A Stereoselective Synthesis of a Novel α,β-Unsaturated Imine-Benzodiazepine through Condensation Reaction, Crystal Structure, and DFT Calculations

The stereoisomers (E)-2,2-dimethyl-4-(4-subsitutedstyryl)-2,3-dihydro-1H-[1,5]-benzodiazepine <b>3(a-d)</b> were synthesized via the condensation reaction of 2,2,4-trimethyl-2,3-dihydro-1H-1,5-benzodiazepine (BZD) <b>1</b> with the benzaldehyde derivatives <b>2(a-d)</b> in ethanol. The chemical structure of the prepared products was confirmed by NMR (¹H and ¹³C), HRMS, and X-ray analysis of the crystal structure <b>3d</b>. The condensation reaction was examined using DFT calculations at the theoretical level of B3LYP/6-31G(d) to elucidate the chemo-, regio-, and stereoselectivity and the reaction mechanism of the produced isomer. Furthermore, we identified each reagent's reactive sites by the measurement of the reactivity indices. We also looked at how the electron-withdrawing groups (EWGs) of various aldehydes affected the reaction's mechanism and the stability of products <b>3(a-d)</b>.