Visible light-induced denitrogenative annulation reaction of 1,2,3-benzotriazin-4(3 H )-ones with alkenes and alkynes via electron donor–acceptor (EDA) complex formation: a sustainable approach to isoindolinone and isoquinolinone synthesis

An efficient method for the synthesis of isoindolinones and isoquinolinones from 1,2,3-benzotriazin-4(3 H )-ones under visible light is described. The reaction of 1,2,3-benzotriazin-4(3 H )-ones with activated alkenes such as acrylonitrile, vinyl ketone, acrylates and vinyl sulfones in the presence of DIPEA under blue LED light irradiation gave isoindolinones in good to high yields. In a similar manner, the reaction of aromatic terminal alkynes with 1,2,3-benzotriazin-4(3 H )-ones gave 3-substituted isoquinolinones. This method avoids the use of any metal or external photocatalysts and is believed to proceed via electron donor–acceptor (EDA) complex formation facilitated by DIPEA and 1,2,3-benzotriazin-4(3 H )-ones. The practical applicability of these reactions is also demonstrated by performing gram-scale synthesis of isoquinolinones and isoindolinones. Moreover, the utility of this method was showcased through the synthesis of an anxiolytic drug pazinaclone analogue in high yield.