139756-22-2

139756-21-1

139756-22-2

Example 1 Preparation of 5-(2-ethoxy-5-chlorosulfonyl)phenyl-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one: Chlorosulfuric acid (50 mL) was added to a 100 mL three-neck flask and placed in an ice bath. Under stirring, 5-(2-ethoxy)phenyl-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one (31.2 g, 0.1 mol) was added in batches. The reaction was exothermic and stirred continuously for 12 hours. Upon completion of the reaction, the reaction solution was slowly poured into ice water (100 g) and a white solid precipitated. The solid was collected by filtration and dried to give a white solid product (30 g) in 76% yield.