Indole alkaloids represent an important class of molecules, with many naturally occurring derivatives possessing significant biological activity. One area that requires further development in the synthesis of indole derivatives is the Diels–Alder reaction. In this work, we expand on our previously developed heterogeneous protocol for the [4 + 2] cycloaddition of indoles and electron-rich dienes mediated by platinum nanoparticles supported on titanium dioxide semiconductor particles (Pt(0.2%)@TiO₂) with visible-light irradiation. This reaction proceeds with broad scope and is more efficient per incident photon than the previous homogeneous method, and the catalyst can be easily recycled and reused.

中文翻译：

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异质铂修饰的二氧化钛介导的光催化吲哚Diels-Alder环加成反应

吲哚生物碱代表一类重要的分子，许多天然衍生物具有重要的生物活性。Diels-Alder反应是需要进一步发展吲哚衍生物合成的领域。在这项工作中，我们扩展了先前开发的异构协议，该协议用于吲哚和富电子二烯的[4 + 2]环加成反应，该吲哚和富电子二烯由载于二氧化钛半导体颗粒（Pt(0.2%)@TiO ₂）上的铂纳米颗粒介导，且可见-光照射。该反应进行的范围很广，并且每个入射光子的反应比以前的均相方法更有效，并且催化剂易于回收和再利用。