A three-step pathway from (2′-amino)chalcones to novel styrylquinoline–chalcone hybrids : synthesis and spectroscopic and structural characterization of three examples

Abstract

Three new styryl­quinoline–chalcone hybrids have been synthesized using a three-step pathway starting with Friedländer cyclo­condensation between (2-amino­phen­yl)chalcones and acetone to give 2-methyl-4-styryl­quinolines, followed by selective oxidation to the 2-formyl analogues, and finally Claisen–Schmidt condensation between the formyl inter­mediates and 1-acetyl­naph­tha­lene. All inter­mediates and the final products have been fully characterized by IR and 1H/13C NMR spectroscopy, and by high-resolution mass spectrometry, and the three products have been characterized by single-crystal X-ray diffraction. The mol­ecular conformations of (E)-3-{4-[(E)-2-phenyl­ethen­yl]quinolin-2-yl}-1-(naph­tha­len-1-yl)prop-2-en-1-one, C30H21NO, (IVa), and (E)-3-{4-[(E)-2-(4-fluoro­phen­yl)ethen­yl]quinolin-2-yl}-1-(naph­tha­len-1-yl)prop-2-en-1-one, C30H20FNO, (IVb), are very similar. In each com­pound, the mol­ecules are linked into a three-dimensional array by hydro­gen bonds, of the C—H...O and C—H...N types in (IVa), and of the C—H...O and C—H...π types in (IVb), and by two independent π–π stacking inter­actions. By contrast, the conformation of the chalcone unit in (E)-3-{4-[(E)-2-(2-chloro­phen­yl)ethen­yl]quinolin-2-yl}-1-(naph­tha­len-1-yl)prop-2-en-1-one, C30H20ClNO, (IVc), differs from those in (IVa) and (IVb). There are only weak hydro­gen bonds in the structure of (IVc), but a single rather weak π–π stacking inter­action links the mol­ecules into chains. Comparisons are made with some related structures.