Novel tandem Knoevenagel-Michael condensation product of naphtho[2,1-b]furan-2-carbaldehyde with dimedone: Synthesis, spectroscopic and crystal structure studies

Abstract

Abstract 2,2′-Napthfuranyl bis(3‑hydroxy-5,5-dimethyl-2-cyclohexene-1-one) (2) was obtained in one pot via condensation between naphtho[2,1-b]furan-2-carbaldehyde (1) and dimedone. Instead of the Knoevenagel condensation product, (2) was obtained via tandem Knovenegel-Michael reaction. The reaction went effortlessly even in the absence of a strong base/catalyst and in short duration. Cyclisation of (2) to yield the expected xanthene derivative did not occur even after the reflux was carried out with Conc. HCl and H2SO4. The crystal structure of (1) was studied by single crystal X-ray diffraction technique (SCXRD). Further, (2) was characterized by FTIR, 1H & 13C NMR, mass spectral analysis, and, further by SCXRD. Crystal structure of (1) features several CH…O, CH…π and many π…π interactions resulting in a complex three dimensional (3D) architecture, while, in (2), whose molecular conformation is stabilized by two intramolecular OH…O hydrogen bonds, CH…O and π…π interactions form 1D ribbon like architecture. Hirshfeld surface analyses were also performed.