The outcome of photosensitized [2+2]‐cycloaddition reactions of various cinnamates has been compared in different reaction media, including homogeneous organic solutions under inert conditions, degassed water, and aerated physical gels. The reactions were performed under LED blue light (λ_max=455 nm) irradiation and [Ir{dF(CF₃)ppy}₂(dtb‐bpy)]PF₆ (1.0 mol%) as photocatalyst. The processes were optimized taking into consideration solvent, gelator, and substrate. Comparative kinetics analyses, as well as the effect of the reaction media on the diastereoselectivity of the process, were evaluated during this investigation. In a number of cases, carrying out the reaction in a less polar solvent, like toluene or highly polar solvent, like water had a tremendous impact on the diastereoselectivity of the process, pointing towards an effect on the stabilization of the putative diradical intermediate in this medium. Moreover, while for reactions run in homogeneous solution oxygen needs to be excluded, no erosion in yield is observed when the photoadditions were run in aerated gel media.

中文翻译：

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反应介质对肉桂的光敏[2 + 2]-环加成反应的影响。

在不同的反应介质中，包括在惰性条件下的均相有机溶液，脱气水和充气的物理凝胶中，已比较了各种肉桂的光敏[2 + 2]-环加成反应的结果。反应在LED蓝光（_λmax = 455 nm）辐照和[Ir {dF（CF ₃）ppy} ₂（dtb-bpy）] PF _6下进行（1.0mol％）作为光催化剂。考虑到溶剂，胶凝剂和底物，对工艺进行了优化。在此研究过程中，评估了比较动力学分析以及反应介质对非对映选择性的影响。在许多情况下，在较低极性的溶剂（如甲苯或高极性的溶剂，如水）中进行反应，会对方法的非对映选择性产生巨大影响，从而对这种方法中假定的双自由基中间体的稳定性产生影响。中。此外，虽然对于在均相溶液中进行的反应需要排除氧气，但是当在加气凝胶介质中进行光加成反应时，未观察到收率的下降。