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

Beteiligte Stoffe

Reaktionsschritte

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

Herkunft & Nachweise