The general procedure for the synthesis of diphenylphosphinic acid hydroxylamine from diphenylphosphinic acid chloride is as follows: to a 5 L four-necked round-bottomed flask (RBF) equipped with an overhead stirrer and a thermocouple are added sequentially (1) a solution of 60.85 grams (1.52 moles, 2.4 eq.) of NaOH dissolved in 180 mL of water, (2) 110.12 grams (1.58 moles, 2.5 eq.) of hydroxylamine- HCl dissolved in a solution of 180 mL of water, and (3) 180 mL of dioxane. The mixture was cooled to 0°C in an ice/acetone bath. Subsequently, 150 g of ice was added and a solution of diphenylphosphinic chloride (150.0 g, 0.634 mol, 1 eq.) dissolved in 180 mL of dioxane pre-cooled to about 10°C was added all at once. During the reaction the mixture becomes very viscous with the formation of a white precipitate and vigorous stirring is required. The internal temperature of the reaction rises to 22°C. After continued stirring for 5 to 10 minutes, the reaction mixture was diluted with 2.5 L of ice water and filtered through a large 15 cm diameter sintered funnel. The filter cake was drained on a glass stock for 1 hour, after which it was transferred back into 5 L of RBF. The solid was suspended in 500 mL of ice-cold 0.25 N NaOH solution with vigorous stirring for 5 to 10 min, filtered again, and washed twice with ice water, followed by drying on a porous filter overnight. The partially dried product was dried in a vacuum oven (50 °C, 0.1 Torr) for 12 h, after which it was well pulverized using a mortar and pestle grinder. Finally, the product was dried in a vacuum oven for another 16 hours to give 122 g (82% yield) of the target product diphenylphosphinoylhydroxylamine as a white powder.
