A mixture of 3-(methylamino)-5-(1H-pyrazol-4-yl)thiophene-2-carboxamide dihydrochloride (145 mg, 0.491 mmol), saturated aqueous NaHCO3 (50 mL) and EtOAc (50 mL) was shaken well. The organic layer was collected, dried over MgSO4, filtered and concentrated under reduced pressure. This residue was mixed with cyclopentanone (2.00 mL, 22.6 mmol), PTSA (9.34 mg, 0.049 mmol), MgSO4 (118 mg, 0.982 mmol) and DMF (2 mL). This mixture was stirred at 80° C. overnight. The mixture was poured into saturated aqueous NaHCO3 and extracted with 3:1 EtOAc/THF (100 mL), and the extract was dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by column chromatography (Purif, silica gel, 95:5 hexane/EtOAc to EtOAc then to 90:10 EtOAc/MeOH) to afford a yellow solid. This solid was triturated with EtOAc, and the precipitate was collected by filtration to afford the title compound (75.4 mg, 53%) as a yellow solid:
