Fang Hao, García-Eguizábal Alejandro, Hsueh Yu Jen, Daniliuc Constantin G, Funes-Ardoiz Ignacio, Molloy John J
Department of Biomolecular Systems, Max-Planck-Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476, Potsdam, Germany.
Freie Universität Berlin, Arnimallee 22, 14195, Berlin, Germany.
Angew Chem Int Ed Engl. 2025 Feb 3;64(6):e202418651. doi: 10.1002/anie.202418651. Epub 2025 Jan 2.
Energy transfer catalysis (EnT) has had a profound impact on contemporary organic synthesis enabling the construction of higher in energy, complex molecules, via efficient access to the triplet excited state. Despite this, intermolecular reactivity, and the unique possibility to access several reaction pathways via a central triplet diradical has rendered control over reaction outcomes, an intractable challenge. Extended chromophores such as non-symmetrical dienes have the potential to undergo [2+2] cycloaddition, [4+2] cycloaddition or geometric isomerisation, which, in combination with other mechanistic considerations (site- and regioselectivity), results in chemical reactions that are challenging to regulate. Herein, we utilise boron as a tool to probe reactivity of non-symmetrical dienes under EnT catalysis, paying particular attention to the impact of boron hybridisation effects on the target reactivity. Through this, a highly site- and regioselective [2+2] cycloaddition was realised with the employed boron motif effecting reaction efficiency. Subtle modifications to the core scaffold enabled a [4+2] cycloaddition, while a counterintuitive regiodivergence was observed in geometric isomerisation versus [2+2] cycloaddition. The observed reactivity was validated via a mechanistic investigation, determining the origin of regiodivergence and reaction selectivity in competing EnT processes.
能量转移催化（EnT）对当代有机合成产生了深远影响，通过有效进入三重激发态，能够构建能量更高的复杂分子。尽管如此，分子间反应性以及通过中心三重态双自由基进入多种反应途径的独特可能性，使得控制反应结果成为一项棘手的挑战。诸如非对称二烯之类的扩展发色团有可能发生[2+2]环加成、[4+2]环加成或几何异构化，这与其他机理因素（位点和区域选择性）相结合，导致化学反应难以调控。在此，我们利用硼作为工具来探究非对称二烯在EnT催化下的反应性，特别关注硼杂化效应对目标反应性的影响。通过这一方法，利用所采用的硼基序实现了高效的位点和区域选择性[2+2]环加成，从而影响了反应效率。对核心支架进行细微修饰可实现[4+2]环加成，而在几何异构化与[2+2]环加成中观察到了违反直觉的区域发散现象。通过机理研究验证了所观察到的反应性，确定了竞争EnT过程中区域发散和反应选择性的起源。
