A series of known and novel 2‐methylenecephem derivatives were prepared and their reactions with diazomethane, phenyldiazomethane and diphenyldiazomethane were studied. The initially formed 1‐pyrazolino derivatives easily underwent spontaneous loss of nitrogen, leading to 2‐spirocyclopropylcephems. The two reaction products, formed in a 3:1 to 8:1 ratio on addition of diphenyldiazomethane, were separated by column chromatography and distinguished by their 1H and 13C NMR spectra. The 1H NMR spectra did not exclude the possibility of 1‐pyrazoline formation, but elemental analysis and 13C data corroborated the previous assumption that loss of nitrogen took place, even in those cases when it did not occur during the reaction.
ASJC Scopus subject areas
- Materials Science(all)