Water → Chloro-N,N-dimethylformiminium chloride

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Reaction Steps

The Vilsmeier reagent was prepared from N,N-dimethylformamide (0.32 g.) and phosphoryl chloride (0.67 g.) in a conventional manner. After the reagent was suspended in ethyl acetate (10 ml.), 2-(2-formamidothiazol-4-yl)-2-(2,2,2-trifluoroethoxyiminoacetic acid (syn isomer, 1.2 g.) was added to the stirred suspension under ice cooling and stirred at the same temperature for 30 minutes. The solution was added to a solution of 7-amino-3-cephem-4-carboxylic acid (0.8 g.), and trimethylsilylacetamide (4.2 g.) in ethyl acetate (20 ml.) at -25° C., and stirred at -20° to -10° C. for an hour. Water and ethyl acetate were added to the resultant solution, and ethyl acetate layer was separated. The aqueous layer was extracted again with ethyl acetate. Water was added to the combined extract and adjusted to pH 7.5 with a saturated aqueous solution of sodium bicarbonate, and then the aqueous layer was separated. Ethyl acetate was added to the aqueous layer, adjusted to pH 1.5 with hydrochloric acid and the ethyl acetate layer was separated. The aqueous layer was extracted again with ethyl acetate. The extracts were combined, washed with a saturated aqueous solution of sodium chloride and dried over magnesium sulfate. After concentrating the solution in vacuo, the residue was triturated with diethyl ether, and the precipitates were collected by filtration and dried to give 7-[2-(2-formamidothiazol-4-yl)-2-(2,2,2-trifluoroethoxyimino)acetamido]-3-cephem-4-carboxylic acid (syn isomer, 1.55 g.).

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