Synthesis of 3,4-Dihydro-5-hydroxy-1(2H)-isoquinolinone

3,4-Dihydro-5-hydroxy-1(2H)-isoquinolinone(1) was synthesized from isoquinoline(2) by a three-step reaction that isoquinoline5-sulfonic acid(3) was prepared by the reaction of fuming sulfuric acid with 2,1,5-dihydroxy-isoquinoline(4) was obtained from 3 in a melted mixture of sodium hydroxide and potassium hydroxide and hydrogenation of 4 to 1 was fulfilled in the presence of 5% PdC.The overall yield of 1 was 47.6%.The structure of 1 was identified by ~1H NMR and MS.