H5BW12O40-Catalyzed syntheses of 1,4-dihydropyridines and polyhydroquinolines via Hantzsch reaction: Joint experimental and computational studies

Abstract

A series of polyhydroquinoline derivatives were effectively synthesized via Hantzsch reaction in high yields in the presence of catalytic amounts of a highly negatively charged borotungstic acid H5BW12O40 in refluxing EtOH under green and mild reaction conditions. It is a Keggin-type heteropoly acid with a higher negative charge and strong Brønsted acidity. Moreover, a comparative mechanistical analysis of Hantzsch reaction was made based on the structural, thermodynamical and electronic properties along the reaction pathway using density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) approaches.

Preparation, Antibacterial Activity, and Catalytic Application of Magnetic Graphene Oxide‐Fucoidan in the Synthesis of 1,4‐Dihydropyridines and Polyhydroquinolines

“…Thermogravimetric analysis (TGA) was measured by Bahr-STA 504 instrument. The SEM images were carried out using a TESCAN [36] 5a 2 12 92 292-295/ > 220 [37] 5b 3 10 94 289-290/290-292 [38] 5c 4 12 95 298-300/ > 220 [36] 5d 5 15 92 275-278/274-276 [3] 5e 6 15 94 183-185/182-184 [39] 6f 7 16 92 202-204202-204 [40] 6 g 8 14 93 255-257/255-257 [41] 6 h 9 10 96 179-181/180-183 [29] 6i instrument. Elemental analysis of the nanocomposite was done by EDX analysis recorded by TESCAN4992.…”

“…The temperature was increased up to 35 °C . After- 203-204/203-205 [28] 6j 11 14 95 238-241/235-240 [29] 6k 12 15 90 254-256/255-257 [29] 6 l 13 15 96 245-246/244-246 [41] 6 m 14 14 92 225-228/226-228 [42] 6n wards, a brown suspension was obtained by adding slowly 50 ml of water from 35 °C to 98 °C. H 2 O 2 (30 %) and 2 ml of HCl (32 %) were added to the diluted solution, respectively-Finally, the obtained sediment was washed with DI water several times to remove all the acids.…”

“… [25] The classical approach for the synthesis of these compounds is one‐pot condensation reactions of various aldehydes with β‐ketoesters, dimedone, and ammonium acetate under drastic conditions. In recent decades, some improved procedures using an extensive range of catalysts including magnetic chitosan‐terephthaloyl‐creatine, [26] BiFeO 3 , [27] and γ‐Fe 2 O 3 /Cu@cellulose, [28] Keggin‐type heteropolyacid H 5 BW 12 O 40 , [29] and amine‐functionalized graphene oxide nanosheets (AFGONs) [13] have been reported in the literature. While many of them have their merits, some of them have a variety of drawbacks, including harsh reaction conditions, expensive catalysts, and a tedious preparation and work‐up process.…”

Catalytic Approaches to Multicomponent Reactions: A Critical Review and Perspectives on the Roles of Catalysis

“…In the presence of a catalyst, however, it is possible to considerably improve the reaction efficiency (higher yields), as we [ 33 ] and many groups [ 34 , 35 , 36 , 37 , 38 , 39 , 40 ] have already demonstrated, as well as select a preferred reaction pathway and avoid this large number of competing mechanisms. Under optimized catalytic conditions, side reactions can also be avoided or favored [ 41 , 42 ], depending on the interest, as recently demonstrated for the Hantzsch MCR [ 43 ] and for a Hantzsch-like [ 44 ] reaction.…”

Recent Progresses in the Multicomponent Synthesis of Dihydropyridines by Applying Sustainable Catalysts Under Green Conditions

“…Momeni and his colleagues (Momeni et al, 2020) developed a routine to synthesise 1,4-dihydropyridines (100) and polyhydro quinolines (101), employing H 5 BW 12 O 40 as a novel catalyst. They implemented a single-pot Hantzsch reaction mechanism using substituted aldehydes (99), acetoacetic esters (17), and ammonium acetate (7) refluxed using borotungstic acid (H 5 BW 12 O 40 ) as a catalyst.…”