ClC([O:4][CH2:5]C)=O.[CH2:7]([O:9][C:10]1[CH:11]=[C:12]([CH:18]=[CH:19][CH:20]=1)[CH:13]=[CH:14]C(O)=O)[CH3:8].C([N:23](CC)CC)C.[N-]=[N+]=[N-].[Na+].C1(CC2C=CC=CC=2)C=CC=CC=1.C(N(CCCC)CCCC)CCC>CC(C)=O.O>[CH2:7]([O:9][C:10]1[CH:11]=[C:12]2[C:18](=[CH:19][CH:20]=1)[C:5](=[O:4])[NH:23][CH:14]=[CH:13]2)[CH3:8]Ethyl chloroformate (4.3 mL, 44.5 mmol) was added drop wise at 0° C. to a solution of 3-ethoxycinnamic acid (5.71 g, 29.7 mmol) and triethylamine (8.3 mL, 59.4 mmol) in acetone (35 mL). After 1 hour at 0° C., aqueous sodium azide (3.1 g, 47.5 mmol, 16 mL water) was added dropwise and the reaction mixture was stirred at 23° C. for 16 hours. Water (50 mL) was added to the mixture and the volatile was removed under vacuo. The resulting slurry was extracted with toluene (3×25 mL) and the combined organic layers were dried (MgSO4). The dried solution was filtered and added dropwise at 190° C. to a solution of diphenylmethane (25 mL) and tributylamine (14.2 mL, 59.4 mmol). The toluene was distilled off as added. After complete addition, the reaction temperature was raised to 210° C. for 2 h. After cooling, the precipitated product was collected by filtration and washed with hexanes and dried under vacuum to yield 6-ethoxy-2H-isoquinolin-1-one (1.92 g, 10.2 mmol, 34% yield). MS m/z 190 (M++H).
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