Recent years have witnessed a continuous development of photocatalysts to satisfy the growing demand of photophysical and redox properties in photoredox catalysis, with complex structures or alternative strategies devised to access highly reducing or oxidising systems. We report herein the use of peri‐xanthenoxanthene (PXX), a simple and inexpensive dye, as an efficient photocatalyst. Its highly reducing excited state allows activation of a wide range of substrates, thus triggering useful radical reactions. Benchmark transformations such as the addition of organic radicals, generated by photoreduction of organic halides, to radical traps are initially demonstrated. More complex dual catalytic manifolds are also shown to be accessible: the β‐arylation of cyclic ketones is successful when using a secondary amine as organocatalyst, while cross‐coupling reactions of aryl halides with amines and thiols are obtained when using a Ni co‐catalyst. Application to the efficient two‐step synthesis of the expensive fluoro‐tetrahydro‐1H‐pyrido[4,3‐b]indole, a crucial synthetic intermediate for the investigational drug setipiprant, has been also demonstrated.
The front cover picture illustrates the photophysical and practical properties of PXX (peri‐xanthenoxanthene) as novel photocatalyst. A synthetic experiment is portrayed as a video game where you need to choose the right components to start your game: PXX has now been unlocked as a photocatalyst with high reducing power, moderate oxidizing power, high versatility and low cost. In this work, Bonifazi and co‐workers demonstrate the use of PXX in a variety of synthetic transformations, from radical additions, to organocatalytic reactions, to nickel‐catalysed cross couplings. Details can be found in the Research Article by Bonifazi and co‐workers (C. Pezzetta, A. Folli, O. Matuszewska, D. Murphy, R. W. M. Davidson, D. Bonifazi, Adv. Synth. Catal. 2021, 363, 4740‐4753; DOI: 10.1002/adsc.202100030)
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