Acid-Catalyzed Z-E Isomerization of γ-Alkylidenebutenolides: An Experimental and DFT Study
作者:Jodieh Varejão、Luiz Barbosa、Eduardo Varejão、Aline Souza、Mateus Lage、José Carneiro
DOI:10.21577/0103-5053.20190131
日期:——
The Z-E isomerization of.-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using H-1 nuclear magnetic resonance (NMR) and high performance liquid chromatography ( HPLC) data as well as density functional theory (DFT) calculations at the omega B97x-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 gamma-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 gamma-alkylidenebutenolides are more stable in the Z form, protonation of the.-lactone carbonyl group results in preferential stabilization of the E isomer.