Syntheses and Crystal Structures of Three 4-((Quinolin-8-yloxy)methyl)-2H-chromen-2-one Derivatives

Abstract

Three coumarin and 8-hydroxyquinoline hybrids each linked by a methylene bridge were synthesized under Pechmann cyclisation conditions and crystals were grown to study their structural features. All three compounds, 7-methyl-4-((quinolin-8-yloxy)methyl)-2H-chromen-2-one, 2a, 5,7-dimethyl-4-((quinolin-8-yloxy)methyl)-2H-chromen-2-one, 2b and 6-chloro-4-((quinolin-8-yloxy)methyl)-2H-chromen-2-one, 2c, crystallised in the monoclinic crystal system. In each molecule, a quinoline ring system binds to a chromen-2-one sub-unit through an O–CH₂ bridge with the molecules distinguished by the substitution pattern on the benzene ring of the chromen-2-one ring system. All three molecules are reasonably planar. The crystal packing in these molecules is dominated by inversion dimer formation involving both non-classical hydrogen bonds and extensive offset π···π stacking interactions. For 2b and 2c, C–H···π contacts are also found.

Graphical Abstract

Inversion dimer formation and π···π contacts are particularly important in the crystal packing of three coumarin and 8-hydroxyquinoline hybrids reported here.