Step 1: Ethyl chloroformate (~1.5 eq.) was added slowly and dropwise to a solution of acetone (80 mL) containing 3-methoxycinnamic acid (11.0 g, 62 mmol) and triethylamine (12.5 g, 124 mmol) at 0 °C. After maintaining the reaction at this temperature for 1 hour, aqueous NaN3 (6.40 g, 100 mmol dissolved in 35 mL H2O) was added dropwise and the reaction mixture was stirred at room temperature for 16 hours. Upon completion of the reaction, water (100 mL) was added and volatiles were removed under vacuum. The reaction mixture was extracted with toluene (3 x 50 mL) and the organic layers were combined, dried with MgSO4 and filtered. The filtrate was slowly added dropwise to a preheated mixture of diphenylmethane (50 mL) and tributylamine (30 mL), and toluene was removed by distillation during the dropwise addition. After the dropwise addition, the reaction temperature was raised to 210 °C and maintained for 2 hours. At the end of the reaction, the mixture was cooled, the precipitated product was collected by filtration, washed with hexane (2 x 50 mL) and dried to give 6-methoxyisoquinolin-1(2H)-one as a white solid (5.53 g, 51% yield) (Ref. Nicolas Briet et al., Tetrahedron, 2002, 5761-5766).LC-MS Analysis showed MS m/z 176 (M++H).
