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0 °C

Under nitrogen atmosphere, to a mixture of magnesium (3.2 g) and a piece of iodine in diethylether (20 ml) was dropwise added to a solution of 1,5-dibromopentane (13.21 g) and 1,2-dibromoethane (1.21 ml) in diethylether (80 ml) at 40° C. for 1 hour. The mixture was refluxed for 1 hour, cooled to room temperature and allowed to stand for 2 hours. The upper layer of diethylether was removed through cannula, to obtain the di-Grignard reagent, which was dissolved in dichloromethane (250 ml). The resulting di-Grignard reagent as it is was used for the following reaction. To benzylphosphonic acid (10.0 g) was added thionyl chloride (30 ml) and then a drop of DMF, and the mixture was refluxed for 3 hours and concentrated under reduced pressure. The residue was dissolved in dichloromethane (210 ml), and the mixture was cooled to 0° C. To the mixture was dropwise added a solution of the above di-Grignard reagent in dichloromethane, which was cooled to 0° C., through cannula for 1 hour, and the mixture was stirred at room temperature for 20 hours. To the reaction mixture were added 10% ammonium chloride solution (100 ml) and saturated sodium chloride solution, and the mixture was extracted with dichloromethane. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was separated and purified with column chromatography (ethanol/ethyl acetate=1:3→1:2) to give 1-benzylphosphorinane-1-oxide (5.39 g) as colorless crystals.

1. concentrationconcentrated under reduced pressure
2. dissolutionThe residue was dissolved in dichloromethane (210 ml)
3. additionTo the mixture was dropwise added a solution of the above di-Grignard reagent in dichloromethane, which
4. temperaturewas cooled to 0° C., through cannula for 1 hour
5. additionTo the reaction mixture were added 10% ammonium chloride solution (100 ml) and saturated sodium chloride solution
6. extractionthe mixture was extracted with dichloromethane
7. washThe organic layer was washed with saturated sodium chloride solution
8. dry with materialdried with magnesium sulfate
9. concentrationconcentrated under reduced pressure
10. customThe residue was separated
11. custompurified with column chromatography (ethanol/ethyl acetate=1:3→1:2)