Acid-Catalyzed Z-E Isomerization of γ-Alkylidenebutenolides: An Experimental and DFT Study

The Z-E isomerization of γ-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using 1H nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC) data as well as density functional theory (DFT) calculations at the wB97x-D/6-31...

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Bibliographic Details
Published in:Journal of the Brazilian Chemical Society 2020, Vol.31 (1), p.90-99
Main Authors: Varejão, Jodieh, Barbosa, Luiz, Varejão, Eduardo, Souza, Aline, Lage, Mateus, Carneiro, José
Format: Article
Language:English
Subjects:
CHEMISTRY, MULTIDISCIPLINARY
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Summary:The Z-E isomerization of γ-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using 1H nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC) data as well as density functional theory (DFT) calculations at the wB97x-D/6-31G(d,p) level, including solvent effects with the polarizable continuum solvation approach. The experimental data supported the Z to E isomerization of γ-alkylidenebutenolides under acid catalysis. Newly prepared samples have predominantly Z configuration, which partially isomerizes to the E isomer under acidic conditions. Density functional theory studies corroborate the experimental findings. While neutral γ-alkylidenebutenolides are more stable in the Z form, protonation of the γ-lactone carbonyl group results in preferential stabilization of the E isomer.
ISSN:0103-5053
1678-4790
DOI:10.21577/0103-5053.20190131