Pentaerythritol → Pentaerythritol, cyclic phosphate (1:1) (8CI)

In a 250 mL four-necked reaction flask fitted with a mechanical stirrer, pot thermometer, addition funnel, and condenser with gas outlet were placed 42.5 g (0.313 mole) of pentaerythritol and 150 mL of PHOSFLEX 41P brand of isopropylated triphenyl phosphate under nitrogen. The mixture was stirred and heated at 95° C. as 49.2 g (0.321 mole) of phosphorus oxychloride was added dropwise over five hours. The resulting white slurry was heated to 100° C. with a nitrogen gas sparge for eight hours to remove HCl. The mixture was cooled to 50° C. and filtered. The solid was washed three times with 40 mL of hexane and dried at 100° C./2 mm Hg for sixteen hours to give 42.3 g (71.2% yield) of crude pentaerythritol phosphate alcohol (2,6,7-trioxa- 1-phosphabicyclo [2.2.2]octane-4-methanol-1-oxide). The product had a 31P NMR resonance at -6.0 ppm in d6 -DMSO.