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

A general and efficient procedure for p -toluenesulfonic acid-catalyzed iodination of isoquinolin-1(2 H )-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(2 H )-ones in moderate to good yields, and shows a broad substrate scope and good functional group tolerance.