Mechanistic insights for the photoredox organocatalytic fluorination of aliphatic carbons by anthraquinone using time-resolved and DFT studies
Mechanistic insights for the photoredox organocatalytic fluorination of aliphatic carbons by anthraquinone using time-resolved and DFT studies
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DOI：
10.1039/c6cy02484j
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发表时间：
2017-02-21
影响因子：
5
通讯作者：
Tan, C. -H.
中科院分区：
文献类型：
--
作者：
Kee, J. W.;Shao, H.;Tan, C. -H.
化学选择性光氧化还原氟化是获得含氟精细化学品（如活性药物成分）的一种很有吸引力的方法，但目前大多数已知的方法缺乏时间解决的机制见解。我们使用纳秒瞬态吸收光谱和密度泛函理论（DFT）计算来阐明我们之前报道的光催化氟化过程中辐照后的基本步骤。时间分辨光谱学表明，光激发的蒽醌（AQN）与选择性氟(R)之间只发生直接反应。我们首次观察到一种新的瞬态aqn -选择氟(R)物种的光谱证据。通过DFT计算的进一步研究表明，光照射形成的aqn -选择性氟(R)三重态外络合物是引发和维持氟化反应的原因。
Chemoselective photoredox fluorination is an appealing approach to access fluorinated fine chemicals such as active pharmaceutical ingredients, but most of the known procedures currently lack time-resolved mechanistic insights. We use nanosecond transient absorption spectroscopy and density functional theory (DFT) calculations to elucidate the elementary steps after irradiation in a photocatalytic fluorination procedure that we reported previously. Time-resolved optical spectroscopy suggests that direct reaction only occurs between the photoexcited anthraquinone (AQN) and Selectfluor (R). We have observed spectroscopic evidence of a novel transient AQN-Selectfluor (R) species for the first time. Further studies by DFT calculations suggest that the AQN-Selectfluor (R) triplet exciplex formed by photoirradiation is responsible for initiating and sustaining the fluorination reaction.