Synthesis of functionalized chromones via organocatalysis

Divergent Synthesis of 2-Chromonyl-3-hydrazono-chromones and 2-Alkoxy-3-hydrazono-chromones through Switchable Annulation Reactions of o-Hydroxyphenylenaminones with Aryldiazonium Salts

An unprecedented selective chromone annulation reaction controlled by solvent for the divergent synthesis of two types of 2,3-disubstituted chromone skeletons has been developed. A variety of 2-chromonyl-3-hydrazono-chromones and 2-alkoxy-3-hydrazono-chromones were constructed efficiently from readily available o-hydroxyphenylenaminones (o-HPEs) and aryldiazonium salts at room temperature. This strategy is highly chemoselective and features mild reaction conditions, broad substrate scope, broad functional group tolerance, easy gram-scale preparation, and simple filtration to obtain the pure products without tedious column chromatography.

Chromone a Privileged Scaffold in Drug Discovery: Developments on the Synthesis and Bioactivity

Chromones are the class of secondary metabolites broadly occurred in the plant kingdom in a noticeable quantity. This rigid bicyclic system has been categorized "as privileged scaffolds in compounds" in medicinal chemistry. The wide biological responses made them an important moiety in a drug discovery program. This review provides updates on the various methods of synthesis of chromones and biological applications in medicinal chemistry. Various synthetic strategies for the construction of chromones include readily available phenols, salicylic acid and its derivatives, ynones, chalcones, enaminones, chalcones and 2-hydroxyarylalkylketones as starting materials. Synthesis of chromones by using metal, metal free, nanomaterials and different catalysts are included. Details of diverse biological activities such as anti-cancer agents, antimicrobial agents, anti-viral property, anti-inflammatory agents, antioxidants, Monoamine Oxidase-B (MAO-B) Inhibitors, anti-Alzheimer's agents, anti-diabetic agent, antihistaminic potential, antiplatelet agents of chromone derivatives are diecussed.

Electrochemical C-H Halogenations of Enaminones and Electron-Rich Arenes with Sodium Halide (NaX) as Halogen Source for the Synthesis of 3-Halochromones and Haloarenes

Without employing an external oxidant, the simple synthesis of 3-halochromones and various halogenated electron-rich arenes has been realized with electrode oxidation by employing the simplest sodium halide (NaX, X = Cl, Br, I) as halogen source. This electrochemical method is advantageous for the simple and mild room temperature operation, environmental friendliness as well as broad substrate scope in both C-H bond donor and halogen source components.

Rhodium-catalyzed coupling of arenes and fluorinated α-diazo diketones: synthesis of chromones

Rh(iii)-Catalyzed synthesis of chromones using arenes and fluorinated diazo reagents via C–H activation, carbene insertion, and uncatalyzed intramolecular nucleophilic aromatic substitution.

Synthesis of 3-HCF2S-Chromones through Tandem Oxa-Michael Addition and Oxidative Difluoromethylthiolation

A simple protocol for the synthesis of difluoromethylthiolated chromen-4-ones using elemental sulfur and ClCF₂CO₂Na as the difluoromethylthiolating agent is described. Three-component reactions of 2'-hydroxychalcones, ClCF₂CO₂Na, and sulfur under basic conditions using TEMPO as the oxidant afforded HCF₂S-containing 4H-chromen-4-one and 9H-thieno[3,2-b]chromen-9-one derivatives in good yield. The protocol is practical and efficient, and the starting materials are cheap and readily available.

An efficient tandem synthesis of chromones from o-bromoaryl ynones and benzaldehyde oxime

A transition-metal-free approach was developed to synthesize chromones from o-bromoaryl ynones and benzaldehyde oxime by sequential C–O bond formation.

Iridium-Catalyzed and Ligand-Controlled Carbonylative Synthesis of Flavones from Simple Phenols and Internal Alkynes

Flavones are important natural products with diverse biological activities. In this study, a novel procedure for the carbonylative synthesis of flavones has been developed by using simple phenols and internal alkynes as the substrates. Various flavones were isolated in moderate to good yields with excellent regioselectivity and functional group tolerance by using an iridium catalyst system. Notably, this is the first example of direct carbonylative annulation of non-preactivated phenols and alkynes to produce flavones, with the choice of ligand proving to be critical for the success of this transformation.

Facile oxidative cyclization to access C2-quaternary 2-hydroxy-indolin-3-ones: synthetic studies towards matemone

Synergistic oxidation can do it! The precursor for matemone can be facilely prepared in 21% overall yield in 8 steps. The key step is the oxidative cyclization by utilizing CAN and TEMPO to install the quaternary centre.