Radical Transformations towards the Synthesis of Quinoline: A Review

Abstract

Quinoline is considered one of the most ubiquitous heterocycles due to its engaging biological activities and synthetic utility over organic transformations. Over the past few decades, numerous reports have been documented in the synthesis of quinolines. The classical methods including, Skraup, Friedlander, Doebner‐von‐Miller, Conrad‐Limpach, Pfitzinger quinoline synthesis, and so forth, these are the well‐known methods to construct principal quinoline scaffold with several advantages and limitations. Recently, radical insertion or catalyzed reactions have emerged as a powerful and efficient tool to construct heterocycles with high atom efficiency and step economy. In this concern, this minireview mainly focused on the developments of Quinoline synthesis via radical reactions. In addition, a brief description of the preparation procedure, reactivity, and mechanisms is also included, where as possible. Respectively, the synthesis of quinolines is classified and summarized based on its reactivity, so it will help the researchers to grab the information in this exploration area, as Quinolines are promising pharmacophores.

Recent investigations into synthesis and pharmacological activities of phenoxy acetamide and its derivatives (chalcone, indole and quinoline) as possible therapeutic candidates

“…Furthermore, several quinoline derivatives have been found to be used as agrochemicals as well as in the processing of dyes, food colorants and pH indicators as well as in the synthesis of other organic substances [176]. Moreover, quinolines and its derivatives can also emerge as potential therapeutic agents in the treatment of cancer, heart failure and inflammatory diseases [177,178]. Also, it represents an attractive class of compounds possessing biological activities such as anti-convulsant [179], analgesic [180], anti-bacterial [181], anti-fungal [182], anti-malarial [183] and so on.…”

Transition‐Metal‐Free Synthesis of Functionalized Quinolines by Direct Conversion of β‐O‐4 Model Compounds

“…As an important class of N-heterocyclic compounds, quinolines constitute one of the most prominent groups of biologically active molecules with broad applications as pharmaceuticals, agrochemicals and functionalized materials. [7] The classic synthetic methods, named after Skraup, [7b, 8] Doebner, [9] Doebner-von Miller, [10] Combes, [11] Camps, [12] Pfitzinger, [13] Nimentowski, [14] and Friedländer [15] are entirely reliant on fossil resources, and most of these routes rely on harsh reaction conditions and multiple steps, leading to low chemoselectivity with relatively poor overall yields. Modified or indirect Friedländer protocols, using an aminoalcohol instead of 2-aminobenzaldehyde derivatives as a starting molecule to bypass the instability of the substrates, provides a straightforward approach for quinoline synthesis in the presence of transition-metal complex catalysts based on Ru, [16] Re, [17] Ir, [18] Cu, [19] Ni, [20] and Mn.…”

Synthesis of multiple quinoline derivatives using novel ionic liquid-based nano-magnetic catalyst (MNPs@SiO2-Pr-AP-tribromide)

“…Quinoline is one of the most important and prominent N-heterocyclic structure that has been considered in a wide range of natural, synthetic, and medicinal compounds [22]. Quinolines have properties such as anti-malarial and anti-SARS-CoV-2 [23], corrosion inhibitor [24], HMG-CoA reductase inhibiting [25], antileishmanial, antitubercular, antitumor [26], antihypertensive [27], antibacterial, anti-asthmatic [28], anti-inflammatory [29], anticancer, antioxidant, OLEDs fabrication [30], antifungal, analgesic [31], anti-HIV [32], anticonvulsant [33], anti-Alzheimer [34], anti-diabetic, and anti-platelet activity [35] (Fig.…”