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Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State

1
Department of Chemistry, College of Science, Engineering and Technology, University of South Africa, Private Bag X06, Florida 1710, South Africa
2
Department of Chemistry, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(6), 277; https://doi.org/10.3390/cryst9060277
Received: 9 April 2019 / Revised: 8 May 2019 / Accepted: 10 May 2019 / Published: 28 May 2019
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Abstract

The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated direct one-pot sequential sulfuric acid-mediated ring opening and aryl migration to afford the corresponding 3-arylquinolin-4(1H)-ones (azaisoflavones). View Full-Text
Keywords: trans-2-amino-3,5-dibromochalcone epoxides; NMR spectroscopy; XRD; DFT; 3-arylquinolin-4(1H)-ones trans-2-amino-3,5-dibromochalcone epoxides; NMR spectroscopy; XRD; DFT; 3-arylquinolin-4(1H)-ones
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Mphahlele, M.J.; Maluleka, M.M.; Mampa, R.M. Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State. Crystals 2019, 9, 277.

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