Photocatalytic Cascade Cyclization of Unactivated Alkenes With N ‐Aminopyridinium Salts Toward Tetrahydropyridazine and Dihydropyrazole Derivatives

ABSTRACT A visible light–induced cascade cyclization strategy of unactivated alkenes with N ‐aminopyridinium salts was explored to build a series of tetrahydropyridazines and dihydropyrazoles in yield of 17% –82% with 41 examples. This protocol features mild reaction conditions (irradiation with a 10 W blue LED at room temperature) and can simultaneously form two chemical bonds, offering a rapid and concise approach to five‐ or six‐membered heterocyclic frameworks. The scalability of this method and the feasibility of further transformations have also been demonstrated, highlighting its potential for applications in the industrial and pharmaceutical sectors.