Sodium Hydroxide → Silver 2,2-difluoro-4-pentenoate

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Reaction Steps

A suspension of silver oxide in water is prepared by adding a solution of NaOH (1.76 g, 0.044 mol) in water (100 ml) to an aqueous solution of silver nitrate (7.14 g, 0.042 mol in 100 ml), decanting the supernatant liquid, washing the residue with water (3×100 ml) and adding 100 ml of water. To this vigorously stirred suspension is added a solution of 2,2-difluoro-4-pentenoic acid (III) (5.44 g, 0.04 mol) in water (100 ml). After 10 minutes the mixture is filtered and the filtrate concentrated (20 Torr, 30° C.) to afford a solid residue which is dried over phosphorus pentoxide (0.05 Torr, 50° C., 24 hours) to give 8.4 g (87%) of silver 2,2-difluoro-4-pentenoate as a white amorphous powder. A suspension of 7.3 g (0.03 mol) of the silver salt in 50 ml of dichloromethane is stirred under nitrogen, cooled to 0° C. and then 1.9 g (1.3 ml, 0.015 mol) of oxalyl chloride is added slowly. The cooling bath is removed and the reaction mixture allowed to warm up to room temperature. Heating to 40° C. for 30 minutes completes the reaction. After cooling to room temperature, the supernatant liquid is decanted and the residue washed with dichloromethane (2×5 ml). The organic layers are combined and the solvents removed by distillation at atmospheric pressure. The so-obtained oily residue is then purified by distillation yo yield 2.85 g of very hydroscopic 2,2-difluoro-4-pentenoic acid anhydride III, bp 78–80° C./20 Torr.

Provenance & Evidence