Nguyen Hai Dang, Abe Manabu
Department of Chemistry, Graduate School of Advance Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Hiroshima, Japan.
Hiroshima Research Center for Photo-Drug-Delivery Systems (Hi-P-DDS), Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Hiroshima, Japan.
J Am Chem Soc. 2024 Apr 17;146(15):10993-11001. doi: 10.1021/jacs.4c02880. Epub 2024 Apr 5.
Photoreactions of (coumarin-4-yl)methyl derivatives have been extensively studied in many fields of chemistry, including organic synthesis and photoinduced drug delivery systems. The identification of the reaction intermediates involved in the photoreactions is crucial not only for elucidating the reaction mechanism but also for the application of the photoreactions. In this study, the photoreactions of 7-diethylamino(coumarin-4-yl)methyl thioester [-SC(O)CH], thionoester [-OC(S)CH], and ester [-OC(O)CH] were investigated to clarify the intermediary species and their chemical behavior. While a radical pair [i.e., 7-diethylamino(coumarin-4-yl)methyl radical and CHC(O)S] plays an important role in the photoreactions of and , an ion pair [i.e., 7-diethylamino(coumarin-4-yl)methyl cation, and CHCO] was the key in the photoreaction of . O-isotope-labeling of revealed a negligible recombination process within the ion pair. The unprecedented observation was rationalized by the open-shell character of the 7-diethylamino(coumarin-4-yl)methyl cation, whose formation was confirmed through product analysis and transient absorption spectroscopy.
（香豆素 - 4 - 基）甲基衍生物的光反应已在化学的许多领域中得到广泛研究，包括有机合成和光诱导药物递送系统。确定光反应中涉及的反应中间体不仅对于阐明反应机理至关重要，而且对于光反应的应用也很关键。在本研究中，对7 - 二乙氨基（香豆素 - 4 - 基）甲基硫酯[-SC(O)CH]、硫代酯[-OC(S)CH]和酯[-OC(O)CH]的光反应进行了研究，以阐明中间物种及其化学行为。虽然自由基对[即7 - 二乙氨基（香豆素 - 4 - 基）甲基自由基和CHC(O)S]在和的光反应中起重要作用，但离子对[即7 - 二乙氨基（香豆素 - 4 - 基）甲基阳离子和CHCO]是光反应的关键。的O - 同位素标记显示离子对内的重组过程可忽略不计。这一前所未有的观察结果通过7 - 二乙氨基（香豆素 - 4 - 基）甲基阳离子的开壳特征得到合理解释，其形成通过产物分析和瞬态吸收光谱得以证实。
