际应用成为可能。这项工作不仅为不对称光催化开辟了一条新途径，而且为构建稳健的 COF 提供了一种有效且通用的方法。QH-COFs 是通过一锅 Povarov 级联亚胺形成和环加成反应制备的，使用 Sc(OTf)3/Yb(OTf)3 作为路易斯酸催化剂。由于四氢喹啉键，QH-COFs表现出极高的循环稳定性，这使得实际应用成为可能。这项工作不仅为不对称光催化开辟了一条新途径，而且为构建稳健的 COF 提供了一种有效且通用的方法。