反应详情

3.05 g of N-bromosuccinimide were added portionwise over 1.75 hours to an ice-cold solution of 4.6 g of t-butyl 2-bromo-3-methyl-7-phenylacetamido-3-cephem-4-carboxylate-1-oxide in 350 ml of dichloromethane under the exposure to light of a tungsten lamp of 150 W. After the addition of N-bromosuccinimide was complete, the exposure was continued for one hour and the orange colored solution was evaporated to dryness under vacuo at low temperature. The residue was chromatographed over silica gel, using as initial eluent a 72:1 mixture of methylene chloride and acetone and then a 49:1 mixture of the same components to obtain 1.4 g of t-butyl 2-bromo-3-bromomethyl-7-phenylacetamido-3-cephem-4-carboxylate-1-oxide by evaporation to dryness of the suitable fractions.

1. customthe orange colored solution was evaporated to dryness under vacuo at low temperature
2. customThe residue was chromatographed over silica gel
3. additiona 72:1 mixture of methylene chloride and acetone
4. additiona 49:1 mixture of the same components