A Rapid Ultrasound Synthesis of Xanthenediones Catalyzed by Boric acid in Ethanol-Water Medium: Single Crystal, DFT and Hirshfeld Surface Analysis of Two Representative Compounds

Abstract A highly versatile and efficient ultrasound promoted synthesis of xanthenedione derivatives is achieved through condensation of dimedone with various aromatic aldehydes using boric acid as catalyst in ethanol-water medium. The advantages of this method being, mild reaction conditions, short reaction time, easy work-up, purification of products by non-chromatographic methods and additionally this method provides excellent yields. Two of the Xanthendiones derivatives 3a and 3b gave good crystals on recrystallization and their molecular structures were confirmed by crystallographic studies. The molecules in the crystal lattice are held together by weak intermolecular C-H•••O and C-H•••N interactions. Further insights into these interactions using Hirshfeld surface analysis and DFT/B3LYP studies show that in compound 3a H•••H (54.7%), O•••H (18.3%) and in 3b H•••H (53.7%), O•••H (17.6%) are the major contributors to the intermolecular interactions which stabilize the crystal structures. In order to determine molecular electrical transport properties, we studied the energy difference between Highest Occupied, HOMO, and Lowest Unoccupied, LUMO orbitals and the HOMO and LUMO energy gap for compounds 3a and 3b was found to be 3.9261 eV and 4.6436 eV respectively. The 2D fingerprint plot provided percentage contribution of each individual atom-to-atom interactions. The Mulliken atomic charges and molecular electrostatic potential on molecular van der Waals surface were calculated to know the electrophilic and nucleophilic regions of the molecular surface.