New approaches to the synthesis of selected hydroxyquinolines and their hydroxyquinoline carboxylic acid analogues

• Three hydroxyquinolines have been characterized by X-ray diffraction method.
• The X-ray structure of 5-chloro-8-hydroxy-2-methylquinoline-7-carboxylic acid.
• New approaches to the Skraup synthesis of selected hydroxyquinolines.

New approaches to the synthesis of selected crystalline hydroxyquinolines and their carboxylic acid analogues were elaborated in this paper with the auxiliary of computational and spectroscopic characterization, such as FTIR, NMR and single crystal X-ray measurements. The experimental data were further rationalized based on a DFT calculation method with B3LYP functional, which reflected the impact of electron donating or withdrawing groups on the energy level of HOMO orbitals and the reactivity of the substituted hydroxyquinolines.

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