Structural studies on 9-hydrazono-6,7,8,9-tetrahydro-4-oxo-4H-pyrido[1,2-a]pyrimidines by 1H, 13C and 15N NMR spectroscopy |
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| Authors: | Gbor Tth Ron Szllsy Attila Almsy Benjmin Podnyi Istvn Hermecz Tibor Breining Zoltn Mszros |
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| Institution: | Gábor Tóth,ÁRon Szöllösy,Attila Almásy,Benjámin Podányi,István Hermecz,Tibor Breining,Zoltán Mészáros |
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| Abstract: | 1H, 13C and 15N NMR studies demonstrated that 9-hydrazono-6,7,8,9-tetrahydro-4-oxo-4H-pyrido-1,2-a] pyrimidlnes exist as an equilibrium mixture of Z-E isomers in the hydrazono–imino tautomeric form having an exocyclic double bond. Proton-catalysed Z-E interconversion is fast. Substituent and solvent effects revealed that the decisive factors controlling the Z:E ratio are internal hydrogen bonding in the Z-isomer, stabilization by solvation and steric interaction. |
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