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A new ring transformation: Synthesis of 5,5-dimethyl-3-oxo-1-pyrroline 1-oxides from 6,6-dimethyl-4-oxo-5,6-dihydro-1,2,4h-oxazines

✍ Scribed by Christian Deshayes; Suzanne Gelin

Publisher
Elsevier Science
Year
1981
Tongue
French
Weight
358 KB
Volume
22
Category
Article
ISSN
0040-4039

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✦ Synopsis

The nitrosation of some y,&unsaturated B-diketo compounds affords the 3-substituted 4-oxo-5,6-dihydro-1,2,4ff-oxaxines. These compounds are converted to the isomeric 3-oxo-1-pyrroline l-oxides by a facile thermal rearrangement. In connection with our study of y,s-unsaturated 6-ketoesters1'2, we have explored their nitrosation. We report here the preparation of 4-0x0-5,6-dihydro-1,2,4H-oxazine derivatives. We have observed one unusual transformation of this novel heterocyclic system into the isomeric 3-oxo-I-pyrroline l-oxides. No evidence of this type of ring contraction was found in the literature3. It is well known that the nitrosation of e-diketo compounds leads to the a-hydroxyimino derivatives4a. Treatme nt of substances 1 with nitrous acid affords a material

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