Design and Application of Novel, Visible-Light Acridinium-type Organophotocatalysts

本项目致力于设计新型吖啶基结构作为有机光催化剂，在其存在状态下改善氧化和催化性能，以开发有价值的氧化光催化。可见光光氧化还原催化已经成为一种强大的合成工具，提供了获得独特反应的途径。除过渡金属光敏剂外，有机染料作为光氧化还原催化剂也受到了广泛的关注，其中吖啶盐是最强大的有机光催化型氧化剂之一。然而，它们固有的不稳定性和合成的可及性限制了它们的结构为c9 -芳基取代物。本项目将开发含c9 -酰胺和酰胺等构杂环的吖啶盐的新合成方法，包括新的氧化C-H功能化方法。我们最近证明了相关的c9 -亚胺吖啶盐比标准的c9 -甲酰基吖啶盐具有更强的光活性。然而，它们的替代模式受到限制，因此所提出的方法和结构将克服当前的可调谐性问题。该项目还旨在更好地了解所提出的新催化剂的光物理性质和性能，以确定改进的高活性结构。获得的信息将用于重新设计新的催化剂，其活性将在具有挑战性的可见光催化反应中进行评估，例如迄今为止仍然要求很高的烯烃底物的加氢功能化，涉及C(sp2)-Si键的脱苯偶联反应或选择性自由基环化有价值的杂环。

This project focusses on the design of novel acridinium-based structures as organophotocatalysts with improved oxidative and catalytic properties in their exited state for the development of valuable oxidative photocatalysis. Visible light photoredox catalysis has arisen as a powerful synthetic tool, offering access to unique reactivities. Besides transition-metal photosensitizers, organic dyes have recently been attracted great attention as photoredox catalysts, from which acridinium salts shine as one of the most powerful organophotocatalyst-type oxidants. However, their intrinsic instability and synthetic accessibility limit the structures to C9-aryl substituted species. In this project, new synthetic methods, including novel oxidative C-H functionalization approaches, to acridinium salts bearing C9-amide and amide-isosteric heterocycles will be developed. We have recently demonstrated that related C9-imide acridinium salts present enhanced photoactivities than standard C9-mesityl acridinium salts. However, their substitution pattern is constrained for which the proposed methods and structures will overcome the current tuneability issues. This project also aims at a better understanding of the photophysical properties and performance of the proposed new catalysts in order to identify improved highly active structures. The information obtained will be used to re-design new catalysts, whose activity will be evaluated in challenging visible light photocatalytic reactions, such as hydrofunctionalization of to date still highly demanding olefinic substrates, desilylative coupling reactions involving C(sp2)-Si bonds or selective radical cyclizations towards valuable heterocycles.