Nuclear magnetic resonance and molecular modeling study of exocyclic carbon–carbon double bond polarization in benzylidene barbiturates

Benzylidene barbiturates are important materials for the synthesis of heterocyclic compounds with potential for the development of new drugs. The reactivity of benzylidene barbiturates is mainly controlled by their exocyclic carbon–carbon double bond. In this work, the exocyclic double bond polarization was estimated experimentally by NMR and correlated with the Hammett σ values of the aromatic ring substituents and the molecular modeling calculated atomic charge difference. It is demonstrated that carbon chemical shift differences and NBO charge differences can be used to predict their reactivity.

► Synthesis, NMR analysis and molecular modeling of benzylidene barbiturates. ► 13C chemical shift difference correlates well with Hammett σp and σm. ► Solvent interaction and conformation influence calculated NBO atomic charges. ► 13C chemical shift differences correlates well with NBO charge differences. ► Benzylidene barbiturates polarization defines their reactivity.