1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

Abstract

This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review.

Electrocatalytic Multicomponent Transformation of Aldehyde, 5‐Amino‐3‐methyl‐1‐phenylpyrazole and Dimedone: An Efficient Protocol for Substituted Pyrazolo[3,4‐b]quinolines

“…In consideration of the above potential application prospects of pyrazolo[3,4‐ b ]quinoline derivatives, their synthesis is always a research hotspot in organic synthetic chemistry. In the reported literatures, the most common synthesis method is the condensation of aldehydes with 1,3‐dicarbonyl compounds and aminopyrazole in organic solvents [9] . So far, FeNi 3 ‐ILs, [10] PEGOSO 3 H, [11] L‐proline, [12] InCl 3 , [13] PEG‐400, [14] AgNPs, [15] triethanolamine lactate ionic liquid/Fe 3 O 4 , [16] and pyridine‐2‐carboxylic acid [17] have been employed as catalysts to promote the reaction successfully.…”

“…In the reported literatures, the most common synthesis method is the condensation of aldehydes with 1,3-dicarbonyl compounds and aminopyrazole in organic solvents. [9] So far, FeNi 3 -ILs, [10] PEGOSO 3 H, [11] L-proline, [12] InCl 3 , [13] PEG-400, [14] AgNPs, [15] triethanolamine lactate ionic liquid/Fe 3 O 4 , [16] and pyridine-2-carboxylic acid [17] have been employed as catalysts to promote the reaction successfully. However, these procedures often require longer reaction times and higher reaction temperatures.…”

Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo[3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed?

“…The 1H-pyrazolo [3,4-b]quinoline, which is the focus of the research in the current publication, can also be obtained using multi-component reactions. Only some of these will be mentioned, because an exhaustive discussion of this topic was made in our recent review [9]. The first reaction of this kind was described in 1998 by Hormanza et al (Scheme 1) [10].…”

Dimethyl Sulfoxide-Assisted, Iodine- and Ascorbic Acid-Catalyzed One-Pot Synthetic Approach for Constructing Highly Substituted Pyrazolo[1,5-a]quinoline Thioether Derivatives

“…Pyrazolo­[1,5- a ]­quinoline 22 was previously synthesized by various methods such as the S N Ar/Dieckmann Thorpe cyclization cascade reaction, , annulation of arylpyrrole through visible light, heterocyclization of enaminones by tandem amine exchange, and vinylogous nitroaldol conversion and N-arylation catalyzed by copper . Pyrazoloisoquinoline, a similarly comparable structural motif of pyrazoloquinoline, has also attracted interest, and various methods have been published . It continues a significant provocation to originate a simple approach to achieve benzannulation along with arylsulfenylation subject to the following situations: (a) accompanied by a considerable substrate scope using a commercial precursor, (b) without using the precious metals and ligands, (c) without any toxic compounds, and (d) under mild reaction conditions.…”