Synthesis, Spectral Characterization and Computational DFT Analysis of Benzylideneisophorone Derivatives

The high-resolution ¹H NMR spectra of (E)-5,5-dimethyl-3-(4-(methylthio)styryl)cyclohex-2-enone (1) and (E)-3-(4-(diethoxymethyl)styryl)-5,5-dimethylcyclohex-2-enone (2) are presented in Plates 3 and 4, respectively. The ¹H NMR signals were assigned based on their chemical shifts, integration values, multiplicities, and coupling constants. The carbon atom numbering is illustrated in the reaction scheme, and the corresponding proton assignments were made accordingly. Among the observed signals, two characteristic doublets appearing at δ 6.77 ppm (J = 16 Hz) and δ 6.89 ppm (J = 16 Hz), each integrating for one proton, were assigned to the olefinic (vinylic) protons of the α,β-unsaturated system. The presence of these doublets confirms the successful formation of the condensation product. Furthermore, the large coupling constant (J = 16 Hz) is characteristic of trans-coupled olefinic protons, providing strong evidence for the formation of the thermodynamically more stable (E)-isomer rather than the (Z)-isomer.