p-Toluenesulfonic acid-catalyzed regioselective C4-H iodination of isoquinolin-1(2H)-ones

A general and efficient procedure for p-toluenesulfonic acid-catalyzed iodination of isoquinolin-1(2H)-ones with N-iodosuccinimide at room temperature is described. This method provides an alternative way of constructing C-I bonds, affords various 4-iodoisoquinolin-1(2H)-ones in moderate to good yields, and shows a broad substrate scope and good functional group tolerance.