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On the Preparation of 2‐Substituted Cephalosporins, Part 2
Author(s) -
Tamás László,
Gunda Tamás E.,
Batta Gyula,
Sztaricskai Ferenc
Publication year - 2003
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200390018
Subject(s) - chemistry , diazomethane , cycloaddition , moiety , cephalosporin , cephem , enol , substituent , enone , medicinal chemistry , ethyl diazoacetate , keto–enol tautomerism , organic chemistry , stereochemistry , cyclopropanation , catalysis , tautomer , carboxylic acid , biochemistry , antibiotics
Cephalosporin sulfoxides 1 and 2 containing an enone‐ or dienone‐type moiety at position 2 were treated with 2,3‐dimethylbuta‐1,3‐diene or diethyl azodicarboxylate to synthesize, in DielsAlder reactions, the new cephalosporin derivatives 4 and 5 with a cyclic substituent ( Scheme 1 ). Under the same conditions, ethyl diazoacetate and diazomethane reacted differently: while reactions of 1 and 3 with the former lead to compounds 7 – 10 corresponding to the 1,3‐dipolar cycloaddition route ( Scheme 2 ), diazomethane produced only enol ethers 12 and 13 , respectively ( Scheme 3 ). This difference could be rationalized by assuming two different reaction pathways: an orbital‐symmetry‐controlled concerted cycloaddition and an ionic one.