To a stirred solution of the isoquinoline from step A (1.17 g, 3.0 mmol) in anhydrous DMSO (12 mL) was added sodium nitrite (1.24 g, 18 mmol). To the mixture was added slowly over 30 min a solution of acetic anhydride (1.84 g, 18 mmol) in anhydrous DMSO (12 mL). The mixture was stirred overnight and TLC showed most starting material remained. More sodium nitrite (1.24 g, 18 mmol) and acetic anhydride (1.84 g, 18 mmol) in anhydrous DMSO (12 mL) was added and stirring was continued for about 1 h. During this period yellow solid precipitated and TLC showed a new product at Rf 0.5 (hexane/EtOAc 1:1). The mixture was poured into a saturated aqueous solution of sodium bicarbonate (100 mL) and extracted with EtOAc (100 mL×2). Chromatography on silica eluting with 20% EtOAc/Hexane gave an oil. (0.81 g, 62%). LCMS (+APCI) m/z 454 (M+H+NH3).
