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5(4H)-Oxazolones. Part X. Acid and base effects on the translactonization reaction of 4-(2-Oxa-alkylidene)-5(4H)-oxazolones: New synthesis of 5-alkylidene-3-benzoylamino-2(5H)-furanones

✍ Scribed by Maria Luisa Gelmi; Francesca Clerici; Alessandra Melis

Publisher
Elsevier Science
Year
1997
Tongue
French
Weight
757 KB
Volume
53
Category
Article
ISSN
0040-4020

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✦ Synopsis

A bstract:~(Z-Oxa-alkylidene)-~4~~x~olones (azlactones) 1 can be transformed in acidic conditions (anhydrous HBrlCHC13) into 5-alkylidene-3-benzoyI~~2(S~-furawnes 2 which have Z configuration at the exocyclic double bond. The same reaction conducted in acetic acid as solvent gives. besides the alkyhdene-fumnones 2, the furanyl acetates 5. The result of azlactone transformation in the presence of base (DBU) depends on the steric hindrances in the starting material. The less hindered oxazolones la,b give condensation products 8, whereas the more hindered azlactone lc gives fnranone 2c or, in presence of an alkylating agent, fwanone 2d.

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