4‐Styrylquinolines from cyclocondensation reactions between (2‐aminophenyl)chalcones and 1,3‐diketones: crystal structures and regiochemistry |
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Authors: | Diego Rodríguez Sergio Andrs Guerrero Alirio Palma Justo Cobo Christopher Glidewell |
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Institution: | Diego Rodríguez,Sergio Andrés Guerrero,Alirio Palma,Justo Cobo,Christopher Glidewell |
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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. |
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Keywords: | synthesis cyclocondensation quinolone crystal structure molecular conformation hydrogen bonding supramolecular assembly regiochemistry |
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