Indolinones

Indolinones are a family of heterocyclic compounds that consist of a benzene ring fused to a five‑membered lactam ring, giving a bicyclic system. The parent structure is often referred to as indolin-2-one or 2-indolinone, a carbonyl-containing derivative of the indoline framework. Substituents at various positions on the benzene ring or on the lactam nitrogen expand this family into a wide range of indolinone derivatives.

The core feature of indolinones is the fusion of a benzene ring with a γ-lactam ring bearing a carbonyl group, typically at the 2-position. This arrangement imparts conjugation across the system and contributes to the planarity of the core. Many derivatives are generated by functionalizing the 3-position of the indolinone ring, as well as by N-substitution and further substitutions on the benzene ring. These compounds can exist in several tautomeric or resonance forms depending on substitution and oxidation state.

Synthesis and reactivity of indolinones are well developed in organic chemistry. Common routes include cyclization of o-aminophenylacetates or related precursors to form the lactam ring, followed by oxidation or reduction steps to install further functionality. The lactam carbonyl makes the ring susceptible to nucleophilic addition and enables various substitutions, enabling access to diverse libraries of compounds for research and development.

Applications focus on the indolinone scaffold as a versatile platform in medicinal chemistry. Many derivatives exhibit biological activities, including anticancer, antimicrobial, and anti-inflammatory effects. The core is also used as a building block in the synthesis of more complex molecules, including kinase inhibitors and other therapeutic agents.