2-Chloroquinoline-3-carbaldehyde: A Privileged Scaffold in Drug Design

Abstract:

2-Chloroquinoline-3-carbaldehyde is a compound that has gained much attention as a distinct scaffold in medicinal chemistry because of its wide pharmacological uses. A very useful platform for structural diversity is provided by the quinoline core, which has been substituted by a formyl group at position C-3 and a chloro group at position C-2. The aldehyde functional group acts as a reactive site for the synthesis of various heterocyclic analogs, and the chloro group is responsible for the enhancement of lipophilicity and metabolic stability. Therefore, this scaffold has been used extensively as a key intermediate for the synthesis of thiazolidinones, Schiff bases, hydrazones, azetidinones, chalcones, and other biologically active hybrid molecules. According to recent studies, the 2-chloroquinoline-3-carbaldehyde derivatives have been reported to exhibit various biological activities, such as antibacterial, antitubercular, anticancer, anti-inflammatory, antimalarial, and neuroprotective activities. These compounds act through various mechanisms, such as DNA intercalation, enzyme inhibition, signal pathway modulation, and interaction with key therapeutic targets, to exert their biological effects. The Vilsmeier-Haack reaction, oxidation of analogous alcohols, and condensation reactions have been successfully utilized for the synthesis of structurally diverse derivatives with improved biological properties. Structure-activity relationship (SAR) analysis has shown that electron-withdrawing groups, particularly halogen and nitro substituents, have a significant impact on the enhancement of biological activity, and heterocyclic substitutions improve pharmacokinetic properties. Moreover, the potential of this scaffold in multi-target drug research and rational drug design has already been established by computational studies, including in silico ADME studies and molecular docking. Keeping in view the therapeutic potential and future scope for drug discovery, this article gives a comprehensive review of the recent advancements in the synthesis, structural modification, and biological studies of 2-chloroquinoline-3-carbaldehyde derivatives.