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

Abstract

Three new 4-styrylquinoline–benzimidazole hybrids have been synthesized using a reaction sequence in which 2-methylquinoline precursors first undergo selective oxidation by selenium dioxide to form the corresponding 2-formylquinoline intermediates, followed by oxidative cyclocondensation reactions with benzene-1,2-diamine to yield the hybrid products. The formyl intermediates and the hybrid products have all been fully characterized using a combination of IR, 1H and 13C NMR spectroscopy, and high-resolution mass spectrometry, and the structures of the three hybrid products have been determined using single-crystal X-ray diffraction. Ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(4-chlorostyryl)quinoline-3-carboxylate, C27H20ClN3O2, (IIIa), and ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(2-methoxystyryl)quinoline-3-carboxylate, C28H23N3O3, (IIIb), both crystallize in the solvent-free form with Z′ = 1, but ethyl (E)-2-(1H-benzo[d]imidazol-2-yl)-4-(4-methylstyryl)quinoline-3-carboxylate, C28H23N3O2, (IIIc), crystallizes as a partial hexane solvate with Z′ = 3, and the ester group in one of the independent molecules is disordered over two sets of atomic sites having occupancies of 0.765 (7) and 0.235 (7). The molecules of (IIIc) enclose continuous channels which are occupied by disordered solvent molecules having partial occupancy. In all of the molecules of (IIIa)–(IIIc), the styrylquinoline fragment is markedly nonplanar. Different combinations of N—H...O and C—H...π hydrogen bonds generate supramolecular assemblies which are two-dimensional in (IIIb) and (IIIc), but three-dimensional in (IIIa). Comparisons are made with the structures of some related compounds.

Conversion of 2-methyl-4-styrylquinolines into 2,4-distyrylquinolines: synthesis, and spectroscopic and structural characterization of five examples

“…In each of (IIa)-(IIe), the 2-styryl unit is close to being coplanar with the quinoline unit, while the 4-substituent is twisted well out of the plane of the quinoline unit. These observations thus complement the general pattern in styrylquinolines that we have noted previously (Vera et al, 2022;Ardila et al, 2022). Amongst the styrylquinolines whose structures are recorded in the Cambridge Structural Database (Groom et al, 2016), 2-styryl-and 8-styrylquinolines all have…”

“…The work reported here can be regarded as a continuation of an earlier crystallographic study which reported the structures of 4-styrylquinolines having different substituents at the C2 and C3 positions (Rodrı ´guez et al, 2020;Vera et al, 2022;Ardila et al, 2022).…”

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

“…For each of (IVa)-(IVc), the atom labelling (Figs. 1-3) follows that employed in recent reports on styrylquinoline derivatives (Vera et al, 2022;Ardila et al, 2022). Compounds (IVa) and (IVb) are both triclinic (Table 1), and their corresponding unit-cell repeat distances are fairly similar; however, these compounds are not isomorphous, as the inter-axial angles in (IVa) are all less than 90 � , whereas those in (IVb) are all greater than 90 � .…”

“…All of these type (II) compounds have molecular skeletons in which the styryl and quinoline units are non-coplanar, as reported here for compounds (IVa)-(IVc). This appears to be the case for all of the 4-styrylquinolines which have been structurally characterized so far, in contrast to the 2-and 8-styrylquinolines, where the two ring systems appear always to be effectively coplanar (Vera et al, 2022;Ardila et al, 2022).…”