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Under nitrogen, 8.7 g of sodium hydride (99%) dissolved in 600 ml of tetrahydrofuran are cooled to 15° and 75 g of 1,1-diethoxyethylphosphinic acid ethyl ester in 100 ml of tetrahydrofuran are added thereto in the course of 1 hour, the reaction temperature being maintained at less than 25°. The resulting suspension is stirred at room temperature for 2 hours and then a solution of 57.2 g of bromomethylcyclohex-3-ene in 100 ml of anhydrous tetrahydrofuran is added thereto in the course of 30 minutes. The mixture is heated at reflux for 24 hours, then cooled to 0°; 10 ml of water are added and the solvent is removed. The residue is dissolved in dichloromethane, washed twice with water, dried over sodium sulfate, concentrated to dryness by evaporation and distilled. The resulting 1,1-diethoxyethyl-(cyclohex-3-ene)-phosphinic acid ethyl ester is dissolved in 300 ml of dichloromethane that contains 10% by volume ethanol and left to stand at room temperature for 24 hours. Removal of the solvent and distillation yield cyclohex-3-enylmethylphosphinic acid ethyl ester; 31P-NMR (CDCl3):δ=37.1 (s).

1. temperatureare cooled to 15°
2. temperaturein the course of 1 hour, the reaction temperature being maintained at less than 25°
3. customin the course of 30 minutes
4. temperatureThe mixture is heated
5. temperatureat reflux for 24 hours
6. temperaturecooled to 0°
7. customthe solvent is removed
8. dissolutionThe residue is dissolved in dichloromethane
9. washwashed twice with water
10. dry with materialdried over sodium sulfate
11. concentrationconcentrated to dryness by evaporation
12. distillationdistilled
13. dissolutionThe resulting 1,1-diethoxyethyl-(cyclohex-3-ene)-phosphinic acid ethyl ester is dissolved in 300 ml of dichloromethane that
14. waitleft
15. waitto stand at room temperature for 24 hours
16. customRemoval of the solvent and distillation