Abstract
The crystal structures of two chromone derivatives, viz. ethyl 6-(4-methyl-phen-yl)-4-oxo-4H-chromene-2-carboxyl-ate, C19H16O4, (1), and ethyl 6-(4-fluoro-phen-yl)-4-oxo-4H-chromene-2-carboxyl-ate C18H13FO4, (2), have been determined: (1) crystallizes with two mol-ecules in the asymmetric unit. A comparison of the dihedral angles beween the mean planes of the central chromone core with those of the substituents, an ethyl ester moiety at the 2-position and a para-substituted phenyl ring at the 6-position shows that each mol-ecule differs significantly from the others, even the two independent mol-ecules (a and b) of (1). In all three mol-ecules, the carbonyl groups of the chromone and the carboxyl-ate are trans-related. The supra-molecular structure of (1) involves only weak C-H⋯π inter-actions between H atoms of the substituent phenyl group and the phenyl group, which link mol-ecules into a chain of alternating mol-ecules a and b, and weak π-π stacking inter-actions between the chromone units. The packing in (2) involves C-H⋯O inter-actions, which form a network of two inter-secting ladders involving the carbonyl atom of the carboxyl-ate group as the acceptor for H atoms at the 7-position of the chromone ring and from an ortho-H atom of the exocyclic benzene ring. The carbonyl atom of the chromone acts as an acceptor from a meta-H atom of the exocyclic benzene ring. π-π inter-actions stack the mol-ecules by unit translation along the a axis.
Highlights
Bioquımica, Faculdade de Ciências, Universidade do Porto, 4169-007 Porto, Portugal. *Correspondence e-mail: The crystal structures of two chromone derivatives, viz. ethyl 6-(4-methylphenyl)-4-oxo-4H-chromene-2-carboxylate, C19H16O4, (1), and ethyl 6-(4-fluorophenyl)-4-oxo-4H-chromene-2-carboxylate C18H13FO4, (2), have been determined: (1) crystallizes with two molecules in the asymmetric unit
The packing in (2) involves C—H O interactions, which form a network of two intersecting ladders involving the carbonyl atom of the carboxylate group as the acceptor for H atoms at the 7-position of the chromone ring and from an ortho-H atom of the exocyclic benzene ring
The carbonyl atom of the chromone acts as an acceptor from a meta-H atom of the exocyclic benzene ring. – interactions stack the molecules by unit translation along the a axis
Summary
Benzopyran derivatives represent a large class of natural and synthetic heterocycles that are often linked to a broad array of biological activities, (Gaspar et al, 2014, 2015) Within this vast class of compounds, the chromone core has emerged as a privileged structure for drug discovery and development programs (Welsch et al, 2010). E72, 8–13 research communications to Alzheimer’s and Parkinson’s diseases, namely as adenosine receptors ligands (Cagide et al, 2015a) and/or as monoamino oxidase B inhibitors, (Cagide et al, 2015b) Within this framework, our project has been focused on the discovery of new chemical entities based on a chromone scaffold. We describe the crystal structures of two new chromone derivatives, viz. ethyl-6-(4-methylphenyl)-4-oxo4H-chromene-2-carboxylate (1) and ethyl-6-(4-fluorophenyl)4-oxo-4H-chromene-2-carboxylate (2)
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