Crystal structures of four 1-(aryl)-[1,2,4]triazolo[4,3-a]quinoxaline derivatives


The crystal structures of four 1-aryl-[1,2,4]triazolo[4,3-a]quinoxaline derivatives, 2, are reported: [aryl = 3-ClC6H4: 2a; 2-HOC6H4:2b;2,3-(HO)2C6H3: 2c; and 3,4-(MeO)2C6H3: 2d] The compounds, 2, were prepared by oxidation of substituted arenealdehyde quinoxalin-2-ylhydrazones, 1, using ferric chloride in alcohol. In each of the four compounds, the three ring -[1,2,4]triazolo[4,3-a]quinoxaline moiety is a near planar moiety, with all ring atoms within 0.1 Å of the best plane. There are large dihedral angles, 59 ± 7°, between the [1,2,4]triazolo[4,3-a]quinoxaline system and the phenyl ring. The ortho sited hydroxyl groups in 2c are jointly involved in a single Osingle bondH⋯O intramolecular hydrogen bond and individually in Osingle bondH⋯N intermolecular interactions, while the hydroxyl group in 2b is involved in an intermolecular Osingle bondH⋯N hydrogen bond. These and weaker intermolecular interactions, including some of Csingle bondH···Z (Z = O, N and or π) and π···π interactions generate the supramolecular arrangements in 2b and 2c. Intermolecular Csingle bondH···Z (Z = O, N and or π) and π···π interactions are only present in 2a and 2d.

Keywords: [1,2,4]Triazolo[4,3-a]quinoxaline derivatives; Ferric chloride oxidation; Benzaldehyde quinoxalin-2-ylhydrazones; Supramolecular arrangements; Hydrogen bonding; π···π interactions

Document Type: Research Article


Publication date: 15 de Janeiro de 2017

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