Visible‐Light‐Induced Controlled Oxidation of N ‐Substituted 1,2,3,4‐Tetrahydroisoquinolines for the Synthesis of 3,4‐Dihydroisoquinolin‐1(2 H )‐ones and Isoquinolin‐1(2 H )‐ones

A visible light‐rose bengal‐TBHP mediated, controlled oxidation of N ‐substituted 1,2,3,4‐tetrahydroisoquinolines is developed for the synthesis of 3,4‐dihydroisoquinolin‐1(2 H )‐ones and isoquinolin‐1(2 H )‐ones. The present method feature's a broad substrate scope, good functional group tolerances, and the products were prepared in good to excellent yields. The developed methodology further demonstrated in the synthesis of isoindolo[2,1‐b] isoquinolin‐5(7 H )‐one (topoisomerase‐I inhibitor).