Thionyl chloride (0.460 mL, 6.321 mmol, 2 eq.) was slowly added to a stirred mixed solution of 2-aminothiazole-4-acetic acid (500 mg, 3.2 mmol) with ethanol (5 mL) at 0 °C. The reaction mixture gradually became clarified, followed by continuous stirring at room temperature for 16 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure to give the crude product. For further purification, two solvent exchanges with ethanol were carried out. The final brown oily product ethyl 2-amino-4-thiazoleacetate was obtained in quantitative yield (588 mg). The product was characterized by NMR hydrogen spectroscopy (400 MHz, DMSO-d6): δ 1.17 (3H, broad peak), 3.72 (2H, broad peak), 4.08 (2H, broad peak), 6.68 (1H, broad peak), 9.43 (2H, broad peak). The resulting compounds can be used directly in the subsequent reaction without further purification.
