Light-driven [2+2] cycloaddition is the most direct strategy to build tetrasubstituted cyclobutanes, core components of many lead compounds for drug development. Significant advances in the chemoselectivity and enantioselectivity of [2+2] photocycloadditions have been made, but exceptional and tunable diastereoselectivity and regioselectivity (head-to-head versus head-to-tail adducts) is required for the synthesis of bioactive molecules. Here we show that colloidal quantum dots serve as visible-light chromophores, photocatalysts and reusable scaffolds for homo- and hetero-intermolecular [2+2] photocycloadditions of 4-vinylbenzoic acid derivatives, including aryl-conjugated alkenes, with up to 98% switchable regioselectivity and 98% diastereoselectivity for the previously minor syn-cyclobutane products. Transient absorption spectroscopy confirms that our system demonstrates catalysis triggered by triplet-triplet energy transfer from the quantum dot. The precisely controlled triplet energy levels of the quantum dot photocatalysts facilitate efficient and selective heterocoupling, a major challenge in direct cyclobutane synthesis.

中文翻译：

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量子点光催化的区域和非对映选择性分子间[2 + 2]环加成。

光驱动的[2 + 2]环加成反应是构建四取代的环丁烷的最直接方法，四取代的环丁烷是许多用于药物开发的先导化合物的核心成分。在[2 + 2]光环加成物的化学选择性和对映选择性方面取得了重大进展，但是合成生物活性分子需要优异且可调节的非对映选择性和区域选择性（头对头与头对尾加合物）。在这里我们表明，胶体量子点可作为可见光发色团，光催化剂和4-乙烯基苯甲酸衍生物（包括芳基共轭烯烃）的均分子和异分子[2 + 2]光环加成反应的可重复使用的支架，其中可转换的98％先前较小的顺式环丁烷产物具有较高的区域选择性和98％的非对映选择性。瞬态吸收光谱证实了我们的系统证明了三重态-三重态从量子点转移能量所触发的催化作用。量子点光催化剂的精确控制的三重态能级促进了高效和选择性的杂化，这是直接环丁烷合成的主要挑战。