[CH2:1]1[C:10]2[C:5](=[CH:6][CH:7]=[CH:8][CH:9]=2)[CH2:4][CH2:3][NH:2]1.Br[CH2:12][C:13]([O:15][CH2:16][CH3:17])=[O:14].C([O-])([O-])=O.[Cs+].[Cs+]>CN(C)C=O>[CH2:16]([O:15][C:13](=[O:14])[CH2:12][N:2]1[CH2:3][CH2:4][C:5]2[C:10](=[CH:9][CH:8]=[CH:7][CH:6]=2)[CH2:1]1)[CH3:17]To a solution of 1,2,3,4-tetra-hydroisoquinoline (2.664 g, 20 mmol) and ethyl bromoacetate (3.647 g, 22 mmol) in N,N-dimethylformamide (23 mL), was added Cs2CO3 (7.168 g, 22 mmol) under N2. The mixture was stirred at room temperature for 4 hours. The solvent was removed under reduced pressure, and the remaining residue was subjected to silica gel chromatography, eluting with ethyl acetate/hexanes (33:66) to afford Intermediate 199(a) (3.39 g, 15.5 mmol) as yellow oil in 77% yield.
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