To two 20 mL microwave reaction tubes were added 1,4-dithio-2,5-diol (2.0 g, 13.1 mmol, 1.0 eq.) and methanol (10.5 mL), respectively, and the reaction tubes were sealed. Methyl cyanoacetate (2.32 mL, 26.3 mmol, 2.0 eq.), triethylamine (1.28 mL, 9.20 mmol, 0.7 eq.), and N,N-dimethylformamide (3 drops) were added sequentially through the septum to each reaction tube. The reaction mixture was placed in a microwave reactor and the reaction was heated at 50 °C for 3 min. Upon completion of the reaction, the reaction solutions in the two tubes were combined and left at room temperature to allow the product to precipitate. The precipitate was collected by filtration and washed with cold methanol to afford methyl 2-aminothiophene-3-carboxylate (16as) as a white solid (3.88 g, 24.7 mmol, 94% yield).
