A solution of the crude 1- (2, 2-diethoxyethylsulfanyl)-3-methoxybenzene (8.27 g, 32.3 mmol) in hexane (100 ml) was added dropwise to a solution of methanesulfonic acid (1.05 mL, 1.55 g, 16.1 mmol) in hexane (1000 mL) containing 16.5 g of celite (2 wt. eq.). The resultant solution was heated at reflux for 1 hour. After cooling to room temperature, the reaction was quenched by the addition of Et3N (4.5 ml, 3.26 g, 32.3 mmol. The crude reaction mixture was filtered and then concentrated in vacuo. 6-Methoxybenzo(b)thiophene was obtained after purification.
