Methyl 3-aminoacrylate, mixture of E and Z isomers

Electron Delocalization in Push-Pull Alkenes Including Methyl 3-Aminoacrylate

Džambaski, Zdravko, et al. ChemistrySelect, 2017, 2(1), 42-50.

This work used NBO analysis at the DFT level to study the backward π electron delocalization from the electron accepting group (Acc) to the C=C bond, which was rarely mentioned in electron-deficient and push-pull alkenes, and discusses the nature and number of the Acc group, s-cis/s-trans and Z/E isomers.
The study showed that the energy provided by the π electron donated by Acc to the C=C double bond in the push-pull system can reach up to 10% of the total π electron stabilization energy. The π electron donation of the Acc→C=C bond is more pronounced in the s-trans conformational arrangement compared to the s-cis conformation. However, in push-pull alkenes, this donation is less influenced by Z/E isomerism, with a slightly higher intensity observed in Z isomers.
Among them, methyl 3-aminoacrylate (5b) is a push-pull alkene. The hydrogen bond structure in methyl 3-aminoacrylate (5b) is the global minimum, and the energy difference of other conformers is > 3.1 kcal/mol.
In addition, the planar E s-trans and E s-cis forms of methyl 3-aminoacrylate (5b) are transition structures for nitrogen transformation with fairly low barriers of 0.03 kcal/mol and 0.01 kcal/mol, respectively. The sum of the bond angles of the amino group is 356.6° (E s-trans) and 357.7° (E s-cis).