Phosphorus oxychloride → Chloro-N,N-dimethylformiminium chloride

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Reaction Steps

Vilsmeier reagent was prepared from N,N-dimethylformamide (0.31 g) and phosphorus oxychloride (0.64 g) in a usual manner. 2-tert-butoxycarbonylmethoxyimino-2-(1,2,4-thiadiazol-3-yl)acetic acid (syn isomer) (1.0 g) was added to a stirred suspension of the Vilsmeier reagent prepared above in ethyl acetate (11 ml) under ice-cooling, and the stirring was continued for 30 minutes at the same temperature to produce an activated acid solution. N-Trimethylsilylacetamide (3.2 g) was added to a stirred suspension of 7-amino-3-cephem-4-carboxylic acid (0.7 g) in ethyl acetate (20 ml), and the stirring was continued at 40° to 43° C. for 30 minutes. To this solution was added the above activated acid solution at -10° C., followed by stirring at the same temperature for 30 minutes. Water (10 ml) was added to the resultant solution, and the separated organic layer was washed with water, dried over magnesium sulfate and then evaporated to give 7-[2-tert-butoxycarbonylmethoxyimino-2-(1,2,4-thiadiazol-3 -yl)acetamido]-3-cephem-4-carboxylic acid (syn isomer) (1.4 g).

Provenance & Evidence