A detailed structural analysis of selected (oxiran-2-yl)methoxy- and 3-chloro-2-hydroxypropoxycoumarin

• We report coumarins with oxiran-2-ylethoxy or 3‑chloro-2-hydroxypropoxy moieties. • The structures of 4 new compounds were studied with X-ray diffraction technique. • The structures of 14 compounds were studied with 1 H, 13 C NMR and HRMS spectra. • We supplemented the data for 5 compounds, previously described in the literature. A series of intermediate compounds from the synthesis of seven different coumarin derivatives bearing (oxiran-2-yl)methoxy or 3‑chloro-2-hydroxypropoxy moieties have been synthesized. All compounds have been separated and characterized by 1 H, 13 C NMR and high resolution mass spectra (HRMS). Crystals of two pairs of compounds ( 1 a,b and 4 a,b ): 6-acetyl-4,7-dimethyl-5-(oxiran-2-ylmethoxy)-2 H -chromen-2-one ( 1a ), 6-acetyl-5-(3‑chloro-2‑hydroxy propoxy)-4,7-dimethyl-2 H -chromen-2-one ( 1b ), 8-acetyl-4-methyl-7-(oxiran-2-ylmethoxy)-2 H -chromen-2-one ( 4a ), 8-acetyl-7-(3‑chloro-2-hydroxypropoxy)-4-methyl-2 H -chromen-2-one ( 4b ) were investigated using single crystal X-ray diffraction technique. Determined molecular structures confirm the precision of the synthesis process and show that the crystal structures are stabilized by π-stacking interactions. Theoretical DFT calculations reveal the molecular basis behind the ratio of the (oxiran-2-yl)methoxy derivatives versus the 3‑chloro-2-hydroxypropoxy ones.