Phosphorus oxychloride → Benzhydryl 7-(4-bromo-2-methoxyiminoacetoacetamido)-3-vinyl-3-cephem-4-carboxylate

Beteiligte Stoffe

Reaktionsschritte

Vilsmeir reagent, which was prepared from N,N-dimethylformamide (0.48 g) and phosphorus oxychloride (1.0 g), was suspended in ethyl acetate (20 ml), and thereto was added 4-bromo-2-methoxyiminoacetoacetic acid (syn isomer) (1.34 g) under ice-cooling, followed by stirring at the same temperature for half an hour to prepare the activated acid solution. This solution was added to a solution of benzhydryl 7-amino-3-vinyl-3-cephem-4-carboxylate hydrochloride (2.15 g) and trimethylsilylacetamide (3.93 g) in ethyl acetate (30 ml) at -20° C., and the mixture was stirred at -20° to 0° C. for 1.5 hours. To the reaction mixture was added ethyl acetate (100 ml) and water (100 ml), and the separated ethyl acetate solution was washed with a saturated aqueous sodium bicarbonate and an aqueous sodium chloride, followed by drying over anhydrous magnesium sulfate. Removal of the solvent gave a residue, which was washed with diethyl ether to obtain benzhydryl 7-(4-bromo-2-methoxyiminoacetoacetamido)-3-vinyl-3-cephem-4 -carboxylate (syn isomer) (2.5 g).

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