NaH (60% in mineral oil; 53 mg, 1.34 mmol) was added to a solution of cyclopentanol (115 mg, 1.34 mmol) in NMP (3 ml) and the mixture was stirred at room temperature for 15 min. 12-chloro-9-fluoro-5H-6-thia-4,5-diaza-chrysene 6,6-dioxide 503 (150 mg, 0.44 mmol) was added and the mixture was heated at 180 C in a microwave for 2 h. After cooling, the mixture was poured into ice cold water and neutralized using sat aq. KHSO4 solution. The resulting precipitate was collected by filtration and dried. The crude solid was purified by column chromatography with n-hexane/DCM (30:70) as the eluent to give the title compound (23 mg, 20%).
