TBHP Promoted Cross-Dehydrogenative coupling (CDC) Reaction: Metal/Additive-Free Synthesis of Chromone-Fused Quinolines

Synthetic Methods for Various Chromeno-fused Heterocycles and their Potential as Antimicrobial Agents

Chromenes are a significant family of heterocyclic chemicals that have a wide range of biological applications, a simple chemical structure, and only mildly undesirable side effects. The synthesis of a wide range of chromene analogs that displayed unexpected behaviors via numerous mechanisms was investigated by a number of different research teams, which led to the discovery of multiple pathways for their synthesis. In addition, different chromene-fused heterocycles exhibit a wide variety of fascinating biological actions, including those that are anticancer, anticonvulsant, antibacterial, anticholinesterase, antituberculosis, and anti-diabetic. In light of this, the purpose of this study is to highlight the many synthesis techniques and antibacterial activity associated with chromene-fused heterocyclic compounds. Moreover, such research can open avenues for exploring other therapeutic applications of these compounds in various disease areas, as their biological activities extend beyond antibacterial effects.

Direct Excitation of Aldehyde to Activate the C(sp2 )-H Bond by Cobaloxime Catalysis toward Fluorenones Synthesis with Hydrogen Evolution

A new way to form fluorenones via the direct excitation of substrates instead of photocatalyst to activate the C(sp² )-H bond under redox-neutral condition is reported. Our design relies on the photoexcited aromatic aldehyde intermediates that can be intercepted by cobaloxime catalyst through single electron transfer for following β-H elimination. The generation of acyl radical and successful interception by a metal catalyst cobaloxime avoid the use of a photocatalyst and stoichiometric external oxidants, affording a series of highly substituted fluorenones, including six-membered ketones, such as xanthone and thioxanthone derivatives in good to excellent yields, and with hydrogen as the only byproduct. This catalytic system features a readily available metal catalyst, mild reaction conditions and broad substrate scope, in which sunlight reaction and scale-up experiments by continuous-flow approach make the new methodology sustainable and amenable for potentially operational procedures.

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.

Catalyst-free and additive-free reactions enabling C-C bond formation: a journey towards a sustainable future

This review focuses on the catalyst- and additive-free C-C bond forming reactions reported mostly from the year 2005 to date. C-C bond forming reactions are highly important as large and complex organic molecules can be derived from simpler ones via these reactions. On the other hand, catalyst- and additive-free reactions are economical, environmentally friendly and less sensitive to air/moisture, allow easy separation of products and are operationally simple. Hence, a large number of research articles have been published in this area. Though a few reviews are available on the catalyst-free organic reactions, most of them were published a few years ago. The current review excludes catalysts as well as additives and is specific to only C-C bond formation. Besides many organic name reactions, catalyst/additive-free C-H functionalizations, coupling reactions and UV-visible-light-promoted reactions are also discussed. Undoubtedly, the contents of this review will motivate readers to do more novel work in this area which will accelerate the journey towards a sustainable future.

Copper-catalyzed cascade reaction: synthesis of pyrimido[4,5-b]quinolinones from 2-chloroquinoline-3-carbonitriles with (aryl)methanamines

Cu-catalyzed cascade reaction of 2-chloroquinoline-3-carbonitriles with benzyl amines using sodium hydroxide in aerobic atmosphere has been developed for the synthesis of pyrimido[4,5-b]quinoline-4-ones.

Synthesis of Chromone-Related Pyrazole Compounds

Chromones, six-membered oxygen heterocycles, and pyrazoles, five-membered two-adjacent-nitrogen-containing heterocycles, represent two important classes of biologically active compounds. Certain derivatives of these scaffolds play an important role in medicinal chemistry and have been extensively used as versatile building blocks in organic synthesis. In this context, we will discuss the most relevant advances on the chemistry that involves both chromone and pyrazole rings. The methods reviewed include the synthesis of chromone-pyrazole dyads, synthesis of chromone-pyrazole-fused compounds, and chromones as starting materials in the synthesis of 3(5)-(2-hydroxyaryl)pyrazoles, among others. This review will cover the literature on the chromone and pyrazole dual chemistry and their outcomes in the 21st century.

Na2S-mediated synthesis of terminal alkynes from gem-dibromoalkenes

The Na₂S-mediated facile synthesis of terminal alkynes from gem-dibromoalkenes, at 20/40 °C under open flask conditions has been developed.

Active methylene compounds (AMCs) controlled facile synthesis of acridine and phenanthridine from morita Baylis–Hillman acetate

We carried out simple and facile syntheses of acridines and phenanthridines from MBH acetates of 2-chloro-quinoline-3-carbaldehyde with active methylene compounds (AMCs).

TBAB-catalyzed cascade reactions: facile synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines via 5-exo-dig cyclization of o-arylalkynylquinoline aldehydes

TBAB-catalyzed cascade reaction condition is developed for the synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines from o-arylalkynylquinoline aldehydes via 5-exo-dig cyclization.