Chloroacetone → 7-(2-oxopropoxy)-2H-chromen-2-one

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To a solution of 7-hydroxycoumarin (1.62 g, 10 mmol) in acetone (20 ml) were added potassium carbonate (5.53 g, 40 mmol) and chloroacetone (1.38 g, 15 mmol). The resulting mixture was refluxed for 4 h. (monitored by TLC). Evaporation of the solvent gave a residue which was poured into ice water (50 ml). The resulting solid was collected and crystallized from ethyl acetate to afford 7-(2-oxopropoxy)-2H-1-benzopyran-2-one (3a) (2.10 g, 96.1%) as a white needle crystal. mp: 165°-167° C.; IR(KBr) νmax : 1709, 1620; UV(CHCl3) λmax (log ε): 308 (4.14), 244 (3.52); 1H-NMR (CDCl3): δ2.31 (s, 3H, CH3), 4.65 (s, 2H, OCH2), 6.29 (d, 1H, 3-H), 6.76 (d, 1H, 8-H), 6.88 (dd, 1H, 6-H), 7.42 (d, 1H, 5-H), 7.65 (d, 1H, 4-H). Anal. Calcd for C12H10O4 : C, 66.05; H, 4.62. Found: C, 65.98; H, 4.61.

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