Department of Colloid Chemistry, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476, Potsdam, Germany.
Angew Chem Int Ed Engl. 2017 Aug 1;56(32):9336-9340. doi: 10.1002/anie.201703438. Epub 2017 Jul 6.
Photocatalytic Diels-Alder (D-A) reactions with electron rich olefins are realized by graphitic carbon nitride (g-C N ) under visible-light irradiation and aerobic conditions. This heterogeneous photoredox reaction system is highly efficient, and the apparent quantum yield reaches a remarkable value of 47 % for the model reaction. Dioxygen plays a critical role as electron mediator, which is distinct from the previous reports in the homogeneous Ru complex photoredox system. Moreover, the reaction intermediate vinylcyclobutane is captured and monitored during the reaction, serving as a direct evidence for the proposed reaction mechanism. The cycloaddition process is thereby determined to be the combination of direct [4+2] cycloaddition and [2+2] cycloaddition followed by photocatalytic rearrangement of the vinylcyclobutane intermediate.
在可见光照射和有氧条件下，石墨相氮化碳（g-C N ）实现了与富电子烯烃的光催化 Diels-Alder（D-A）反应。该非均相光氧化还原反应体系具有高效性，对于模型反应，表观量子产率达到了显著的 47%。氧气作为电子介体发挥了关键作用，这与之前在均相 Ru 配合物光氧化还原体系中的报道明显不同。此外，在反应过程中捕获并监测到反应中间体乙烯基环丁烷，这为提出的反应机制提供了直接证据。因此，环加成过程被确定为直接[4+2]环加成和[2+2]环加成的组合，随后是乙烯基环丁烷中间体的光催化重排。
