To a 250 ml round bottom flask was added 4,4'-thiodiphenol (4.36 g, 20 mmol), O-ethyl S-n-propyl phosphorochloridothioate (9.12 g, 45 mmol), powdered potassium hydroxide (3.37 g, 60 mmol), dicyclohexano-18-crown-6 (catalytic quantity), and acetonitrile. This mixture was refluxed 14 hours, cooled to room temperature, and the organic soluble fraction decanted from the solids. The organic solution was diluted with ether and successively washed with 4M NaOH (3×100 ml), water (2×50 ml), 5% HCl (1×50 ml), water (2×50 ml), and brine (2×50 ml). After drying (MgSO4) the solution was concentrated under reduced pressure to give a colorless oil (4.8 g, 7.6 mmol).
