Synthesis of thieno[2,3-d]pyrimidin-4(3H)-one derivative 2¹⁾
A mixture of 1 (0.3 g, 1.13 mmol), chloroformamidine hydrochloride (0.33 g, 2.83 mmol), and dimethylsulfone (0.53 g, 5.65 mmol) is heated at 130 °C for 30 min. After the mixture is cooled to room temperature, water (10 mL) is added and ammonium hydroxide is used to neutralize the suspension. The solid is filtered off, washed with water, and dried. The crude residue is purified by flash chromatography on silica gel (CH₂Cl₂ /MeOH 10:1) to yield 2 as a white solid (0.28 g, 95%).