Iodine-Catalyzed Diversity-Oriented Synthesis of 3,4-Heterocycle-Fused Coumarins from 4-Aminocoumarins and Aurones in Different Solvent

An unprecedented protocol has been developed for the synthesis of 3,4-heterocycle-fused coumarins from 4-aminocoumarins and aurones through iodine-catalyzed cascade reactions. Dihydropyridine-fused coumarin, pyridine-fused coumarin, and pyrrole-fused coumarin derivatives were achieved in good yields with high selectivity when CH3CN, AcOH, and DMSO were used as the solvent, respectively. This protocol provides several advantages, such as easily available starting materials, high atom economy, friendly environment, and simple procedure.

Annulated Heterocyclic[g]Coumarin Composites: Synthetic Approaches and Bioactive Profiling

Coumarins, widely abundant natural heterocyclic compounds, are extensively employed in creating various biologically and pharmacologically potent substances. The hybridization of heterocycles presents a key opportunity to craft innovative multicyclic compounds with enhanced biological activity. Fusing different heterocyclic rings with the coumarin structure presents an intriguing method for crafting fresh hybrid compounds possessing remarkable biological effects. In the pursuit of creating heterocyclic-fused coumarins, a wide range of annulated heterocyclic[g]coumarin composites has been introduced, displaying impressive biological potency. The influence of the linear attachment of heterocyclic rings to the coumarin structure on the biological performance of the resulting compounds has been investigated. This review centers on the synthetic methodologies, structural activity relationship investigation, and biological potentials of annulated heterocyclic[g]coumarin composites. We conducted searches across several databases, including Web of Science, Google Scholar, PubMed, and Scopus. After sieving, we ultimately identified and included 71 pertinent studies published between 2000 and the middle of 2023. This will provide valuable perspectives for medicinal chemists in the prospective design and synthesis of lead compounds with significant therapeutic effects, centered around heterocycle-fused coumarin frameworks.

Synthesis of Chromenopyrroles (Azacoumestans) from Functionalized Enones and Alkyl Isocyanoacetates

Elegant synthetic strategies for chromenopyrroles (azacoumestans) have been devised via cycloaddition of 2-hydroxychalcone/cyclic enones and alkyl isocyanoacetate, followed by lactonization. Herein, ethyl isocyanoacetate acts as a C-NH-C-C═O synthon contrary to its hitherto applications as a C-NH-C synthon. Subsequently, pentacyclic-fused pyrroles were also constructed from the o-iodo benzoyl chromenopyrroles using the Pd(II) catalyst.

Green and Efficient Construction of Chromeno[3,4-c]pyrrole Core via Barton-Zard Reaction from 3-Nitro-2H-chromenes and Ethyl Isocyanoacetate

A regioselective one-pot method for the synthesis of 1-ethyl 2,4-dihydrochromene[3,4-c]pyrroles in 63-94% yields from available 2-phenyl-, 2-trifluoro(trichloro)methyl- or 2-phenyl-2-(trifluoromethyl)-3-nitro-2H-chromenes and ethyl isocyanoacetate through the Barton-Zard reaction in ethanol at reflux for 0.5 h, using K₂CO₃ as a base, has been developed.

Weakly Coordinating tert-Amide-Assisted Ru(II)-Catalyzed Synthesis of Azacoumestans via Migratory Insertion of Quinoid Carbene: Application in the Total Synthesis of Isolamellarins

A weakly coordinating tert-amide-directed straightforward method was developed for the synthesis of azacoumestans using the corresponding azaheterocycle derivatives and diazonaphthoquinones under cheap Ru(II)-catalyzed conditions. The reaction proceeds via migratory insertion of quinoid carbene and subsequent Brønstead acid-mediated cyclization. The optimized C2-selective method offered a wide scope of important azaheterocycles. Bioactive natural products like isolamellarins A and B were synthesized via the developed protocol. Preliminary mechanistic studies highlighted the probable mechanistic pathway.

4-Chloro-3-formylcoumarin as a multifaceted building block for the development of various bio-active substituted and fused coumarin heterocycles: a brief review

This review presents the diverse synthesis of 3,4-substituted coumarins and 5-, 6- and 7-membered ring fused coumarins using 4-chloro-3-formylcoumarin as the precursor via classical reactions including metal-catalyzed and green reaction protocols.