C([O:3][C:4]([C:6]1[N:15]=[C:14](Cl)[C:13]2[C:8](=[CH:9][CH:10]=[C:11]([O:17]C)[CH:12]=2)[N:7]=1)=[O:5])C.[CH2:19]([S-:21])[CH3:20].[Na+].O.C(O)(=O)CC(CC(O)=O)(C(O)=O)O>CN(C=O)C.CCOC(C)=O>[CH2:19]([S:21][C:14]1[C:13]2[C:8](=[CH:9][CH:10]=[C:11]([OH:17])[CH:12]=2)[N:7]=[C:6]([C:4]([OH:3])=[O:5])[N:15]=1)[CH3:20]
To a solution of 4-chloro-6-methoxy-quinazoline-2-carboxylic acid ethyl ester (1.22 g, 4.574 mmol) in anhydrous DMF (4.0 mL) was added sodium ethanethiolate (3.07 g, 36.59 mmol) and the reaction mixture was heated at 140° C. for 3 h. Water and EtOAc was added . The pH of the aq. layer was adjusted to 6 with citric acid. The organic layer was separated and the aq. layer was extracted with EtOAc. The combined organic layer was washed with water, brine, dried (Na2SO4) and concentrated under reduced pressure to give 0.770 g of 4-ethylsulfanyl-6-hydroxy-quinazoline-2-carboxylic acid.
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