Cross‐dehydrogenative Coupling of N‐Aryl Tetrahydroisoquinolines Catalyzed by an Anthraquinone‐containing Polymeric Photosensitizer

This work reports the photocatalytic application of an anthraquinone‐containing polymeric photosensitizer (AQ‐PHEMA) in the visible light‐induced cross‐dehydrogenative‐coupling of N‐aryl tetrahydroisoquinolines with several nucleophiles, including nitromethane, 1‐methyl‐2‐alkyl ketone and dialkyl (aryl) phosphine oxide. The results revealed that the reaction could be catalyzed by AQ‐PHEMA efficiently to afford a series of 1‐substituted‐2‐aryl‐1,2,3,4‐tetrahydroisoquinolines in good to excellent yields with nice substrate tolerance under aerobic conditions at room temperature. The practical application potential was also showcased by a gram‐scale synthesis. More importantly, the utilization of AQ‐PHEMA as a heterogeneous photosensitizer also showed nice recyclability and reusability of the catalyst, whereas AQ‐PHEMA can be easily separated and reused for at least 8 times without significant loss of photocatalytic activity. An anthraquinone‐containing polymeric photosensitizer (AQ‐PHEMA) can catalyze the cross‐dehydrogenative‐coupling of N‐aryl tetrahydroisoquinolines with several nucleophiles (nitromethane, 1‐methyl‐2‐alkyl ketone and dialkyl (aryl) phosphine oxide) efficiently by visible light to afford a series of 1‐substituted‐2‐aryl‐1,2,3,4‐tetrahydroisoquinolines in good to excellent yields with nice substrate tolerance.