Natural source, bioactivity and synthesis of 3-Arylcoumarin derivatives

3-arylcoumarins with different pharmacological properties widely exist in a variety of natural plants. The extensive research on 3-arylcoumarins was attributed to its therapeutic and relatively easy isolation. Therefore, 3-arylcoumarins can be recognised as useful structures for the design of novel compounds with potential pharmacological interest, particularly in the fields of anti-inflammatory, anti-cancer, antioxidant, Monoamine oxidase (MAO) enzyme inhibition, etc. The current review highlights the biological activities, design, and chemical synthetic methods of 3-arylcoumarins derivatives as well as their important natural product sources.

Dual Role of Oxoaldehydes: Divergent Synthesis of 3-Aryl- and 3-Aroylcoumarins

A facile and efficient synthetic approach to various valuable 3-aryl- and 3-aroylcoumarins by the direct arylation and aroylation of coumarins with glyoxals in a metal-free manner is presented. The aryl glyoxal is for the first time recognized to serve as an aryl surrogate in addition to its role as an aroyl transfer reagent via a simple switch in reaction conditions. The approach accommodates a broad substrate scope and high yields of the two types of cross-coupling reactions starting from identical starting materials.

Brønsted acid catalyzed annulations of ketene dithioacetals: synthesis of 3-aryl coumarins and indenes

PTSA catalyzed divergent synthetic routes toward 3-aryl coumarins and indenes were developed using ketene dithioacetals. These transformations are transition-metal and oxidant free, proceed under mild conditions, and provide quick access to these important structural motifs.

3-Phenylcoumarins as a Privileged Scaffold in Medicinal Chemistry: The Landmarks of the Past Decade

3-Phenylcoumarins are a family of heterocyclic molecules that are widely used in both organic and medicinal chemistry. In this overview, research on this scaffold, since 2010, is included and discussed, focusing on aspects related to its natural origin, synthetic procedures and pharmacological applications. This review paper is based on the most relevant literature related to the role of 3-phenylcoumarins in the design of new drug candidates. The references presented in this review have been collected from multiple electronic databases, including SciFinder, Pubmed and Mendeley.

Palladium-Catalyzed Weakly Coordinating Lactone-Directed C-H Bond Functionalization of 3-Arylcoumarins: Synthesis of Bioactive Coumestan Derivatives

A palladium-catalyzed highly regioselective ortho-selective C-H functionalization of 3-arylcoumarins has been developed. The method utilizes the weakly coordinating lactone as a directing group. The versatility of the strategy is highlighted by developing methodologies for alkenylation, halogenation, fluoroalkoxylation, and hydroxylation. Different functional groups were well tolerated, and functionalized coumarins were obtained in moderate to high yields. The method also showed good selectivity for monofunctionalization versus difunctionalization. The generated ortho-hydroxy derivatives were cyclized in the presence of DDQ, thus developing a simple and fast method for the synthesis of bioactive coumestan from 3-arylcoumarins.

Rh-Catalyzed aldehydic C–H alkynylation and annulation

Novel Rh-catalyzed aldehydic C–H bond alkynylation and annulation for the in situ synthesis of chromones and aurones are described.

Chlorophyll-catalyzed photochemical regioselective coumarin C–H arylation with diazonium salts

A metal-free, direct C–H arylation of coumarins with aryl diazonium salts at room temperature using chlorophyll as a green photosensitizer is devised.

Visible-light-driven copper-catalyzed aerobic oxidative cascade cyclization of N-tosylhydrazones and terminal alkynes: regioselective synthesis of 3-arylcoumarins

An intuitive visible-light-driven copper-catalyzed process can accomplish regioselective functionalized 3-arylcoumarins via oxidative annulation of simple N-tosylhydrazones with terminal alkynes under O₂ (1 atm.) at room temperature.

Synthesis of Diversely Functionalized 2 H-Chromenes through Pd-Catalyzed Cascade Reactions of 1,1-Dibromoolefin Derivatives with Arylboronic Acids

In this work, an unprecedented synthesis of (2 H-chromen-2-ylidene)acetates and (2 H-chromen-2-ylidene)ethanones with controlled stereoselectivity via Pd-catalyzed cascade reactions of 3-(2-(2,2-dibromovinyl)phenoxy)acrylates or 3-(2-(2,2-dibromovinyl)phenoxy)enones with aryl boronic acids has been established. This protocol combines two C-C bond forming reactions (an intermolecular Suzuki coupling followed by an intramolecular Heck coupling) in one pot under the catalysis of the same catalyst. Compared with literature methods for the preparation of 2 H-chromene derivatives, it has advantages such as easily obtainable or commercially available substrates, diverse substitution pattern of products, simple procedure, and excellent stereoselectivity. Interestingly, this cascade reaction could distinguish the subtle difference of the electron-withdrawing capacity and the size of various functional groups and thus resulted in a different chemoselectivity. In addition, the utility of the (2 H-chromen-2-ylidene)acetate thus obtained was showcased by its facile transformation into the synthetically and photophysically significant 3 H-xanthen-3-one derivative.

Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides using N-formylsaccharin as a CO surrogate

A highly efficient synthesis of 3-arylcoumarins by Pd-catalysed carbonylative cyclisation of salicylaldehydes with benzyl chlorides using N-formylsaccharin as a CO source is developed.

Elemental sulfur accelerated the reactivity of the 3-position of indole for the construction of chromeno[2,3-b]indoles

Elemental sulfur not only acted as an additional oxidant but also facilitated the reactivity of the 3-position of indole to construct chromeno[2,3-b]indoles.

Practical Synthesis of Chromeno[2,3-b]indole Skeleton via an Aldehyde Group Insertion/Aromatization Strategy

The synthesis of chromeno[2,3-b]indole from simple starting materials remains a demanding process. Herein, 2-bromoindole undergoes nucleophilic attack from salicylaldehyde, followed by intramolecular insertion of an aldehyde group and aromatization to generate the desired chromeno[2,3-b]indoles. Moreover, various functional groups were tolerated and a gram-scale synthesis of the product could be achieved under the optimized condition.

Regioselective C-3 arylation of coumarins with arylhydrazines via radical oxidation by potassium permanganate

An efficient protocol for oxidative C-3 arylation of coumarins with arylhydrazine has been developed using potassium permanganate as an oxidant. The arylated coumarins with different electronic properties were obtained in moderate to good yields. The developed protocol for direct C-3 arylation of coumarins could be extended to quinolinones.

KMnO4/AcOH-mediated C3-selective direct arylation of coumarins with arylboronic acids

An efficient protocol for KMnO₄/AcOH-mediated C3-direct radical arylation of coumarins with arylboronic acids to afford 3-arylcoumarin derivatives is described.

Synthesis of quinazolinimines and quinazolinamines from 2-fluorobenzonitriles under catalyst-free conditions

A convenient procedure for the synthesis of quinazolinimines and quinazolinamines from 2-fluorobenzonitriles and 2-aminopyridines or amidines with KO^tBu as the promotor has been developed.