[Br:1][C:2]1[CH:3]=[C:4]([CH:8]=[C:9]([Br:12])[C:10]=1[OH:11])[C:5]([OH:7])=O.S(Cl)(Cl)=O.[NH:17]1[CH2:22][CH2:21][O:20][C:19]2[N:23]=[CH:24][CH:25]=[CH:26][C:18]1=2.O>CN(C)C(=O)C>[Br:12][C:9]1[CH:8]=[C:4]([C:5]([N:17]2[CH2:22][CH2:21][O:20][C:19]3[N:23]=[CH:24][CH:25]=[CH:26][C:18]2=3)=[O:7])[CH:3]=[C:2]([Br:1])[C:10]=1[OH:11]
3,5-dibromo-4-hydroxy-benzoic acid (65 mg, 0.22 mmol) was dissolved in N,N-dimethyl acetamide (1.5 ml) and then cooled to −5□. Thionyl chloride (0.024 ml, 0.33 mmol) was added thereto and stirred at −5□ for 30 minutes. 2,3-dihydro-1H-pyrido[2,3-b][1,4]oxazine dissolved in N,N-dimethyl acetamide (0.7 ml) was added thereto and then stirred at −5□ for 20 minutes, and subsequently stirred at room temperature for 15 hours. Water was added and the mixture was extracted with dichloromethane, and then the (extracted) combined organic layer was dried over anhydrous sodium sulfate (Na2SO4), filtered and evaporated under reduced pressure. The residue was purified by column chromatography on silica eluting with a solvent of n-hexane:ethyl acetate=1:1. The fractions containing the product were collected and evaporated to obtain pale-yellow solid (28 mg, 31%).
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