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Ring – Chain Tautomerism of 4-Hydroximino-hexahydropyrimidines Substituted in Position 2

✍ Scribed by Korbonits, Dezsö ;Tóbiás-Héja, Erzsébet ;Kolonits, Pαl

Publisher
Wiley (John Wiley & Sons)
Year
1991
Tongue
English
Weight
385 KB
Volume
124
Category
Article
ISSN
0009-2940

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✦ Synopsis

As shown by NMR spectroscopy, the reaction of 3-aminopropionamide oxime (9) with benzaldehyde or benzaldehyde derivatives 2a ~ d substituted with electron-attracting substituents affords products which exist as an equilibrium mixture of tautomers involving the open-chain 3-@enzylidenearnino)propionamide oximes 11 a -d and the cyclic 4-hydroximinohexahydropyrimidines 12a -d. Tautomers 11 and 12, isolated also in crystalline form, can be interconverted by using an appropiate solvent. In contrast, in the reaction of benzaldehydes substituted with electron-releasing groups (2 e, f) and cinnamaldehyde (2g) with 9 only the open-chain imines are formed, and in aprotic solvents no tautomerism can be ob- served.

Recently, we have reported on a ring-chain tautomerism of pyrimidines which is characteristic of pseudobases" and belongs to the exo') type as shown in Scheme 1. Scheme 1 R1 CXH Rl + ("x / N R2 H N=C 'R2

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