Synthesis and study of conformation of 8-hydroxy-2-(2-(pyridin-4-yl)vinyl)quinoline by NMR spectroscopy correlation

Abstract

Reaction between 8-hydroxyquinaldine and 4-pyridincarboxaldehyde in acetic anhydride medium via Knoevenagel condensation can lead to the formation of different forms of styryl derivatives. 2-(2-(pyridine-4-yl)vinyl)quinolin-8-ol which received under different conditions has been studied with the help of two-dimensional NOESY H-H and J-resolved spectroscopy and gas- phase quantum chemical DFT-calculation methods. It has been found out that induction by light causes the formation of cis-form. At the same time trans-isomer is formed during the reaction conducted without any additional irradiation. Trans-isomer is formed due to the hydrochloride acid treatment of the reaction mixture. Calculations have shown that only two spatial forms, each of which is a mix of rotational conformers are possible out of two products configuration. In the spectra of each of the isomers cross-peaks are observed which are typical for the superposition of the configuration pair. It was shown that the transformation of a less stable form cis-isomer into trans-isomer also occurs when affected by light but with a longer wavelength. Refs 18. Figs 3. Table 1.