Indolizine Synthesis and Biological Applications

Indolizines are bicyclic nitrogen heterocycles formed by the fusion of pyrrole and pyridine rings and are valued for their presence in natural products, pharmaceuticals and functional materials. Classical construction of the indolizine core has relied on methods such as Chichibabin synthesis and 1,3-dipolar cycloadditions of pyridinium ylides, but recent advances have introduced more versatile approaches including transition-metal catalysis, organocatalytic annulations and pericyclic electrocyclisations. These modern protocols enable access to diverse substitution patterns and π-expanded analogues under mild or sustainable conditions. Beyond methodology, indolizine derivatives exhibit a broad spectrum of biological activities, notably anticancer, anti-inflammatory and antimicrobial effects, and serve as fluorescent probes for sensing and imaging. The convergence of innovative synthetic strategies with targeted functionalisation has accelerated the translation of indolizine scaffolds into lead compounds and molecular tools with global significance.

Research from Nature Portfolio

Recent studies have demonstrated a recyclable stereoauxiliary aminocatalytic route to trisubstituted indolizine-2-carbaldehydes, using biomass-derived aminosugars to promote a one-pot [3+2] annulation of acyl pyridines and α,β-unsaturated aldehydes in aqueous media. The β-anomeric configuration of D-glucosamine serves as a chiral auxiliary, enhancing selectivity and enabling catalyst recovery on a polymeric chitosan support. This protocol affords a diverse library of functionalised indolizine-2-aldehydes and has been applied to late-stage modification of bioactive molecules. Another development employs a transition-metal-catalysed high-order reaction sequence that combines 8π electrocyclisation of alkenes with metal-carbene-mediated C–H and C–C bond activations to construct novel N-centred perifused cycles. This strategy offers stereo-controlled elaboration of complex heterocycles and demonstrates late-stage modification of pharmaceuticals, highlighting potential for extending indolizine frameworks.

Indolizine Synthesis and Biological Applications publication trend

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

Technical terms

Indolizine: A bicyclic heterocycle comprising fused pyrrole and pyridine rings.

[3+2] annulation: A cycloaddition reaction in which a three-atom component and a two-atom component form a five-membered ring.

Cycloaddition: A pericyclic reaction that joins unsaturated substrates to generate a cyclic product.

Aminocatalysis: Activation of organic substrates by amine catalysts through reversible covalent interactions or hydrogen bonding.

Stereoauxiliary effect: Use of a removable chiral auxiliary to control stereochemical outcomes in a synthetic transformation.

References

1. A recyclable stereoauxiliary aminocatalyzed strategy for one-pot synthesis of indolizine-2-carbaldehydes. Communications Chemistry (2023).
2. Divergent access to 5,6,7-perifused cycles. Nature Communications (2023).
3. Recent advances in the synthesis of indolizines and their π-expanded analogues. Organic & Biomolecular Chemistry (2016).
4. Novel Series of Methyl 3-(Substituted Benzoyl)-7-Substituted-2-Phenylindolizine-1-Carboxylates as Promising Anti-Inflammatory Agents: Molecular Modeling Studies. Biomolecules (2019).
5. A Novel Indolizine Derivative Induces Apoptosis Through the Mitochondria p53 Pathway in HepG2 Cells. Frontiers in Pharmacology (2019).
6. Facile Synthesis of Heterocycles via 2-Picolinium Bromide and Antimicrobial Activities of the Products. Molecules (2008).
7. Fluorescent Indolizine-β-Cyclodextrin Derivatives for the Detection of Volatile Organic Compounds. Sensors (2008).