677304-83-5

677304-90-4

677304-83-5

The general procedure for the synthesis of 7-carboxybenzothiazole from ethyl benzo[d]thiazole-7-carboxylate was as follows: an aqueous sodium hydroxide solution (50%, 10 mL) was slowly added to a mixture of methanol (65 mL) and tetrahydrofuran (20 mL) containing ethyl 1,3-benzothiazole-7-carboxylate (3.5 g, 16.89 mmol) at 0 °C, followed by water ( 5 mL). The reaction mixture was stirred at room temperature for 4 hours. Upon completion of the reaction, the volatile solvent was removed by distillation under reduced pressure. The residue was dissolved in water (100 mL) and the pH of the solution was adjusted with concentrated hydrochloric acid to 5. The mixture was cooled to 0 °C and maintained for 30 min to promote product precipitation. The solid product was collected by filtration and washed with cold water (10 mL). Finally, the product was dried in a vacuum oven at 70 °C overnight to afford 2.75 g (91% yield) of the target compound 7-carboxybenzothiazole. The product was characterized by 1H NMR (500 MHz, DMSO-d6): δ 7.71 (t, J=7.5 Hz, 1H), 8.15 (d, J=7 Hz, 1H), 8.38 (d, J=8 Hz, 1H), 9.51 (s, 1H), 13.74 (bs, 1H); the mass spectrometry (APCI) showed m/z 178 (M+-1).