4-Styrylquinolines from cyclocondensation reactions between (2-aminophenyl)chalcones and 1,3-diketones: crystal structures and regiochemistry

Abstract

Structures are reported for two matched sets of substituted 4-styrylquinolines which were prepared by the formation of the heterocyclic ring in cyclocondensation reactions between 1-(2-aminophenyl)-3-arylprop-2-en-1-ones with 1,3-dicarbonyl compounds. (E)-3-Acetyl-4-[2-(4-methoxyphenyl)ethenyl]-2-methylquinoline, C21H19NO2, (I), (E)-3-acetyl-4-[2-(4-bromophenyl)ethenyl]-2-methylquinoline, C20H16BrNO, (II), and (E)-3-acetyl-2-methyl-4-{2-[4-(trifluoromethyl)phenyl]ethenyl}quinoline, C21H16F3NO, (III), are isomorphous and in each structure the molecules are linked by a single C—H...O hydrogen bond to form C(6) chains. In (I), but not in (II) or (III), this is augmented by a C—H...π(arene) hydrogen bond to form a chain of rings; hence, (I)–(III) are not strictly isostructural. By contrast with (I)–(III), no two of ethyl (E)-4-[2-(4-methoxyphenyl)ethenyl]-2-methylquinoline-3-carboxylate, C22H21NO3, (IV), ethyl (E)-4-[2-(4-bromophenyl)ethenyl]-2-methylquinoline-3-carboxylate, C21H18BrNO2, (V), and ethyl (E)-2-methyl-4-{2-[4-(trifluoromethyl)phenyl]ethenyl}quinoline-3-carboxylate, C22H18F3NO2, (VI), are isomorphous. The molecules of (IV) are linked by a single C—H...O hydrogen bond to form C(13) chains, but cyclic centrosymmetric dimers are formed in both (V) and (VI). The dimer in (V) contains a C—H...π(pyridyl) hydrogen bond, while that in (VI) contains two independent C—H...O hydrogen bonds. Comparisons are made with some related structures, and both the regiochemistry and the mechanism of the heterocyclic ring formation are discussed.

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

“…1-3). These new 2-methylquinoline derivatives (I)-(III) are intended for use as key precursors in the further development of more complex molecules of possible biological value, such as the bis-styrylquinolines (IV) (Scheme 2), (4-styrylquinolin-2-yl)chalcones of the type (V), and the molecular hybrids of types (VI) and (VII), and the work reported here can be regarded as a continuation of an earlier crystallographic study which reported the structures of 2-methyl-4-styrylquinolines having either acetyl or carboethoxy functionalities at position C3 (Rodrı ´guez et al, 2020).…”

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

“…The 4-styrylquinoline precursors of type (I) (see Scheme 1) were prepared using a previously reported method (Mele ´ndez et al, 2020;Rodrı ´guez et al, 2020). In the NMR data listed below, for compounds (III), unprimed ring atoms form part of the quinoline unit, ring atoms carrying a single prime form part of the benzimidazole unit and ring atoms carrying a double prime form part of the styryl unit (see Figs.…”

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

“…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).…”