At room temperature tert.-butyl 2,2,2-trichloroacetimidate (437 mg, 0.36 mL, 2.0 mmol) was added to a solution of 2-[1-(3,4-dimethoxy-benzyl)-7-hydroxy-6-methoxy-3,4-dihydro-1H-isoquinolin-2-yl]-N-benzyl-acetamide (95.3 mg, 0.2 mmol) in dichloromethane (5.0 mL) and cyclohexane (5.0 mL). The reaction mixture was treated with a solution of boron trifluoride diethyl etherate (50 μL, 0.4 mmol) in 10 mL dichloromethane and stirred for 22 h. Another portion of tert.-butyl 2,2,2-trichloroacetimidate (244 mg, 0.20 mL, 1.1 mmol) was added. After stirring for three days a saturated solution of NaHCO3 (10 mL), water (10 mL) and ethyl acetate (40 mL) were added, the phases were separated and the aqueous phase was extracted three times with ethyl acetate (30 mL). The combined organic phases were concentrated in vacuo and purified by flash-chromatography to give the titled product (80.4 mg, 75%) as pale yellow oil.
