Synthesis and spectroscopic and structural characterization of three new 2-methyl-4-styrylquinolines formed using Friedländer reactions between (2-aminophenyl)chalcones and acetone

Abstract

Three new 2-methyl-4-styrylquinoline derivatives have been synthesized in high yields using Friedländer reactions between chalcones [1-(2-aminophenyl)-3-arylprop-2-en-1-ones] and acetone, and characterized using IR, 1H and 13C NMR spectroscopy, and mass spectrometry, and by crystal structure analysis. In (E)-4-(4-fluorostyryl)-2-methylquinoline, C18H14FN, (I), the molecules are joined into cyclic centrosymmetric dimers by C—H...N hydrogen bonds and these dimers are linked into sheets by π–π stacking interactions. The molecules of (E)-2-methyl-4-[4-(trifluoromethyl)styryl]quinoline, C19H14F3N, (II), are linked into cyclic centrosymmetric dimers by C—H...π hydrogen bonds and these dimers are linked into chains by a single π–π stacking interaction. There are no significant hydrogen bonds in the structure of (E)-4-(2,6-dichlorostyryl)-2-methylquinoline, C18H13Cl2N, (III), but molecules related by translation along [010] form stacks with an intermolecular spacing of only 3.8628 (2) Å. Comparisons are made with the structures of some related compounds.

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

“…The main spectroscopic features for the precursors (IIa) and (IIc) matched perfectly those of previously reported analogues (Vera et al, 2022). The IR spectra of the formyl intermediates (III) showed the characteristic absorption band for the C O group at 1699-1708 cm À 1 , and their 1 H and 13 C NMR spectra contained the corresponding signals for the formyl group in the ranges � 10.…”

“…This synthetic pathway (see Scheme 1) is extremely versatile, in that it permits the introduction of substituents in both rings of the quinoline portion (cf. Rodrı ´guez et al, 2020), as well as in the styryl component (Vera et al, 2022), while the Claisen-Schmidt reaction step introduces a very wide range of synthetic options. In addition, the presence of the chalcone unit in the compounds of type (IV) provides scope for an extensive variety of further synthetic elaborations utilizing this fragment (Powers et al, 1998;Mohamed & Abuo-Rahma, 2020).…”

“…Compounds (IIa) and (IIc) were prepared using the procedure recently described by Vera et al (2022) for the synthesis of compound (IIb).…”

“…We have recently reported (Vera et al, 2022) the structures of a number of 2-methyl-4-styrylquinolines of type (II) (see Scheme 1; all prepared using Friedla ¨nder cyclocondensation reactions, as here). In each of (E)-4-(4-fluorostyryl)-2methylquinoline and (E)-2-methyl-4-[4-(trifluoromethyl)styryl]quinoline, the molecules are linked into cyclic centrosymmetric dimers by hydrogen bonds, of the C-H� � �N and C-H� � �� types, respectively, and these dimers are further linked by �-� stacking interactions to form sheets in the fluoro compound and chains in the trifluoromethyl analogue.…”

Synthesis, and spectroscopic and structural characterization of three new styrylquinoline–benzimidazole hybrids

“…In each compound, the styrylquinoline fragment is nonplanar, as indicated by the values of the C3-C4-C41-C42 torsion angle (Table 2). We have noted previously (Vera et al, 2022) that 4-styrylquinoline derivatives typically have nonplanar skeletons, whereas 2-styrylquinolines and 8-styrylquinolines typically have planar skeletons.…”