The 9-phenylaminotetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones (4)-(9), synthesized from the 9-bromo compounds (1)-(3), displayed imine-enamine tautomerism. In solution (if R2 ≠ H) the equilibrium mixtures contain both cis- and trans-imines. The enamine form is stabilized by increasing polarity of the solvent and by increasing the electron-withdrawing effect of substituent R1. Owing to 1,3-allylic strain, in the derivatives where R2 = Me the imine form is energetically less favoured than in the derivatives with R2 = H. The chemical structures of the synthesized products were studied by u.v., 1H and 13C n.m.r. spectroscopy.
|Number of pages||4|
|Journal||Journal of the Chemical Society, Perkin Transactions 1|
|Publication status||Published - 1985|
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