Synthesis of Pentacyclic Pyran Fused Pyrazolo Benzo[h]quinolines by Multicomponent Reaction and Their Photophysical Studies

Abstract

Herein we report for the first time a one-pot method for the synthesis of pentacyclic pyran fused pyrazolo benzo[h]quinolines in acetic acid medium from the threecomponent reaction of 2-hydroxy-1,4-naphthoquinone, α, βunsaturated aldehydes and 5-aminopyrazoles under the reflux conditions. In this reaction, four new bonds (2 CÀ C, 1 CÀ N and 1 CÀ O) and two new rings (pyridine and pyran) were formed in one-pot. The novel products contain four bioactive moieties such as pyran, pyridine, pyrazole and α-naphthol. The salient features of this method are: one-pot process, short reaction time, easier purification, no need of column chromatography and good yields of the products. All the products were characterized by IR, NMR and HRMS. Most of our synthesized compounds were found highly fluorescent. Therefore, we further studied their photophysical properties by UV-Visible and Fluorescence spectroscopy. We have calculated their quantum yields which were found in the range 0.243-0.424 in CHCl 3 solution (c = 10 À 5 M). Compound 4 e showed the highest quantum yield of 0.424.

Multicomponent synthesis of chromophores – The one-pot approach to functional π-systems

“…The catalyst-free three-component reaction of various α,βunsaturated aldehydes, 2-hydroxy-1,4-naphthoquinone and several 5-aminopyrazoles afford pentacyclic pyran-fused pyrazolobenzo[h]quinoline derivatives 100, which incorporate four bioactive components such as pyran, pyridine, pyrazole and α-naphthol (Supplementary Material S35) (Yadav et al, 2022). It is suggested that the α,β-unsaturated aldehyde reacts with 2-hydroxy-SCHEME 18 (A) Silica gel-catalyzed one-pot syntheses of 5-amino-2-aryl-3H-chromeno[4,3,2-de][1,6]naphthyridine-4-carbonitriles 88 and 5-amino-2-aryl-3H-quinolino[4,3,2-de][1,6]naphthyridine-4-carbonitriles 89 (Wu et al, 2010).…”

Synthesis of anthracene linked polycyclic pyridine derivatives fused with coumarin and pyrazole by one‐pot multicomponent strategy followed by oxidation

“…Similar to amino pyrazoles, 4-hydroxycoumarin [24] is also a widely used starting material in MCRs. Considering the usefulness and potent bioactivities of coumarin, pyrazole, dihydropyridine, and pyridine moiety and in the continuity of our research [25], we developed a simple and useful multicomponent reaction of 9-anthracene carboxaldehyde/2-naphthaldehyde, 4-hydroxycoumarin and 3-aminop yrazole using p-toluene sulfonic acid (p-TSA) as a catalyst in acetonitrile. Further oxidation of dihydropyridine to pyridine was done using a catalytic amount of molecular iodine in DMSO (Scheme 1).…”

Catalyst‐free one‐pot synthesis of quinoline tethered α‐amino ketones by multicomponent reactions

“…In this direction multicomponent reactions [16] have received considerable attention due to their operational simplicity, high bond‐forming efficiency, and convergent synthesis. In continuation of our research work on the development of a new methodology [17], herein, we have reported a one‐pot green methodology for the synthesis of quinoline tethered α ‐amino ketones by the three‐component reaction of arylglyoxal, 2‐aminoquinoline, and 4‐hydroxy‐1‐methylquinolin‐2(1 H )‐one/barbituric acid in ethanol under reflux condition (Scheme 1d).…”