Phosphorus oxychloride → Chloro-N,N-dimethylformiminium chloride

Participants

Reaction Steps

The Vilsmeier reagent was prepared from dimethylformamide (0.44 g) and phosphorus oxychloride (0.92 g) in the conventional manner, and thereto was added ethyl acetate (20 ml). To the mixture was added 2-isopropoxyimino-2-(2-formylaminothiazol-4-yl)acetic acid (syn isomer), which can be represented as 2-isopropoxyimino-2-(2-formylimino-2,3-dihydrothiazol-4-yl)acetic acid (syn isomer), (1.29 g) under cooling at -5° to 0° C. with stirring and then stirring was continued for 20 minutes to give a clear solution. Thus obtained solution was added at a time to solution, which was prepared by warming a mixture of 2-methyl-7-amino-3-cephem-4-carboxylic acid (1.44 g) and trimethylsilylacetamide (4.6 g) in ethyl acetate (30 ml) at 40° C. followed by stirring for 30 minutes, under cooling at -20° to -15° C. with stirring. The resulting mixture was stirred for 1.5 hours at the same temperature and thereto was added water (20 ml). The mixture was stirred for 20 minutes at room temperature. The precipitates were collected by filtration, washed with a small amount of ethyl acetate, washed well with water and then dried to give 2-methyl-7-[2-isopropoxyimino-2-(2-formylaminothiazol-4-yl)acetamido]-3-cephem-4-carboxylic acid (syn isomer), which can be represented as 2-methyl-7-[2-isopropoxyimino-2-(2-formylimino-2,3-dihydrothiazol-4-yl)acetamido]-3-cephem-4-carboxylic acid (syn isomer), (1.8 g).

Provenance & Evidence