Synthesis of 3-arylcoumarins through N-heterocyclic carbene catalyzed condensation and annulation of 2-chloro-2-arylacetaldehydes with salicylaldehydes

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.

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.

NHC Pd(II) and Ag(I) Complexes: Synthesis, Structure, and Catalytic Activity in Three Types of C-C Coupling Reactions

Four bis-benzimidazolium salts, 1,4-bis[1'-(N-R-benzimidazoliumyl)methyl]-2,3,5,6-tetramethylbenzene 2X- (L 1 H 2 ·(PF 6 ) 2 : R = ethyl, X = PF6; L 2 H 2 ·Br 2 : R = picolyl, X = Br; L 3 H 2 ·Br 2 : R = benzyl, X = Br; and L 4 H 2 ·Br 2 : R = allyl, X = Br), and their three N-heterocyclic carbene (NHC) Pd(II) and Ag(I) complexes, L 1 Pd 2 Cl 4 (1), L 2 Ag 2 Br 2 (2), and L 4 (AgBr) 2 (3), as well as one anionic complex L 3 H 2 ·(Ag 4 Br 8 ) 0.5 (4), have been synthesized and characterized. Complex 1 adopts a funnel-like type of structure, complex 2 adopts a cyclic structure, and complex 3 is an open structure. In the crystal packing of 1-4, one-dimensional polymeric chains and two-dimensional supramolecular layers are formed via intermolecular weak interactions, including hydrogen bonds, π-π interactions, and C-H···π contacts. The catalytic activities of NHC Pd(II) complex 1 in three types of C-C coupling reactions (Suzuki-Miyaura, Heck-Mizoroki, and Sonogashira reactions) were studied. The results show that this catalytic system is efficient for these C-C coupling reactions.

NHC Hg(ii) and Pd(ii) complexes based on 1,8-dihydroxy-9,10-anthraquinone: synthesis, structure and catalysis

NHC Ag(i) and Hg(ii) complexes were prepared and characterized, and the catalytic activities of the NHC Pd(ii) complex in the Suzuki–Miyaura reaction were investigated.

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.

Synthesis and structural studies of N-heterocyclic carbene Ag(I) and Hg(II) complexes and recognition of dihydrogen phosphate anion

Bis-benzimidazolium salt (S)-2,2'-bis[2″-(N-Et-benzimidazoliumyl)ethoxy]-1,1'-binaphthyl hexafluorophosphate [(S)-L1H2]·(PF6)2 and bis-imidazolium salts (S)-2,2'-bis[2″-(N-R-imidazoliumyl)ethoxy]-1,1'-binaphthyl hexafluorophosphate [(S)-L2H2]·(PF6)2 and [(S)-L3H2]·(PF6)2 (R = ethyl or benzyl), as well as their five N-heterocyclic carbene Hg(II) and Ag(I) complexes such as [(S)-L1Hg(HgBr4)] (1), [(S)-L2Hg(HgBr4)] (2), [(S)-L2Hg(HgI4)] (3), {[(S)-L2Ag](PF6)}n (4) and [(S)-L3Ag](PF6) (5) have been prepared and characterized. Each of complexes 1-3 consists of two rings (one 6-membered ring and one 11-membered ring), in which the oxygen atom in the ligand participates in coordination with Hg(II) ion. In complex 4, 1D helical polymeric chain is formed via biscarbene ligand (S)-L2 and Ag(I) ion. A 15-membered macrometallocycle is constructed through a ligand (S)-L3 and a Ag(I) ion in complex 5. Additionally, the selective recognition of H2PO4- using complex 5 as a receptor was investigated on the basis of fluorescence and UV/vis spectroscopic titrations. The results indicate that complex 5 can distinguish effectively H2PO4- from other anions.

Macrometallocycle binuclear NHC silver(i) complexes: synthesis, structure and recognition of o-phenylenediamine

Macrometallocycle 4 as a host can distinguish o-phenylenediamine from other aromatic amines, which is investigated using the methods of fluorescence and UV/vis spectroscopy.

Enhancement of N-heterocyclic carbenes on rhodium catalyzed olefination of triazoles

A few rhodium complexes of N-heterocyclic carbenes were prepared through carbene transfer reactions and their structures were characterized by X-ray diffraction analysis.

Regioselective α-arylation of coumarins and 2-pyridones with phenylhydrazines under transition-metal-free conditions

A transition-metal-free regioselective α-arylation of coumarins and 2-pyridones has been accomplished by the reaction of phenylhydrazines with coumarins or 2-pyridones.

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, structure and catalysis of a NHC–Pd(ii) complex based on a tetradentate mixed ligand

NHC–Pd(ii) complex 1 has been prepared. The catalytic activity of 1 in C–C coupling reactions was studied.

One-pot synthesis and radical scavenging activity of novel polyhydroxylated 3-arylcoumarins

An unexpected domino rearrangement brought about the development of a novel one-pot procedure for synthesis of coumarins. This protocol allowed the gram-scale synthesis of a variety of polyhydroxylated derivatives 3a-p, from readily available starting materials at a low cost. Based on two proven intermediates, a probable mechanism consisting of boron tribromide induced demethylation/lactone ring opening/elimination/isomerization/lactone ring closure reaction sequence of in situ formed 3-aryl-3,4-dihydroisocoumarin-4-carboxylic acids was deduced. Compared to the common methods, used for the synthesis of coumarins, the proposed herein possesses great advantages, such as mild conditions, good yields for short reaction time, simple work-up procedure and easy isolation of the final products. The structure of the newly synthesized compounds 3a-p was established by spectroscopic methods ((1)H NMR, (13)C NMR, IR, MS and HRMS) and their radical scavenging activity was evaluated in vitro against 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH). The results obtained show that compounds 3g-p posses higher radical scavenging activity (3.16 ≤ SC50 [μM] ≤ 6.82) than well-known antioxidants such as trolox, protocatechuic acid, caffeic acid and gallic acid (SC50 [μM] = 9.34, 8.83, 9.48, 5.33, respectively), which is a precondition for promising antioxidant activity of these compounds to be expected.

Practical organic solvent-free Cu(OAc)2/DMAP/TEMPO-catalyzed aldehyde and imine formation from alcohols under air atmosphere

A highly efficient and practical organic solvent-free Cu(OAc)₂/DMAP/TEMPO catalyst system for the selective aerobic oxidation of benzylic and allylic alcohols to aldehydes and phenones under an ambient air atmosphere was reported.