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Substituent effects in the 1,3-dipolar cycloaddition reactions of 2-methylenecephalosporins with diazoalkanes

✍ Scribed by Pitlik, János ;Csaba Jászberényi, J. ;Komáromi, István

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
346 KB
Volume
1991
Category
Article
ISSN
0947-3440

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✦ Synopsis

Abstract

The 2‐methylenecephalosporins 1 undergo stereoselective 1,3‐dipolar cycloaddition reactions with diazoalkanes to give exclusively the spirocyclopropylcephalosporins 3. Substituens at C‐3, C‐4 and C‐7 of the cephalosporin nucleus do not display a significant effect on the reactivity of the 2‐exo double bond. However, reduction of the sulfoxides to sulfides has an inactivating influence. Reactions with substituted diazoalkanes proceed more slowly in every case. The results are explained by theoretical (PM3, AM1 and MNDO) calculations.

📜 SIMILAR VOLUMES

Cycloaddition reactions of cephalosporin
Cycloaddition reactions of cephalosporin compounds. IX—1H and 13C NMR stereochemical study of the 1,3-dipolar cycloadditions of diazoalkanes to 2-methylenecephem derivatives
✍ J. Cs. Jászberény; J. Pitlik; Gy. Batta; K. E. Kövér; K. Kollár 📂 Article 📅 1988 🏛 John Wiley and Sons 🌐 English ⚖ 498 KB

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.