Toluene (330 ml) and p-toluenesulfonic acid monohydrate (0.33 g, 1.7 mmol) were heated to reflux in Dean-Stark apparatus under nitrogen for 24 h. The collected water was removed and the Dean-Stark apparatus was replaced with a reflux condenser. 1,2-ethanedithiol (14 ml, 0.167 mol) and 2-bromo-1,1-diethoxyethane (24.5 ml, 0.163 mol) were added and the mixture was heated to reflux for 24 h. The cooled mixture was washed with water (300 ml) and separated. The water layer was back extracted with diethyl ether (3 × 100 ml). The combined organic extracts were washed with brine (3 × 100 ml) and dried twice over anhydrous Na₂SO₄. The solvents were removed in vacuo and the residue was distilled under vacuum (50°C, 4·10^-3 mbar). Yield 6.46 g (34%).

¹H NMR (400 MHz, 298K, CDCl₃) δ_H 6.04 (s, 2H, CH), 3.14 (s, 4H, CH₂)

¹³C NMR (101 MHz, 298K, CDCl3) δ_C 114.39 (CH), 26.30 (CH₂)