77893-68-6

17249-80-8

77893-68-6

General procedure for the synthesis of 2-bromo-3-chlorothiophene (compound 28-1) from 3-chlorothiophene: N-bromosuccinimide (NBS, 9.80 g, 55 mmol) was added to a mixture of chloroform (30 mL) and acetic acid (30 mL) of 3-chlorothiophene (6.52 g, 55 mmol). The reaction mixture was heated under reflux conditions for 1.5 h and subsequently cooled to room temperature. After addition of water (70 mL), the mixture was extracted with chloroform (30 mL x 2). The organic layers were combined and washed sequentially with saturated sodium bicarbonate solution (40 mL) and brine (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated to give the brown oily material 28-1 (10.02 g, quantitative yield), which was used directly in the subsequent reaction without further purification.