Nickel-Catalyzed Denitrogenative Annulation Reactions of 1,2,3-Benzotriazin-4(3H)-ones with 1,3-Dienes and Alkenes

1,2,3-Benzotriazin-4(3H)-ones react with 1,3-dienes in the presence of a nickel(0)/phosphine complex to give a variety of 3,4-dihydroisoquinolin-1(2H)-ones. Oxidative insertion of nickel(0) into the triazinone moiety prompts extrusion of dinitrogen to give a five-membered ring azanickelacyclic intermediate. Subsequent insertion of 1,3-dienes into the nickel-carbon bond followed by allylic amidation affords 3,4-dihydroisoquinolin-1(2H)-ones. Alkenes also undergo insertion into the five-membered ring azanickelacyclic intermediate, and subsequent reductive elimination gives 3-substituted 3,4-dihydroisoquinolin-1(2H)-ones.