Sulphone Coupling

Abstract

A dry, 1-litre, four-necked flask, equipped with a mechanical stirrer, a thermometer, a pressure equalizing dropping funnel and a condenser, is flushed with N₂. To the flask are added 136.8 g sodium benzenesulphinate (0.834 mol), 178 ml H₂0 and 213 ml glacial acetic acid. In the dropping funnel is placed vinyl-β-ionol (2) (100 g, 0.417 mol) (see Example 2). The reaction mixture is stirred at 60°C under N₂. The vinyl-β-ionol (2) is added over 1 h; then additional 25 ml acetic acid is added through the funnel and stirring is continued for 4 h at 62°C. After cooling to 40-45°C and addition of 210 ml hexane, the mixture is poured into a 1-litre separatory funnel. The aqueous layer is separated and extracted with 40 ml hexane. To the hexane extracts, 39 ml H₂0 and enough NaOH Solution (48% w/w) are added to bring the pH of the aqueous layer to 8–9 in 15 min. The mixture is then poured into a separatory funnel, the aqueous layer is separated and the hexane layer is washed with 40 ml H₂0. After drying with Na₂SO₄, the hexane layer is evaporated at 40–45°C (bath temperature) as the pressure is gradually lowered from 10–25 to 0.1–0.2 mm Hg, to give 148 g (93%) of crude C₁₅-sulphone 1[(9E):(9Z)=88:12]. For the purification, a 1-litre, three-necked flask is fitted with a mechanical stirrer, a thermometer and a condenser. The 300 ml hexane and 100 g of the crude C₁₅-sulphone 1 are stirred at 25–30°C until dissolution is complete. The temperature is lowered and held at 10–15°C with stirring for 4 h. After standing overnight at 0–5°C, the mixture is filtered on sintered glass No 3. The crystals are washed with 100 ml of hexane and dried under high vacuum to give 60 g (60% referred to the crude product) of pure (9E)-C₁₅-sulphone 1 (m.p. 57–58°C) [1].