Competition between OH?O and multiple halogen–dipole interactions on the formation of intramolecular three-centred hydrogen bond in 3-acyl coumarins?

CrystEngComm Pub Date: 2009-03-31 DOI: 10.1039/B818309K

Abstract

This paper describes the synthesis and structural study in solution, by NMR, and in the solid state, by X-ray analysis, of 6-substituted (H, NO2, OCH3, Cl, Br) 2-oxo-2H-chromene-3-carboxylic acid (2-hydroxy-ethyl) amides. The results were supported by ab initio calculations at RHF-631G** level of theory. The crystal structures of compounds 6-Cl and 6-Br show deviations from the predicted theoretical conformation and also from that observed in solution, pointing to the influence exerted by intermolecular interactions on the molecular structure and on intramolecular three-centred hydrogen bond formation (O2?H12?O1). The significance of the plethora of non-covalent interactions [C?H?A (A = O, X, π), CO?CO, CO?π, C?X?OC (X = halogen), Br?Br and π?π stacking] is discussed.

Graphical abstract: Competition between OH?O and multiple halogen–dipole interactions on the formation of intramolecular three-centred hydrogen bond in 3-acyl coumarins
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