[Synthesis]
Step 2: Synthesis of 2-(methylthio)-7,8-dihydroquinazolin-5(6H)-one. To a solution of 2-[(dimethylamino)methylene]-1,3-cyclohexanedione (0.5 g, 2.9 mmol) in N,N-dimethylformamide (DMF, 2 mL) was added sodium acetate (0.39 g, 4.7 mmol) and 2-methyl-2-isothiourea (0.9 g, 3.5 mmol). The reaction mixture was heated at 100 °C with stirring for 5 hours. After completion of the reaction, the mixture was diluted with dichloromethane (30 mL), the organic layer was separated and washed with deionized water (2 x 30 mL). Subsequently, the solvent was evaporated under reduced pressure and the residue was dissolved in ethyl acetate (EtOAc, 50 mL) and washed again with deionized water (2 × 30 mL). The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford the target product 2-(methylthio)-7,8-dihydroquinazolin-5(6H)-one (0.5 g, 86% yield) as a solid.1H NMR (CDCl3, 400 MHz): δ 8.94 (s, 1H), 3.01 (t, J = 6 Hz, 2H), 2.64 (t, J = 6.0 Hz, 2H), 2.58 (t, J = 6.0 Hz, 2H), 2.60 (t, J = 6.0 Hz, 2H), 2.60 (t, J = 6.0 Hz, 2H). 2H), 2.58 (s, 3H), 2.14 (quintuple peak, J = 6.2 Hz, 2H); LCMS [M + H]+: 195. |