Synthesis, Electrochemical and Spectroscopic Characterization of Selected Quinolinecarbaldehydes and Their Schiff Base Derivatives

Abstract

A new approach to the synthesis of selected quinolinecarbaldehydes with carbonyl groups located at C5 and/or in C7 positions is presented in this paper in conjunction with spectroscopic characterization of the products. The classical Reimer-Tiemann, Vilsmeier-Haack and Duff aldehyde synthesis methods were compared due to their importance. Computational studies were carried out to explain the preferred selectivity of the presented formylation transformations. A carbene insertion reaction based on Reimer-Tiemann methodology is presented for making 7-bromo-8-hydroxyquinoline-5-carbaldehyde. Additionally, Duff and Vilsmeier-Haack reactions were used in the double formylation of quinoline derivatives and their analogues benzo[h]quinolin-10-ol, 8-hydroxy-2-methylquinoline-5,7-dicarbaldehyde, 8-(dimethylamino) quinoline-5,7-dicarbaldehyde and 10-hydroxybenzo[h]quinoline-7,9-dicarbaldehyde. Four Schiff base derivatives of 2,6-diisopropylbenzenamine were prepared from selected quinoline-5-carbaldehydes and quinoline-7-carbaldehyde by an efficient synthesis protocol. Their properties have been characterized by a combination of several techniques: MS, HRMS, GC-MS, FTIR, electronic absorption spectroscopy and multinuclear NMR. The electrochemical properties of 8-hydroxy-quinoline-5-carbaldehyde, 6-(dimethylamino)quinoline-5-carbaldehyde and its methylated derivative were investigated, and a strong correlation between the chemical structure and obtained reduction and oxidation potentials was found. The presence of a methyl group facilitates oxidation. In contrast, the reduction potential of methylated compounds was more negative comparing to non-methylated structure. Calculations of frontier molecular orbitals supported the finding. The structures of 8-hydroxy-2-methylquinoline-5,7-dicarbaldehyde and four Schiff bases were determined by single-crystal X-ray diffraction measurements.

Biodegradable Anti-Ultraviolet Film from Modified Gallic Acid Cross-linked Gelatin

“…19 Therefore, one option is to introduce aldehyde groups into the GA structure to increase its reactivity with the amino groups of gelatin, thereby improving the mechanical properties of the cross-linked gelatin film and conferring antioxidant properties. There are many ways to realize the acylation reaction of phenols, including the Vilsmeier−Haack reaction, 20 Reimer−Tiemann reaction, 21 and Duff reaction. 22 Compared with other acylation reactions, the Duff reaction uses phenols as the substrate and acid as the reaction solvent, and the ortho or para positions of phenolic hydroxyl groups can be introduced to aldehyde groups under the action of hexamethylenetetramine (HMTA).…”

New Benzo[h]quinolin-10-ol Derivatives as Co-sensitizers for DSSCs

“…The synthesis of the cyanoacrylic acids 10-hydroxobenzo[ h ]quinoline derivatives ( 1a and 2a ) was carried out by the Knoevenagel condensation reaction of 1 and 2 in the presence of cyanoacetic acid and piperidine. The aldehyde precursors 1 and 2 were prepared according to the previously described procedure [ 42 ].…”

“…All chemicals were commercially available and were used without further purification. 10-Hydroxybenzo[ h ]quinoline-9-carboxaldehyde and 10-hydroxybenzo[ h ]quinoline-7,9-dicarboxaldehyde were synthesized, as has been reported [ 42 ]. The chemicals, instrumental equipment applied for synthesized compounds and solar cells characterization and DSSC preparations are presented in Supplementary Material .…”

Synthesis and Spectroscopic Characterization of Selected Water-Soluble Ligands Based on 1,10-Phenanthroline Core

“…Carbon disulfide (CS 2 ), 2,9-dimethyl-1,10-phenanthroline (neocuproine), 2,4-dihydroxybenzaldehyde, 2-hydroxybenzaldehyde, silver nitrate (AgNO 3 ), t BuLi (1.7 M in pentane), and sodium chlorite (NaClO 2 ) were purchased from Sigma–Aldrich (Poznań, Poland) and were used without further purification. Synthesis of 8-hydroxy-2-methylquinoline-5,7-dicarbaldehyde and 10-hydroxybenzo[ h ]quinoline-7,9-dicarbaldehyde followed our procedure described in the literature [ 39 ].…”