Trifluoromethanesulfonic anhydride → Methyl 2-fluoro-2-(trifluoromethyl)-3-butenoate

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Reaction Steps

Methyl 2-fluoro-2-trifluoromethyl-3-hydroxybutanoate (1 g) and pyridine (440 μl) in dichloromethane (5 ml) were stirred at -10° C. under nitrogen. Trifluoromethanesulphonic anhydride (900 μl) in dichloromethane (5 ml) was added dropwise and the resulting mixture stirred for 2 hours. The solution of methyl 2-fluoro-2-trifluoromethyl-3-trifluoromethylsulphonyloxybutanoate prepared in Step 1 was treated with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) (1.5 ml) and heated under reflux for 1 hour. Further DBU (1.5 ml) was added and the mixture left to stand at room temperature overnight. The red solution was washed with 5% aqueous HCl, saturated aqueous sodium bicarbonate (twice), dried (MgSO4) and concentrated at atmospheric pressure to give a red oil which was distilled using a Kugelrohr apparatus. The fraction distilling at 50° C. (air bath temperature) and at 100 mmHg was shown by NMR to be the desired product; 1H NMR (270 MHz; CDCl3) δ 3.92 (3H,s), 5.65(1H,dd), 5.81(1H,d), 6.08(1H,ddd) ppm. ##STR1##

Provenance & Evidence