[CH2:1]([C:8]1[C:13](=[O:14])[N:12]2[CH:15]=[CH:16][CH:17]=[CH:18][C:11]2=[N:10][C:9]=1[CH:19]=[O:20])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH:21]([Mg]Br)=[CH2:22]>C1COCC1>[CH2:1]([C:8]1[C:13](=[O:14])[N:12]2[CH2:15][CH2:16][CH2:17][CH2:18][C:11]2=[N:10][C:9]=1[CH:19]([OH:20])[CH:21]=[CH2:22])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1A mixture of 2.5 g (9.5 mmol) of the product from Step 6 (16) in 35 mL THF was cooled to −78° C. To the resulting solution was added dropwise 11.4 mL (11.4 mmol) of vinyl magnesium bromide and stirred at −78° C. for 3 hours. The reaction was quenched with saturated NH4Cl and extracted with ethyl acetate (4×). The combined organic layers were dried over MgSO4 and the solvent was removed in vacuo yielding 2.95 g of 3-benzyl-2-(1-hydroxyprop-2-enyl)-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one (23) as a yellow oil.
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