At -5°C to 0°C, under nitrogen atmosphere, diisopropyl phosphite (4 mL, 24 mmol) was added dropwise to a suspension of NaH (28.8 mmol, 1.2 equivalents) in dry THF (25 mL). The mixture was then stirred at 20°C for 3 h, and carbon disulfide (9.6 mmol, 0.4 equivalents) was added dropwise. The reaction mixture turned brown. Stirring was continued for 3 h, and the mixture was then poured into a saturated solution of NH4Cl and extracted with Et2O.
The combined organic layers were dried (MgSO4), the solvent was removed under reduced pressure, and the product was purified by vacuum distillation (110-115 °C at 3.10-2 mbar) to give the compound Tetraisopropyl methylenediphosphonate, a pale yellow oil (52%).
