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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.

This report describes the syntheses of three new trans-palladium dichloride complexes of bulky selenium ligands. These complexes possess a Cl?Pd?Cl rotor spoke attached to a Se?Pd?Se axle. The new ligands and palladium complexes (C1?C3) were characterized with the help of NMR, HRMS, UV-Vis., IR, and elemental analysis. The single-crystal structure of metal complex C2 confirmed a square planar geometry of complex with trans-orientation. The X-ray structure revealed intramolecular secondary interactions (SeCH—Cl) between chlorine of PdCl2 and CH2 proton of selenium ligand. Variable-temperature NMR data shows coalescence of diastereotopic protons, which indicates pyramidal inversion of selenium atom at elevated temperature. The relaxed potential energy scan of C2 suggests a rotational barrier of ～12.5 kcal/mol for rotation of chlorine atom through Cl?Pd?Cl rotor. The complex C3 possesses dual intramolecular secondary interactions (OCH2—Cl and SeCH2—Cl) with stator ligand. Molecular rotor C2 was found to be a most efficient catalyst for the decarboxylative Heck-coupling under mild reaction conditions. The protocol is applicable to a broad range of substrates with large functional group tolerance and low catalyst loading (2.5 mol %). The mechanism of decarboxylative Heck-coupling reaction was investigated through experimental and computational studies. Importantly the reaction works under silver-free conditions which reduces the cost of overall protocol. Further, the catalyst also worked for decarboxylative arylation and decarboxylative Suzuki-Miyaura coupling reactions with good yields of the coupled products.

Overproduction of uric acid in the body leads to hyperuricemia, which is also closely related to gout. Uric acid production can be lowered by xanthine oxidase (XO) inhibitors. Inhibition of XO has also been proposed as a mechanism for improving cardiovascular health. Therefore, the search for new efficient XO inhibitors is an interesting topic in drug discovery. 3-Phenylcoumarins and 2-phenylbenzofurans are privileged scaffolds in medicinal chemistry. Their structural similarity makes them interesting molecules for a comparative study. Methoxy and nitro substituents were introduced in both scaffolds. The current study gives some insights into the synthesis and biological activity of these molecules against this important target. For the best compound of the series, the 3-(4-methoxyphenyl)-6-nitrocoumarin (4), the IC50 value, type of inhibition, cytotoxicity on B16F10 cells and ADME theoretical properties, were determined. Docking studies were also performed in order to better understand the interactions of this molecule with the XO binding pocket. This work is a preliminary screening for further design and synthesis of new non-purinergic derivatives as potential compounds involved in the inflammatory suppression, specially related to gout.

This communication describes the development of a mild method for the cross-coupling of the C3-position of coumarin with an array of diazonium salts mediated by chlorophyll as a biocatalyst via visible light catalysis. A natural pigment such as chlorophyll is used as a green photosensitizer and environmentally benign catalyst. This general and easy procedure provides a transition-metal-free alternative for the formation of 3-aryl coumarin derivatives at room temperature with good to excellent yields. This journal is

A new method for selective C-3 alkylation of coumarins using carboxylic acids as alkyl sources is reported. This process offers a practical method for the facile construction of 3-alkyl coumarins with a broad substrate scope. The reaction works under metal-free and aqueous media and both cyclic and acyclic aliphatic carboxylic acids participate in this radical C-C cross coupling reaction.

A highly efficient and straightforward synthesis of diversely substituted coumarins from ynamides and salicylaldehydes in the presence of Zn(II) catalyst has been developed. The sulfonamide moiety of ynamides was successfully recycled in this process, serving as an effective traceless directing group for high regioselectivity in the bond-forming event. The advantages of this protocol are good functional group tolerance, broad substrate scope, simple and high-yielding reaction, recovery/reuse of the sulfonamides, low catalyst loading of inexpensive catalyst, and, by these merits, a more cost-effective and greener process.

We present the first example of sustainable, intuitive, highly regioselective, visible-light-driven copper catalyzed aerobic oxidative cascade cyclization of N-tosylhydrazones with terminal alkynes for the preparation of 3-arylcoumarins at room temperature. This operationally simple methodology has been successfully applied to a wide range of N-tosylhydrazones and alkynes (49 examples), and proceeds well to afford biologically active compounds, such as monoamine oxidase B (MAO-B) inhibitor and horseradish peroxidase (HRP) inhibitor, in satisfactory yields under mild conditions. Furthermore, mechanistic studies suggest that the reaction proceeds via a copper(ii)-superoxo or -peroxo complex mediated oxidative annulation of terminal alkynes, as evidenced by 18O2 isotopic-labelling experiments.

A convenient and highly efficient Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides to afford the corresponding 3-arylcoumarins in good to excellent yields has been developed. Importantly, the protocol utilizes a commercially available, low cost, solid and easy to handle N-formylsaccharin as an alternative to the highly toxic CO gas.

The invention discloses a method for synthesizing a coumarin compound in one step. Starting from simple and easy-to-obtain starting materials, the method disclosed by the invention cost-efficiently and efficiently synthesizes the 3,4-substrituted coumarin compound under mild conditions. With phenol as a material, a phenoxyamide compound is obtained, the phenoxyamide compound, carbon monoxide and alkyne are heated to 45 DEG C to 70 DEG C under normal pressure, so that reaction takes place, and thereby the 3,4-substrituted coumarin compound is obtained in one step. In reaction, an external oxidant does not need to be added, conditions are mild, the reaction yield is high, and the adaptability is good. In case of reaction with asymmetric alkyne, the 3-site and the 4-site of the obtained coumarin compound have unique selectivity.

We present herein the first visible-light-driven hydrocarboxylation as well as carbocarboxylation of alkynes using CO2 via an iridium/cobalt dual catalysis. Such transformations provide access to various pharmaceutically important heterocycles in a one-pot procedure from readily available alkynes. Coumarins, 2-quinolones, and 2-benzoxepinones were directly accessed through a one-pot alkyne hydrocarboxylation/alkene isomerization/cyclization sequence in which the Ir photocatalyst serves a dual role to promote single-electron transfer in alkyne hydrocarboxylation and energy transfer in the subsequent alkene isomerization. Moreover, an unprecedented cobalt carboxylation/acyl migration cascade enables alkyne difunctionalization to introduce γ-hydroxybutenolides with high efficiency. We expect that this cascade strategy will inspire new perspectives for alkyne and alkene difunctionalization.

A one-pot, synthesis of N-arylsulfonyl-2-iminocoumarins is developed at ambient temperature by the reaction of 2-hydroxybenzaldehydes, arylacetonitriles, and aryl sulfonyl chlorides using DABCO as a base in a bio-mass-derived green solvent 2-MethylTHF. A simple telescoped process in which 2H-chromen-2-imines are formed in situ by the condensation of 2-hydroxybenzaldehyde and arylacetonitriles. The formed imines are further reacted with arylsulfonyl chlorides in a one-pot approach to obtain the target compounds. This protocol provides access to 3-aryl-N-arylsulfonyl-2-iminocoumarins in a practical and environmentally benign way avoiding cumbersome steps of intermediate syntheses and purifications.

A highly regioselective and transition-metal free one-pot arylation of chromenones with arylboronic acids has been achieved employing K2S2O8. The procedure consists of a sequence of some reactions including an arylation/decarboxylation cascade and proceeds well in aqueous media to afford biologically interesting flavones and 3-arylcoumarins. This method exhibited excellent selectivity and functional group tolerance under mild conditions. The reaction also showed perfect efficacy for the preparation of styryl coumarins.

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 deve

An Ir photoredox catalyst-mediated highly site-selective direct alkylation and arylation of 2-pyridones has been developed. Under visible-light-promoted conditions, ethyl 2-bromo-2,2-difluoroacetate couples with various 2-pyridones exclusively at the C3 position. A similar photoredox catalysis is also effective for the direct C3- Arylation with diaryliodonium triflates. Thus, these reactions occurs under very mild conditions (blue LEDs irradiation and ambient temperature) to form the corresponding C3- Alkylated and arylated 2-pyridones of potential interest in medicinal and pharmaceutical chemistry.

An ultrasound-assisted one-pot acylation/cyclization reaction between N-acylbenzotriazoles and 2-hydroxybenzaldehydes has been developed for the synthesis of substituted 3-arylcoumarins. Using ultrasound not only allows rapid and clean conversion but also simplifies experimental setup and parallel workup leading to rapid generation of 3-arylcoumarin libraries under mild, solvent-free, and chromatography-free conditions.

An efficient protocol for KMnO4/AcOH-mediated dehydrogenative direct radical arylation of coumarins with arylboronic acids to afford 3-arylcoumarin derivatives is described. A similar reaction system is also applicable to the 3-arylation of quinolinone derivatives. These KMnO4/AcOH-mediated coupling reactions occur regioselectively at the C3 position of coumarins and quinolinones. Some notable features of this method are high efficiency, moderate to good yield, and a broad group tolerance.

The invention discloses 3-aryl coumarin derivatives (I) and (II) and a preparation method thereof and belongs to the field of organic chemistry. According to the method, a substituent coumarin derivative and substituent arylboronic acid are used as raw materials and changed into a solvent with acetic acid under the catalysis of Mn(OAc)3 to synthesize the 3-aryl coumarin derivatives. The synthetic method has the advantages that the raw materials are low in price and easy to get, reaction conditions are mild, the yield is high, operation is convenient, and industrial production is facilitated. The derivatives have potential application in the fields of materials, chemical industry, medicine and the like. A new way is provided for synthesis of the 3-aryl coumarin derivatives. (Please see the description for the formulas I and II).

A facile regioselective metal-free direct α-arylation of coumarins and 2-pyridones is achieved by the reaction of coumarins and 2-pyridones with phenylhydrazine in good yields. The reaction proceeds at room temperature under mild conditions using inexpensive reagents and without the need for step intensive activating groups. The methodology is operationally simple, practically viable and also allows the coupling of similar nitrogen heterocycle aza-coumarins without prerequisite N-protection.

A series of coumarin-resveratrol hybrids, 3-arylcoumarin derivatives 3a-u, were synthesized through the intermolecular condensation reaction of various salicylaldehydes and phenylacetic acids in the presence of 1,4-diazabicyclo[2.2.2]octane under solvent-free conditions. All the synthesized compounds were screened for their inhibitory potency against soybean 15-lipoxygenase. Among them, three compounds (3c, 3j, and 3q) showed good enzyme-inhibitory activities. GRAPHICAL ABSTRACT.

In this manuscript we report the synthesis, pharmacological evaluation and docking studies of a selected series of 3-aryl and 3-heteroarylcoumarins with the aim of finding structural features for the tyrosinase inhibitory activity. The synthesized compounds were evaluated as mushroom tyrosinase inhibitors. Compound 12b showed the lowest IC50(0.19 μM) of the series, being approximately 100 times more active than kojic acid, used as a reference compound. The kinetic studies of tyrosinase inhibition revealed that 12b acts as a competitive inhibitor of mushroom tyrosinase with l-DOPA as the substrate. Furthermore, the absence of cytotoxicity in B16F10 melanoma cells was determined for this compound. The antioxidant profile of all the derivatives was evaluated by measuring radical scavenging capacity (ABTS and DPPH assays). Docking experiments were carried out on mushroom tyrosinase structures to better understand the structure-activity relationships.

A new nickel ferrite nano-crystal-catalyzed, ligand-free strategy for the construction of C-N, C-O, and C-C bonds is presented, in which easily available nitrogen and oxygen nucleophiles, aryl/heteroaryl halides and arylboronic acids are used for the cross-coupling reactions. The reactions can be performed at low catalyst loadings with excellent functional group tolerance and chemoselectivity. A variety of functional groups are compatible with the reaction conditions, including nitro, methoxy, as well as acid- and base-sensitive heteroaromatic groups. This unprecedented chemistry nicely complements classical methods for the N-arylation of amines/heteroamines, the O-arylation of phenols/hydroxycoumarins and biaryl/heteroaryl synthesis. The low cost, easy to handle nature and the simplicity of this catalytic system render the method competitive with comparable copper- and palladium-based protocols which require the presence of sophisticated ligands. Nickel ferrite magnetic nanoparticles were prepared by a simple hydrothermal method and characterized by using XRD, TEM image, energy dispersive X-ray analysis, XPS and FT-IR. The easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economic. The catalyst was reused for five cycles with almost unaltered catalytic activity.

Chronic inflammation is the persistent and excessive immune response and can lead to a variety of diseases. Aiming to discover new compounds with anti-inflammatory activity, we report herein the synthesis and biological evaluation of 3-arylcoumarins. Thirty five 3-arylcoumarins were prepared through Perkin condensation and further acid-promoted hydrolysis if necessary. In lipopolysaccharide-activated mouse macrophage RAW264.7 cells, 6,8-dichloro-3-(2-methoxyphenyl)coumarin (16) and 6-bromo-8-methoxy-3-(3-methoxyphenyl)coumarin (25) exhibited nitric oxide production inhibitory activity with the IC50 values of 8.5 μM and 6.9 μM, respectively, providing a pharmacological potential as anti-inflammatory agents.

The design, synthesis, pharmacological evaluation, and theoretical studies of a new series of halogenated 3-arylcoumarins were carried out with the aim of finding new structural and biological features. This series displays several alkyl, hydroxy, halogen, and/or alkoxy groups in both benzene rings of the 3-arylcoumarin scaffold. Most of the compounds studied show high affinity and selectivity for the human monoamine oxidase B (hMAO-B) isoenzyme, with IC 50 values in the low nanomolar and picomolar range. Most of the evaluated compounds display higher MAO-B inhibitory activity and selectivity than selegiline (the reference compound). Coumarin 12 (3-(3-bromophenyl)-6- methylcoumarin) is the most active compound (IC50=134 pM), being 140-fold more active than selegiline and showing the highest specificity for hMAO-B. To better understand the structure-activity relationships, docking experiments were carried out on human monoamine oxidase (A and B) structures. Finally, the prediction of passive blood-brain partitioning, based on in silico derived physicochemical descriptors, was performed. Coumarins crossing the barrier: The design and synthesis of a new series of halogenated 3-arylcoumarins are described. Monoamine oxidase A and B in vitro inhibition studies, in silico prediction of passive blood-brain partitioning, and docking calculations showed most of the 3-arylcoumarin compounds to be potent and selective.

Controlling reaction selectivity is an eternal pursuit for chemists working in chemical synthesis. As part of this endeavor, our group has been exploring the possibility of constructing different natural product skeletons from the same simple starting mat

Facile synthesis of coumarin via the tandem reaction of salicylaldehyde with aryl-substituted 1,1-dibromo-1-alkene was developed. This new protocol proceeds smoothly under mild and transition-metal-free conditions, it allows rapid access to coumarins containing various heteroatoms that are more difficult to prepare by traditional methods. Based on the isolated intermediate of 4-(diethylamino)-3-phenylchroman-2-one and detailed mechanistic studies, a credible tandem pathway was proposed.

The room-temperature oxidative C-H/C-H cross-couplings between (hetero)arenes and alkenes, coumarins or quinones have been reported by using a highly electrophilic palladium species [Pd(TFA)2], generated in situ from Pd(OAc)2and TFA, as the catalyst and cheap (NH4)2S2O8as the oxidant under air.

Objectives In the present communication, we report the synthesis, pharmacological evaluation, theoretical evaluation of absorption, distribution, metabolism and excretion properties and structure-activity relationship study of a selected series of 3-arylcoumarins (compounds 1-9). Adenosine receptors (ARs) binding activity and selectivity of the synthesized compounds 1-9 were evaluated in this study. Different substituents were introduced in both benzene rings of the evaluated scaffold, at positions 6 and 3′ or 4′ of the moiety. The lack of data on the 3-arylcoumarin scaffold encouraged us to explore the ARs' binding activity of a selected series of derivatives. Methods A new series of coumarins (compounds 1-9) were synthesized and evaluated by radioligand binding studies towards ARs. Key findings Analysing the experimental data, it can be observed that neither the simple 3-arylcoumarin nor the 4′-nitro derivatives presented detectable binding affinity for the evaluated receptors, although most of the other substituted derivatives have good binding affinity profiles, especially against the hA1/hA 3 or only hA3 AR. Conclusions The most remarkable derivative is compound 2, presenting the best affinity for hA3 AR (Ki = 2680 nM) and significant selectivity for this subtype. Graphical Abstract In the present communication, we report the synthesis, pharmacological evaluation, theoretical evaluation of ADME properties and SAR study of a selected series of 3-arylcoumarins (compounds 1-9). Adenosine receptors binding activity and selectivity of the synthesized compounds 1-9 were evaluated in this study, and most of the substituted derivatives have good binding affinity profiles, especially against the hA1/hA3 or only hA3 AR. The most remarkable derivative is compound 2, presenting the best affinity for hA3 AR (Ki = 2680 nM) and significant selectivity for this subtype.

A new regioselective α-arylation of coumarins with unactivated simple arenes via a palladium-catalyzed twofold C-H functionalization is devised. This method offers an attractive new approach to synthesis of a wide variety of 3-arylcoumarins from readily accessible starting materials. This journal is The Royal Society of Chemistry 2013.

A novel regioselective α-arylation of coumarins with readily available arenesulfonyl chlorides and sodium arenesulfinates via palladium-catalyzed direct C-H functionalizations under mild reaction conditions is described. This protocol presents an unexpected and highly regio-controlled arylation of coumarins at C-3 to construct interesting 3-arylcoumarins with fascinating biological and fluorescent properties. The regioselectivity observed is in sharp contrast with that expected for the Heck reactions. Copyright

Cute CO! An interesting and straightforward procedure for the carbonylative synthesis of chromenones from readily available salicylic aldehydes and benzyl chlorides has been developed (see scheme; DPPP=1,3-bis(diphenylphosphino) propane). In the presence of a palladium catalyst, various coumarins were produced in good to excellent yields. Copyright

The condensation reaction of 2-chloro-2-arylacetaldehyde with salicylaldehyde catalyzed by N-heterocyclic carbene (NHC) leading to 3-arylcoumarin was studied. A number of 3-arylcoumarin derivatives were obtained in good to excellent yields via this umpolung reaction. This reaction is facile and experimentally simple and mild.

An unprecedented catalytic asymmetric protonation of ketene dithioacetals is described. Various racemic α-aryl hydrocoumarin derivatives are transformed into enantioenriched dithioacetal-protected hydrocoumarins in the presence of a chiral Br?nsted acid catalyst. A newly developed phosphoric acid, featuring the 3,5-bis(pentafluorothio)phenyl (3,5-(SF5) 2C6H3) substituent, is introduced. The obtained products can be easily converted into either hydrocoumarins or the corresponding chromans via simple hydrolysis or hydrogenation, respectively.

An efficient and general protocol for a rapid synthesis of different substituted 3-aryl coumarins is reported. A series of different substituted phenyl acetic acids have been successfully reacted with different substituted 2-hydroxy benzaldehydes in the presence of cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) and N-methyl morpholine to afford 3-aryl coumarins in good to excellent yields. Georg Thieme Verlag Stuttgart · New York.

We have synthesized fourteen 3-phenylcoumarin derivatives and evaluated their anti-HIV activity. Antiviral activity was assessed on MT-2 cells infected with viral clones carrying the luciferase gene as reporter. Inhibition of HIV transcription and Tat function were tested on cells stably transfected with the HIV-LTR and Tat protein. Six compounds displayed NF-κB inhibition, four resulted Tat antagonists and three of them showed both activities. Three compounds inhibited HIV replication with IC50 values 25 μM. The antiviral effect of the 4-hydroxycoumarin derivative 19 correlates with its specific inhibition of Tat functions, while compound 8, 3-(2-chlorophenyl) coumarin, seems to act through a mechanism unrelated to the molecular targets considered in this research.

An efficient method for the C4-regiocontrolled C-H functionalization of coumarins to enable facile oxidative cross-couplings with simple arene components is disclosed.

A straightforward and atom-economical base-free palladium-catalyzed regioselective direct arylation of coumarins and chromenones is devised. This protocol is compatible with a wide variety of electron-donating and -withdrawing substituents and allows construction of various biologically important flavone and neoflavone backbones.

A convenient and innovative protocol for an efficient synthesis of different substituted 3-arylcoumarins is reported. The developed synthetic route involves a Pd-catalyzed cross-coupling reaction using a catalytic complex Pd-salen. Under these conditions a series of different substituted boronic acids have been successfully coupled to a coumarin halide to afford novel coumarins in good yields.

An expeditious one-pot procedure for the synthesis of substituted coumarins under microwave irradiation is accounted. The method describes an easy and fast method for the synthesis of substituted acetoxy coumarins which are very good fluorophores for medical as well as industrial applications. It makes use of easily available reagents such as triethylamine and acetic anhydride as catalyst. The method finds good applications for the synthesis of multisubstituted coumarins.

ortho-Quinone methides, arising from a formal [2+2] cycloaddition between arynes and DMF, were found to facilely undergo a [4+2] cycloaddition with ester enolates or ketenimine anions to produce diverse coumarins in a straightforward manner. The Royal Society of Chemistry 2011.

A particularly useful, easy, and concise synthesis of diversified 3-aryl coumarin was achieved using Heck coupling reactions between coumarin and aryliodides. The introduction of the aryl moiety occurred regioselective at the 3-position of the heteroaromatic ring. Georg Thieme Verlag Stuttgart - New YorK.

The intramolecular cyclization of the esters of salicylaldehyde, O-hydroxyacetophenones, methyl salicylate, and 2'-hydroxy chalcones by potassium hydroxide in pyridine leads to a short and convenient synthesis of 3,4-disubstituted coumarins. Twenty 3-phenyl coumarins were synthesized in 80-90% yields. No other by-product, such as 2-benzylchromone or-diketones, was observed the reactions. The mild reaction condition involves the removal of more acidic benzylic proton, which leads to a relatively cheap, nontoxic, metal-free method for the synthesis of 3-aryl-4-substituted coumarins. Copyrigh

In the present work an array of novel substituted 2H-chromen-2-one (coumarin) derivatives has been subjected to photophysical analysis. Though the influence of the electron-donating groups such as amino, substituted amino, hydroxyl, alkoxy groups, etc. at position 7 of the coumarin ring system has been extensively studied, the luminescent properties of the coumarin moieties with an acetoxy substituent have not been explored. Herein it is attempted to study the variation of fluorescence behavior of substituted coumarin derivatives with change of nature and position of the substituents on the 2H-chromen-2-one skeleton. Effect of a methyl substituent at position 4 which imposes abnormal photophysical behavior to the chromenone unit has also been briefly described.

Twenty hydroxylated and acetoxylated 3-phenylcoumarins were synthesized, and the structure-activity relationships were investigated by evaluating the ability of these compounds to modulate horseradish peroxidase (HRP) catalytic activity and comparing the results to four flavonoids (quercetin, myricetin, kaempferol and galangin), previously reported as HRP inhibitors. It was observed that 3-phenylcoumarins bearing a catechol group were as active as quercetin and myricetin, which also show this substituent in the B-ring. The presence of 6,2′-dihydroxy group or 6,7,3′,4′-tetraacetoxy group in the 3-phenylcoumarin structure also contributed to a significant inhibitory effect on the HRP activity. The catechol-containing 3-phenylcoumarin derivatives also showed free radical scavenger activity. Molecular modeling studies by docking suggested that interactions between the heme group in the HRP active site and the catechol group linked to the flavonoid B-ring or to the 3-phenyl coumarin ring are important to inhibit enzyme catalytic activity.

3-Substituted coumarins are formed in 37-63% yields by the reaction of 2-(acyloxy)arylaldehydes with the TiC4/R3N reagent system. The structure of the compound 2c was determined by single crystal X-ray analysis.

Present invention refers to substituted cumarines that are capable to emit fluorescent light when iluminated by wave lengths within ultraviolet range. Present invention also refers to process of production of said substtituted cumarines, well as provides compositions containing said substituted cumarines, especially compositions containing said cumarines and volatile solvents and/or adjuvants. Said compositions can be used in objects of great value for its owner, in view of facilitating the identification of such objects.

The reaction mechanism of chemical conversion of (E)-β-[2-hydroxylphenylethylene]benzeneethanol into 2-phenylbenzofuran by DDQ, which involves loss of one carbon unit, was characterized and described. Five naturally occurring 2-phenylbenzofurans of not only the isoflavonoid but also stilbenoid origin were synthesized by use of this chemical scheme, which proved that this new scheme is a useful tool for quick synthesis of 2-phenylbenzofurans.

The Mukaiyama's esterification protocol, using 2-chloro-1-methylpyridinium iodide-triethylamine reagent, has been successfully exploited to provide rapid access to a variety of 3-substituted coumarins in satisfactory yields.

(Equation Presented) New anionic oxygen to α- and β-vinyl carbamoyl migration reactions, 17a and 26a-c → 18 and 30a-c, proceed under LDA-mediated conditions leading stereoselectively to highly substituted stilbenes bearing electron-donating and -withdrawing substituants. Compounds 17a and 26a-c are prepared by combination of efficient, directed ortho metalation, Sonogashira, and Suzuki-Miyaura cross-coupling procedures.

o-Iodophenols and o-iodoaniline derivatives react with terminal alkynes under 1 atm of CO in the presence of pyridine and catalytic amounts of Pd(OAc)2 to generate coumarins and 2-quinolones, respectively, as the only products. Terminal alkynes bearing alkyl, aryl, silyl, hydroxyl, ester and cyano substituents are effective in these processes affording the desired products in moderate yields. The formation of coumarins and 2-quinolones in this process is in stark contrast with all previously described palladium-catalyzed reactions of o-iodophenols or o-iodoanilines with terminal alkynes and CO, which have afforded chromones and 4-quinolones. Moreover, under our reaction conditions terminal alkynes insert into the carbon-palladium bond instead of undergoing a Sonogashira-type coupling as confirmed by an isotope labeling experiment.

Thermal condensation of 2′-hydroxyacetophenones 1a-e with phenylacetic acid 2a in refluxing diphenyl ether gives 4-methyl-3-phenylcoumarins 3a-e. Similarly, reaction of 2-hydroxybenzaldehydes 1f-m and 2-hydroxybenzo-phenones 1n-p with phenylacetic acids 2a-d gives the corresponding 3-arylcoumarins 3f-m and 3-aryl-4-phenylcoumarins 3n-p respectively. Formation of esters 4 and 5 and benzofuran 6 is also observed.