3.1. General Experimental

All chemicals, reagents and solvents were purchased from Sigma-Aldrich, Fisher Scientific, Alfa-Aesar, Fluka and Acros Chemicals. Whenever required, solvents were dried prior to use as described by the handbook Purification of Laboratory Chemicals and stored over 4Å molecular sieves under nitrogen. Flash column chromatography was performed with silica gel (230–400 mesh) (Merck) and TLC was performed on pre-coated silica gel plates (Merck Kiesel gel 60F254, BDH). Melting points were determined on an electrothermal instrument (Gallenkamp) and are uncorrected. Compounds were visualized by irradiation with UV light at 254 nm and 365 nm. The NMR spectra of all new compounds were recorded on a Bruker AVANCE DPX500 spectrometer operating at 500 and 125 MHz for ¹H and ¹³C NMR, respectively, and auto calibrated to the deuterated solvent reference peak (Supplementary Materials; Figure S2). Chemical shifts are given in δ relative to tetramethylsilane (TMS); the coupling constants (J) are given in Hertz. TMS was used as an internal standard (δ = 0 ppm) for ¹H NMR and CDCl₃ served as an internal standard (δ = 77.0 ppm) for ¹³C NMR. Multiplicity is denoted as s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet) or combinations thereof. The compounds imines 11a–f and aldehydes 12a–f were prepared according to Kishk et al. [29]. The DI Analysis Shimadzu QP2010-Plus^® GC/MS (Shimadzu^TM, Tokyo, Japan) was adopted for recording the low-resolution mass spectra (MS) of the synthesized compounds at electron impact (EI⁺) mode. Regarding purity analysis, the elemental analyses were recorded on Vario^® EL-CHNS Elemental Analyzer (GmbH^TM, Hanau, Germany). The results of elemental analyses (C, H, N) were found to be in good agreement (±0.45%) with the calculated values. All compounds were >95% pure.