Phosphorus oxychloride → Chloro-N,N-dimethylformiminium chloride

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Reaction Steps

Vilsmeier reagent was prepared from phosphorus oxychloride (14.8 g) and N,N-dimethylformamide (7.07 g) in ethyl acetate (50 ml) in a conventional manner. 2-(tert-Butoxycarbonylmethoxyimino)-2-(formamidothiazol-4-yl)acetic acid (syn isomer)(29 g) was added to the stirred suspension of Vilsmeier reagent in ethyl acetate (250 ml) under ice-cooling and stirred for 30 minutes at same temperature to prepare an activated acid solution. On the other hand, benzhydryl 7-amino-3-chloromethyl-3-cephem-4-carboxylate monohydrochloride (36.1 g) was dissolved in a solution of trimethylsilylacetamide (63 g) in ethyl acetate (400 ml). To this solution was added the above activated acid solution at -12° C. and the mixture was stirred for an hour at -20° to 0° C. Water was added to the reaction mixture at 0° C. The organic layer was separated, washed with a saturated aqueous sodium bicarbonate and an aqueous sodium chloride. The solution was dried over magnesium sulfate and evaporated under reduced pressure. The residue was pulverized with diethyl ether to give benzhydryl 7-[2-tert-butoxycarbonylmethoxyimino-2-(2-formamidothiazol-4-yl)acetamido]3-chloromethyl-3-cephem-4-carboxylate (syn isomer) (49.7 g).

Provenance & Evidence