Photoredox Catalyzed\nTandem Denitrogenative [4 + 2]\nAnnulation of 1,2,3-Benzotriazin-4(3H)-ones with Terminal Olefins

The\ndihydroisoquinolones skeleton is ubiquitous in natural\nproducts\nand biological molecules. Reported strategies for constructing dihydroisoquinolones\nusually require noble metal catalysts or stoichiometric oxidants,\nwhich limit their wide applications. Herein, we developed a photoredox\ncatalyzed tandem denitrogenative [4 + 2] annulation reaction of 1,2,3-benzotriazin-4(3H)-ones\nwith terminal olefins. A variety of dihydroisoquinolones can be accessed\nin moderate to excellent yield. This protocol features high atom-economy,\nmild reaction conditions, and is external oxidant-free, enabling the\nsynthesis of various substituted dihydroisoquinolones.