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Cycloaddition reactions of cephalosporin compounds. IX—1H and 13C NMR stereochemical study of the 1,3-dipolar cycloadditions of diazoalkanes to 2-methylenecephem derivatives

✍ Scribed by J. Cs. Jászberény; J. Pitlik; Gy. Batta; K. E. Kövér; K. Kollár

Publisher
John Wiley and Sons
Year
1988
Tongue
English
Weight
498 KB
Volume
26
Category
Article
ISSN
0749-1581

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✦ Synopsis

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 'H and 13C NMR spectra. The 'H 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.

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