Synthesis, experimental and DFT studies on crystal structure, FT-IR, 1H, and 13C NMR spectra, and evaluation of aromaticity of three derivatives of xanthens

Several derivatives of xanthenes are prepared by the condensation of aldehydes and dimedone in H2O in the presence of a catalytic amount of trichlorotriazine. The crystalline products were characterized by FTIR, H-1, and C-13 NMR spectra. Density Functional Theory (DFT) calculations on the B3LYP level were used to optimize the geometry and calculate the crystal structure, FTIR, H-1 NMR and C-13 NMR spectra of the selected synthesized compounds. We found that the values of FTIR, H-1, and C-13 NMR spectra obtained by the B3LYP method are in accordance with experimental data. The calculated NICS indicate that the six-membered rings in xanthenes are essentially homoaromatic.