CS(O)(=O)=O.O=[C:7]1[N:12]([C:13]2[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=2)N=[C:10](CCC(OCC)=O)[CH2:9][CH2:8]1.[OH-:26].[Na+].[CH2:28]([OH:31])[CH2:29][CH3:30]>>[O:31]=[C:28]([O:31][CH2:28][CH2:29][CH3:30])[CH2:29][C:30]1[C:14]2[C:13](=[CH:18][CH:17]=[CH:16][CH:15]=2)[NH:12][C:7]=1[CH2:8][CH2:9][C:10]([O:31][CH2:28][CH2:29][CH3:30])=[O:26]Methanesulfonic acid (1.15 equiv.) was added to a stirred solution of ethyl 3-(6-oxo-1-phenyl-1,4,5,6-tetrahydropyridazin-3-yl)propanoate from Step 1 in n-propanol (1.1 M). The mixture was stirred overnight at 80° C. The mixture was cooled to rt and neutralized with aqueous 1 N NaOH (1 equiv.). Final mixture was concentrated under vacuum, diluted with toluene and concentrated again. The residue was purified by column chromatography on silica gel using a CombiFlashRF (Teledyne ISCO) eluting with EtOAc/Hex (0:100 to 60:40) to give the title compound (79%) as a brown oil.
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