Indazole Synthesis and Biological Activity

Indazoles are bicyclic heterocycles comprising a fused benzene and pyrazole ring that exhibit a wide spectrum of biological activities. Synthetic access to indazole cores has advanced through classical cyclocondensation of o-halonitroarenes with hydrazine, Cadogan cyclisation of nitroindoles and modern C–H activation strategies that enable direct functionalisation at multiple positions. Cross-coupling reactions and convergent approaches have further diversified substitution patterns, allowing precise installation of pharmaceutically relevant moieties. Emphasis on regioselectivity, process intensification and green chemistry principles has led to scalable, high-yielding routes with minimal waste. Biologically, indazole derivatives serve as antimicrobial, antiviral, anticancer and anti-inflammatory agents, and as ligands for kinase and receptor targets. Structural modifications influence ADMET profiles and binding affinities, while computational methods such as molecular docking and density functional theory guide design. The combination of versatile synthesis and tunable bioactivity underpins the indazole scaffold’s prominence in drug discovery, with emerging examples demonstrating clinical potential and sustainable manufacturing.

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Indazole Synthesis and Biological Activity publication trend

The graph below shows the total number of articles in indazole synthesis and biological activity across all publications each year (not limited to Nature Index journals).

Technical terms

Indazole: A bicyclic heterocycle composed of a benzene ring fused to a pyrazole ring.

Regioselectivity: Preference for bond formation at one position over others in a molecule during a chemical reaction.

Convergent synthesis: A strategy in which separate fragments are prepared independently and then coupled to form the target molecule.

Molecular docking: A computational technique used to predict the preferred orientation of a small molecule when bound to a protein target.

ADMET: An acronym for absorption, distribution, metabolism, excretion and toxicity, describing pharmacokinetic and safety properties of a compound.

References

1. Development of a Manufacturing Process toward the Convergent Synthesis of the COVID-19 Antiviral Ensitrelvir. ACS Central Science (2023).
2. Practical Synthesis of 7-Bromo-4-chloro-1H-indazol-3-amine: An Important Intermediate to Lenacapavir. Molecules (2024).
3. Synthesis molecular docking and DFT studies on novel indazole derivatives. RSC Advances (2024).