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

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Abstract

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 OH⋯O intramolecular hydrogen bond and individually in OH⋯N intermolecular interactions, while the hydroxyl group in 2b is involved in an intermolecular OH⋯N hydrogen bond. These and weaker intermolecular interactions, including some of CH···Z (Z = O, N and or π) and π···π interactions generate the supramolecular arrangements in 2b and 2c. Intermolecular CH···Z (Z = O, N and or π) and π···π interactions are only present in 2a and 2d.

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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 DOI: http://dx.doi.org/10.1016/j.molstruc.2016.09.021 Publication date: 15 de Janeiro de 2017 [:en]

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Abstract

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 OH⋯O intramolecular hydrogen bond and individually in OH⋯N intermolecular interactions, while the hydroxyl group in 2b is involved in an intermolecular OH⋯N hydrogen bond. These and weaker intermolecular interactions, including some of CH···Z (Z = O, N and or π) and π···π interactions generate the supramolecular arrangements in 2b and 2c. Intermolecular CH···Z (Z = O, N and or π) and π···π interactions are only present in 2a and 2d.

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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 DOI: http://dx.doi.org/10.1016/j.molstruc.2016.09.021 Publication date: 15 de Janeiro de 2017 [:]