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Structural studies on 9‐hydrazono‐6,7,8,9‐tetrahydro‐4‐oxo‐4 H ‐pyrido[1,2‐ a ]pyrimidines by 1 H, 13 C and 15 N NMR spectroscopy
Author(s) -
Tóth Gábor,
Szöllösy ÁRon,
Almásy Attila,
Podányi Benjámin,
Hermecz István,
Breining Tibor,
Mészáros Zoltán
Publication year - 1983
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/omr.1270211111
Subject(s) - tautomer , steric effects , chemistry , substituent , hydrogen bond , solvation , carbon 13 nmr , nuclear magnetic resonance spectroscopy , proton , computational chemistry , stereochemistry , solvent , crystallography , molecule , organic chemistry , physics , quantum mechanics
1 H, 13 C and 15 N NMR studies demonstrated that 9‐hydrazono‐6,7,8,9‐tetrahydro‐4‐oxo‐4 H ‐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.