An oven-dried 100 mL 3-necked flask equipped with a magnetic stirring bar, a reflux condenser carrying a CaCl2 -Drierite drying tube, and a heating mantle, was charged with 4-phenoxyphenol (8.64 g, 46.4 mmol), 4-dimethylaminopyridine (0.57 g, 4.7 mmol), and anhydrous pyridine (40 mL), and the stirred solution was treated slowly with benzenephosphonothioic dichloride (3.6 mL, 23.2 mmol) via syringe. The resulting mixture was stirred at ambient temperature for 64 hours, then was heated at reflux for 1 hour, and allowed to cool. The reaction was monitored periodically by HPLC. Workup consisted of partitioning the reaction mixture between CH2Cl2 (100 mL) and water (100 mL), then washing the organic phase successively with 100 mL portions of 5 percent NaOH, water, 5 percent HCl, water, and saturated brine. Drying (MgSO4) filtration and concentration gave a red oily residue. Purification by chromatography on flash-grade silica gel (4"×2" i.d.), eluting with CH2Cl2 , afforded 9.3 g (79 percent yield) of the title compound as a yellow, viscous oil which had a PDSC (O2) onset/extrap (° C.) of 248/324.
