- A novel NHC-catalyzed transformation of 2H-chromene-3-carboxaldehydes to 3-methyl-2H-chromen-2-ones
-
An unexpected transformation of 2H-chromene-3-carboxaldehydes to coumarin derivatives, mediated by NHC, is reported.
- Nair, Vijay,Sinu,Rejithamol,Seetha Lakshmi,Suresh, Eringathodi
-
-
Read Online
- Efficient synthesis of 3-methyl-2H-chromen-2-one: Classic versus microwave conditions
-
The reaction of salicylaldehyde with propionic anhydride in the presence of anhydrous K2CO3 as catalyst afforded 3-methyl-2H-chromen- 2-one (3-methylcoumarin) in good yields depending on the reaction conditions. The reaction was performed under classic thermal (55% yield) and microwave conditions (91-97% yield).
- Florekova, Lenka,Flasik, Radoslav,Stankovicova, Henrieta,Gaplovsky, Anton
-
-
Read Online
- Copper(I)-Catalyzed 3-Position Methylation of Coumarins by Using Di-tert-butyl Peroxide as the Methylation Reagents
-
The copper-catalyzed methylation of coumarin by using di-tert-butyl peroxide (DTBP) has been described. The reaction provides direct access to a wide range of 3-methylcoumarins in moderate to good yields. In this procedure, it is noteworthy that DTBP was employed not only as the oxidant, but also as the methyl source. The copper-catalyzed methylation of coumarin by using di-tert-butyl peroxide (DTBP) has been described. The reaction provides direct access to a wide range of 3-methylcoumarins in moderate to good yields. In this procedure, it is noteworthy that DTBP was employed not only as the oxidant, but also as the methyl source.
- Zhuang, Huan,Zeng, Runsheng,Zou, Jianping
-
-
Read Online
- Facile Synthesis of 3-Methyl-5,6-dihydro-2H-pyran-2-ones and 3-Methylcoumarines under Mild Conditions
-
The synthesis of the 3-methyl-5,6-dihydro-2H-pyran-2-one, 3, 5 and the 3-methylcoumarines 7a-e from the β-hydroxyoxo compounds 1,4,6a-c and the phosphonopropionic acid 2 under Wittig-Horner conditions is described.
- Falsone, Gioacchino,Spur, Bernd,Wingen, Peter H.
-
-
Read Online
- Exploring Pd/Al2O3 Catalysed Redox Isomerisation of Allyl Alcohol as a Platform to Create Structural Diversity
-
Abstract: We report our results on exploiting the different reactivities present in the catalytic cycle of the Pd/Al2O3 catalyzed redox isomerization of allyl alcohol. We show that the reactivity of allyl alcohol derived acrolein and enol can be involved in further cascade reactions leading to a diverse set of products. While the oxidation product acrolein can react via Michael and oxa-Michael reactions, the isomerization product enol can be readily involved in aldol condensation processes. Salicylaldehydes, that are able to react on their electrophilic carbonyl and nucleophilic OH-groups with allyl alcohol derived enol and acrolein, respectively, are used to explore conditions where the structure of the product heterocycles can be controlled. Graphical Abstract: [Figure not available: see fulltext.].
- Dékány, Attila,Lázár, Enik?,Szabó, Bálint,Havasi, Viktor,Halasi, Gyula,Sápi, András,Kukovecz, ákos,Kónya, Zoltán,Sz?ri, Kornél,London, Gábor
-
-
Read Online
- Novel one-pot asymmetric cascade approach toward densely substituted enantioenriched α-methylene-γ-lactams
-
A novel one-pot asymmetric synthesis of densely substituted α-methylene-γ-lactams in favor of cis-isomer involving Zn-promoted aza-Barbier-type reaction has been well established. A wide array of α-methylene-γ-lactams were obtained in high yields with excellent diastereomeric ratios from 98:2 to >99:1 and good enantioselectivities. The synthetic potential of such α-methylene-γ-lactams was demonstrated by successfully oxidizing the phenol moiety to quinone in quantitative yield.
- Tan, Yu,Yang, Xiao-Di,Liu, Wen-Jie,Sun, Xing-Wen
-
-
Read Online
- Synthesis and properties of a new coumarin functionalized tetrathiafulvalene derivative
-
Anew tetrathiafulvalene (TTF) derivative possessing Schiff base core with the coumarin moiety has been synthesized and characterized. The crystal structure has been studied, and the electrochemical and spectroscopic properties have also been investigated. Optimized conformation and molecular orbital diagram of the title compound have been calculated with density functional theory (DFT).
- Hu, Liang,Zhu, Rong-Mei,Qin, Jie,Zhou, Xin-Hui
-
-
Read Online
- Visible-Light-Induced C(sp2)-C(sp3) Coupling Reaction for the Regioselective Synthesis of 3-Functionalized Coumarins
-
A photocatalysis strategy for the regioselective synthesis of 3-functionalized coumarins is reported. With visible light irradiation, a direct and regioselective C(sp2)-C(sp3) coupling reaction of 3-(2-hydroxyphenyl)acrylates with ethers or thioethers occurs by using Ru(bpy)3Cl2·6H2O as a photocatalyst and TBHP as an oxidant. The cascade process involves alkenylation of the C(sp3)-H bond of ethers and lactonization, furnishing 3-alkylated coumarins as the final products. This approach is characterized by a broad substrate scope, mild reaction conditions, and simplified operation. The synthesis of 3-alkylated coumarins could be realized by a one-pot procedure, starting from commercially available salicylaldehyde.
- Li, Hanjie,Lin, Zhenwei,Lu, Ping,Qiao, Li,Wang, Yanguang,Xie, Jianwei,Zhang, Ke
-
p. 9552 - 9562
(2021/07/26)
-
- Visible-light promoted oxidative cyclization of cinnamic acid derivatives using xanthone as the photocatalyst
-
We have developed an efficient photocatalytic synthesis of coumarin derivativesviaa tandem double bond isomerization/oxidative cyclization of cinnamic acids. Inexpensive and stable xanthone was used as the photocatalyst, and readily available Selectfluor was used as the oxidant. This method tolerates a wide range of functional groups and offers excellent chemical yields in general. Besides, the photocatalytic oxidative cyclization of cinnamic acid esters gives dimerized lignan-type products.
- Zhao, Bin,Xu, Bo
-
supporting information
p. 568 - 573
(2021/02/06)
-
- Coumarins by Direct Annulation: β-Borylacrylates as Ambiphilic C3-Synthons
-
Modular β-borylacrylates have been validated as programmable, ambiphilic C3-synthons in the cascade annulation of 2-halo-phenol derivatives to generate structurally and electronically diverse coumarins. Key to this [3+3] disconnection is the BPin unit which serves a dual purpose as both a traceless linker for C(sp2)–C(sp2) coupling, and as a chromophore extension to enable inversion of the alkene geometry via selective energy transfer catalysis. Mild isomerisation is a pre-condition to access 3-substituted coumarins and provides a handle for divergence. The method is showcased in the synthesis of representative natural products that contain this venerable chemotype. Facile entry into π-expanded estrone derivatives modified at the A-ring is disclosed to demonstrate the potential of the method in bioassay development or in drug repurposing.
- Wienhold, Max,Molloy, John J.,Daniliuc, Constantin G.,Gilmour, Ryan
-
supporting information
p. 685 - 689
(2020/11/30)
-
- Facile one-pot synthetic access to libraries of diversely substituted 3-aryl (Alkyl)-coumarins using ionic liquid (IL) or conventional base/solvent, and an IL-mediated approach to novel coumarin-bearing diaryl-ethynes
-
The in-situ formed carbonylimidazole derivatives of Ar(alkyl)-CH2COOH react at r.t. with substituted salicylaldehydes in [BMIM][PF6] or [BMIM][BF4] as solvent, and [PAIM][NTf2] as basic-IL, to produce libraries of 3-aryl(alkyl)coumarins. Whereas these reactions can also be performed with similar efficiency in THF by employing DBU, the IL approach offers easier work-up and recycling of the IL solvent. An IL-mediated approach to the synthesis of novel coumarin-bearing diaryl-ethynes by the Sonogshira reaction is also reported, and the potential for recycling/reuse of the IL solvent is shown.
- Kalkhambkar, Rajesh G.,Laali, Kenneth K.,Malunavar, Shruti S.,Prabhala, Pavankumar,Savanur, Hemantkumar M.,Sutar, Suraj M.
-
supporting information
(2020/04/08)
-
- Regioselective 3-O-Substitution of Unprotected Thiodigalactosides: Direct Route to Galectin Inhibitors
-
The synthesis of tailored bioactive carbohydrates usually comprises challenging (de)protection steps, which lowers synthetic yields and increases time demands. We present here a regioselective single-step introduction of benzylic substituents at 3-hydroxy groups of β-d-galactopyranosyl-(1→1)-thio-β-d-galactopyranoside (TDG) employing dibutyltin oxide in good yields. These glycomimetics act as inhibitors of galectins—human lectins, which are biomedically attractive targets for therapeutic inhibition in, for example, cancerogenesis. The affinity of the prepared glycomimetics to galectin-1 and galectin-3 was studied in enzyme-linked immunosorbent (ELISA)-type assays and their potential to inhibit galectin binding on the cell surface was shown. We used our original in vivo biotinylated galectin constructs for easy detection by flow cytometry. The results of the biological experiments were compared with data from molecular modeling with both galectins. The present work reveals a facile and elegant synthetic route for the preparation of TDG-derived glycomimetics that exhibit differing selectivity and affinity to galectins depending on the choice of 3-O-substitution.
- ?erveny, Jakub,Bojarová, Pavla,Bumba, Ladislav,K?en, Vladimír,Pelantová, Helena,Petrásková, Lucie,Spiwok, Vojtěch,Va?í?ek, Tomá?,Vrbata, David
-
supporting information
p. 9620 - 9631
(2020/08/05)
-
- Direct C-3 alkylation of coumarins via decarboxylative coupling with carboxylic acids
-
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.
- Jafarpour, Farnaz,Darvishmolla, Masoumeh,Azaddoost, Narges,Mohaghegh, Farid
-
supporting information
p. 9328 - 9332
(2019/06/21)
-
- Visible-light-induced regioselective alkylation of coumarins via decarboxylative coupling with N-hydroxyphthalimide esters
-
An efficient photocatalytic decarboxylative 3-position alkylation of coumarins by using alkyl N-hydroxyphthalimide esters as alkylation reagents has been developed. A variety of NHP esters derived from aliphatic carboxylic acids (primary, secondary, and tertiary) has been proved to be tolerated for this decarboxylation process, affording a broad scope of 3-alkylated coumarin derivatives in moderate to excellent yields. This protocol was highlighted by its mild conditions, readily available starting materials, operational simplicity, and wide functional group tolerance.
- Jin, Can,Yan, Zhiyang,Sun, Bin,Yang, Jin
-
supporting information
p. 2064 - 2068
(2019/04/11)
-
- Synthesis method of C-3 alkyl substituted coumarin derivative
-
The invention discloses a synthesis method of a C-3 alkyl substituted coumarin derivative. The synthesis method comprises the following steps: dissolving a coumarin derivative shown as a formula (I),an N-alkyloxyphthalimide compound shown as a formula (II), a photocatalyst and a proton acid in an organic solvent; reacting under visible light irradiation at a temperature of 20 to 60 DEG C for 3 to36 hours; after the reaction is finished, performing post-treatment on a reaction system to obtain a target product of the C-3 alkyl substituted coumarin derivative shown as a formula (III), whereinthe reaction formulas are shown in the description; in the formulas (I) and the formula (III), the substituent R1 is H, methyl, methoxy, fluorine, chlorine or bromine; in the formula (II) and the formula (III), the substituent R2 is linear alkyl or naphthenic alkyl of with 1 to 8 carbon atoms. The synthesis method realizes the C-3alkylation of coumarin with light as reaction energy, makes the reaction safer, more environmentally friendly and cheaper, expands the application range of the reaction substrate, and enriches the synthesis method of a C-3 substituted coumarin compound.
- -
-
Paragraph 0042-0044
(2019/06/12)
-
- Coumarin heterozygous pyridone compounds having iron chelation and monoamine oxidase B inhibitory activity as well as preparation and application of compounds
-
The invention discloses coumarin/pyridone heterozygous derivatives represented by a formula (I) shown in the description or a pharmaceutically-acceptable salt of the derivatives. The preparation method of the coumarin/pyridone heterozygous derivatives comprises the following steps: one pyridone derivative represented by a formula 3 shown in the description is obtained by a series of synthesis by using one hydroxypyrone with different substituent groups represented by a formula 1 shown in the description as a raw material; and a compound represented by a formula 4 shown in the description is subjected to a condensation reaction to obtain a compound represented by a formula 5 shown in the description, one-step bromination is performed to obtain a compound represented by a formula 6 shown inthe description, the compound represented by the formula 6 and the pyridone derivative represented by the formula 3 are subjected to a one-step nucleophilic substitution reaction to obtain a compoundrepresented by a formula 7 shown in the description, and finally an alkyl protecting group in a pyridone structure is removed to obtain one target compound represented by the formula (I). The compounds provided by the invention are a novel series of single-molecular multi-target series drugs, and have iron chelation, targeted MAO-B inhibitory activity, antioxidant activity, unique advantages for an Alzheimer disease with complicated pathogenesis, a clear mechanism of action and excellent activity.
- -
-
Paragraph 0057; 0061; 0161; 0166; 0265; 0270
(2019/10/01)
-
- Design, synthesis and biological evaluation of hydroxypyridinone-coumarin hybrids as multimodal monoamine oxidase B inhibitors and iron chelates against Alzheimer's disease
-
A series of hybrids of hydroxypyridinone and coumarin were rationally designed, synthesized and biologically evaluated for their iron ion chelating and MAO-B inhibitory activities. Most of the compounds displayed excellent iron ion chelating effects and moderate to good anti-MAO-B activities. Compound 27a exhibited the most potent activity against MAO-B, with an IC50 value of 14.7 nM. Importantly, 27a showed good U251 cell protective effect and significantly ameliorated the cognitive dysfunction of scopolamine-induced AD mice. Moreover, molecular docking was performed to elucidate the probable ligand-receptor interaction, and the structure-activity relationships were also summarized.
- Zhang, Changjun,Yang, Ke,Yu, Sihang,Su, Jing,Yuan, Shengli,Han, Jiaxin,Chen, Yan,Gu, Jinping,Zhou, Tao,Bai, Renren,Xie, Yuanyuan
-
p. 367 - 382
(2019/07/19)
-
- Design, synthesis, and mechanism of dihydroartemisinin-coumarin hybrids as potential anti-neuroinflammatory agents
-
Cancer patients frequently suffer from cancer-related fatigue (CRF), which is a complex syndrome associated with weakness and depressed mood. Neuroinflammation is one of the major inducers of CRF. The aim of this study is to find a potential agent not only on the treatment of cancer, but also for reducing CRF level of cancer patients. In this study, total-thirty new Dihydroartemisinin-Coumarin hybrids (DCH) were designed and synthesized. The in vitro cytotoxicity against cancer cell lines (HT-29, MDA-MB-231, HCT-116, and A549) was evaluated. Simultaneously, we also tested the anti-neuroinflammatory activity of DCH. DCH could inhibit the activated microglia N9 release of NO, TNF-α, and IL-6. The docking analysis was shown that MD-2, the coreceptor of TLR4, might be one of the targets of DCH.
- Yu, Haonan,Hou, Zhuang,Yang, Xiaoguang,Mou, Yanhua,Guo, Chun
-
-
- Synthesis of 7-Azido-3-Formylcoumarin – A Key Precursor in Bioorthogonally Applicable Fluorogenic Dye Synthesis
-
Coumarins represent an important group of natural products and a common part of various drugs and fluorescent dyestuffs. Herein, we present the synthesis of a coumarin that can serve as a key starting material in the design and synthesis of bioorthogonally applicable fluorogenic dyes. The synthesis of 7-azido-3-formylcoumarin started from 7-diallylaminocoumarin. This allyl protected aminocoumarin is otherwise hard to obtain by conventional methods but was conveniently accessed in good yields by a sequential, Wittig-reaction–UV isomerization process. This sequential approach was studied in more details and applied for the synthesis of a series of substituted coumarins even in one-pot.
- Pünk?sti, Zoltán,Kele, Péter,Herner, András
-
supporting information
p. 1183 - 1188
(2018/03/21)
-
- Visible-Light-Driven alkyne hydro-/carbocarboxylation using CO2 via iridium/cobalt dual catalysis for divergent heterocycle synthesis
-
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.
- Hou, Jing,Ee, Aloysius,Feng, Wei,Xu, Jin-Hui,Zhao, Yu,Wu, Jie
-
supporting information
p. 5257 - 5263
(2018/04/24)
-
- Pd/Al2O3-catalysed redox isomerisation of allyl alcohol: Application in aldol condensation and oxidative heterocyclization reactions
-
The application of the Pd/Al2O3 catalyst in allyl alcohol isomerization and subsequent aldol condensation and heterocyclization reactions is described. The activity of Pd/Al2O3 in these transformations is suggested to be due to the participation of the Lewis acidic sites of the support in the activation of the alcohol towards oxidative dehydrogenation by the metal and subsequent hydride transfer. The resulting enol(ate)/aldehyde could undergo further reactions promoted by the acid-base properties of the support. In the aldol condensation reactions of the isomerization product, electron poor aromatic aldehydes and heteroaromatic aldehydes showed the highest activity, while aromatic aldehydes bearing electron donating substituents reacted after transformation to the corresponding N-tosyl imines. 1,2-Disubstituted aromatics gave heterocyclic products in one-pot multistep reaction sequences.
- Zsolnai, Dániel,Mayer, Péter,Szori, Kornél,London, Gábor
-
p. 3814 - 3820
(2016/06/13)
-
- Regioselective Coupling Reactions of Coumarins with Aldehydes or Di-tert-butyl Peroxide (DTBP) through a C(sp2)-H Functionalization Process
-
Coumarin derivatives are highly valuable compounds in drug discovery. Herein, we have developed two new coupling reactions that involve coumarins and either aldehydes or di-tert-butyl peroxide (DTBP) in the presence of inexpensive copper or iron catalysts. Both of these reactions proceed through a C(sp2)-H functionalization process to regioselectivity generate keto- or methyl-substituted coumarin derivatives in moderate to good yields These coupling reactions will enrich current coumarin chemistry.
- Zhao, Wannian,Xu, Lei,Ding, Yingcai,Niu, Ben,Xie, Ping,Bian, Zhaogang,Zhang, Denghong,Zhou, Aihua
-
p. 325 - 330
(2016/02/14)
-
- Direct β-C(sp3)-H Functionalization of Aliphatic Amines to α,β-Unsaturated Imines, Aldehydes, and Chromenes
-
A metal-free method for direct β-C(sp3)-H functionalization of aliphatic amine was developed. The method is based on a reaction that yields enamine directly from the corresponding aliphatic amine, which otherwise requires the aid of metallic reagent and/or external oxidant. The reaction is operationally simple, general, and highly efficient in functionalizing both cyclic and acyclic amines. Structurally diverse unsaturated imines were obtained from N-heterocycles, while acyclic amines provided 2-alkyl cinnamaldehyde and benzopyran derivatives with excellent E/Z-selectivity.
- Mandal, Sumana,Mahato, Sujit,Jana, Chandan K.
-
supporting information
p. 3762 - 3765
(2015/08/18)
-
- Synthesis and biological evaluation of coumarin-1,2,3-triazole- dithiocarbamate hybrids as potent LSD1 inhibitors
-
Two series of coumarin-1,2,3-triazole-dithiocarbamate hybrids were designed, synthesized and evaluated for their inhibitory activity towards lysine specific demethylase 1 (LSD1). Compounds 8a, 8d-8f, 8i-8l presented potent activity against lysine specific demethylase 1. Among them, compound 8k showed potent and reversible inhibition against lysine specific demethylase 1 with an IC50 value of 0.39 μM, which was 74-fold more potent than that of tranylcypromine (2-PCPA). Besides, compound 8k displayed excellent selectivity against lysine specific demethylase 1 without inhibition against monoamine oxidases (MAOs) A and B. Further investigation revealed that compound 8k was active at both recombinant and cell levels by upregulating the expression of H3K4me1, H3K4me2 and H3K9me2. This journal is the Partner Organisations 2014.
- Ye, Xian-Wei,Zheng, Yi-Chao,Duan, Ying-Chao,Wang, Meng-Meng,Yu, Bin,Ren, Jing-Li,Ma, Jin-Lian,Zhang, En,Liu, Hong-Min
-
supporting information
p. 650 - 654
(2014/05/06)
-
- Convenient synthesis of 3-methylcoumarins and coumarin-3-carbaldehydes
-
Rapid, microwave-assisted Baylis-Hillman reactions of substituted salicylaldehydes, followed by one-pot hydrogen iodide-mediated cyclization and reduction of the corresponding adducts, has afforded 3-methylcoumarins in up to 94% yield in the final step. Subsequent microwave-assisted selenium dioxide oxidation of selected 3-methylcoumarins has provided convenient access to the corresponding coumarin-3-carbaldehydes and permitted a significant improvement over the yield obtained using conventional heating. Taylor & Francis Group, LLC.
- Olomola, Temitope O.,Klein, Rosalyn,Kaye, Perry T.
-
experimental part
p. 251 - 257
(2011/11/07)
-
- Catalytic synthesis of coumarins via direct annulations of α,β-unsaturated aldehydes and salicylaldehydes
-
The first organocatalytic approach towards substituted coumarins is reported. Catalytic amounts of in situ generated N-heterocyclic carbenes (NHC) catalyze a one-pot redox esterification of α,β-unsaturated aldehydes with simultaneous aldol condensation. Georg Thieme Verlag Stuttgart - New York.
- Gross, Ulrike,Gross, Patrick J.,Shi, Min,Br?se, Stefan
-
supporting information; experimental part
p. 635 - 638
(2011/04/26)
-
- Decarboxylative ketone aldol reactions: Development and mechanistic evaluation under metal-free conditions
-
(Chemical Equation Presented) Malonic acid half thioesters (MAHTs) and malonic acid half oxyesters (MAHOs) are shown to undergo decarboxylative nucleophilic addition reactions with ketone and aldehyde electrophiles in the presence of stoichiometric or catalytic quantities of triethylamine at room temperature. The ability to perform these reactions under metal-free conditions has enabled a detailed mechanistic analysis of the reaction pathway leading to the 1H NMR spectroscopic characterization of a postnucleophilic addition/predecarboxylation intermediate and experimental evidence for a reversible formation of this intermediate followed by an irreversible decarboxylation. Rate constants for each of the bond forming/bond breaking steps in the reaction pathway were also determined, casting light on the differing reactivity betweenMAHOandMAHT nucleophiles in these processes. Finally, the mechanistic insights gained through these studies have been employed in the development of a new decarboxylative coumarin synthesis.
- Blaquiere, Nicole,Shore, Daniel G.,Rousseaux, Sophie,Fagnou, Keith
-
supporting information; experimental part
p. 6190 - 6198
(2009/12/24)
-
- Synthesis of 3-alkylcoumarins from salicylaldehydes and α,β-unsaturated aldehydes utilizing nucleophilic carbenes: A new umpoled domino reaction
-
Starting from salicylaldehydes and α,β-unsaturated aldehydes, a new coumarin synthesis in ionic liquids is presented. The key feature is the generation of N-heterocyclic carbenes (NHC) and an Umpolung reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Toraeng, Jakob,Vanderheiden, Sylvia,Nieger, Martin,Braese, Stefan
-
p. 943 - 952
(2008/02/13)
-
- Synthesis of 3-substituted coumarins from 2-(acyloxy)arylaldehydes using the TiCl4/R3N reagent system
-
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.
- Suresh, Surisetti,Periasamy, Mariappan
-
p. 688 - 690
(2007/10/03)
-
- Synthesis of coumarins, 4-hydroxycoumarins, and 4-hydroxyquinolinones by tellurium-triggered cyclizations
-
Coumarins, 4-hydroxycoumarins, and 4-hydroxyquinolin-2(1H)-ones can be conveniently prepared by treatment of α-halocarboxylic acid esters of salicylaldehyde, o-hydroxyacetophenone, methyl salicylate, and methyl N-methyl- or N-phenylanthranilates with sodium or lithium telluride. Phenylketene formation competes with cyclization of the α-chlorophenylacetate ester of methyl salicylate as demonstrated by a trapping experiment with benzylamine. Elemental tellurium may be recovered and reused.
- Dittmer, Donald C.,Li, Qun,Avilov, Dimitry V.
-
p. 4682 - 4686
(2007/10/03)
-
- Application of Baylis-Hillman methodology in the synthesis of coumarin derivatives
-
A general, chemoselective approach to 3-substituted coumarins via Baylis-Hillman reactions of O-benzylated salicylaldehyde precursors has been demonstrated. Competitive cyclization to chromene derivatives is inhibited by conjugate addition of benzylamine or piperidine to the α,β-unsaturated ester intermediates.
- Kaye, Perry T.,Musa
-
p. 1755 - 1770
(2007/10/03)
-
- P(RNCH2CH2)3N: An efficient promoter for the synthesis of 3-substituted coumarins
-
The title compounds wherein R = Me or i-Pr function as efficient promoters for the formation of coumarins in good to excellent yields (80-95%) from salicylaldehydes and di-activated methylene compounds of the type R′CH2CO2Et (R′ = CO2Et, COMe, CN). Although the yields are not generally superior to those reported in the literature, our methodology is more convenient in that milder conditions and shorter reaction times are facilitated by the use of the aforementioned commercially available catalysts.
- Kisanga, Philip,Fei, Xiangshu,Verkade, John
-
p. 1135 - 1144
(2007/10/03)
-
- Rhodium-catalysed cyclic carbonylation of 2-alkynylphenols: Synthesis of benzofuranones and coumarins
-
Rhodium-catalysed carbonylation of 2-alkynylphenols 1 under water-gas shift reaction conditions gives benzofuranone derivatives 2 and coumarin derivatives 3 in high yield (up to 96%, 2:3 = 65:35), in which the hydroxy group adjacent to the carbon-carbon triple bond participitates in the cyclic carbonylation.
- Yoneda, Eiji,Sugioka, Takashi,Hirao, Kojiro,Zhahg, Shi-Wei,Takahashi, Shigetoshi
-
p. 477 - 483
(2007/10/03)
-
- Synthesis of Coumarins by Flash Vacuum Pyrolysis of 3-(2-Hydroxyaryl)propenoic Esters
-
Flash vacuum pyrolysis of 3-(2-hydroxyaryl)propenoic esters gives coumarins (and other fused α-pyrones) in high yieid.
- Cartwright, Gary A.,McNab, Hamish
-
p. 296 - 297
(2007/10/03)
-
- A Novel Acylative Cyclization Reaction of Phenol over Modified Y Zeolites
-
A novel acylative cyclization reaction of phenol and acetic anhydride to give 4-methylcoumarin (>70percent) over CeNaY zeolite is reported.
- Rao, Y. V. Subba,Kulkarni, S. J.,Subrahmanyam, M.,Rao, A. V. Rama
-
p. 1456 - 1457
(2007/10/02)
-
- Carboxylic Esters as Radical Leaving Groups: A New and Efficient Gas-phase Synthesis of Benzofurans
-
Flash vacuum pyrolysis (FVP) of o-allyloxycinnamate esters gives benzofurans in high yield, via cyclisation of a phenoxyl radical and subsequent cleavage of the carboxylic ester function; coumarins are obtained by FVP of the corresponding phenols.
- Black, Michael,Cadogan, J. I. G.,Cartwright, Gary A.,McNab, Hamish,MacPherson, Andrew D.
-
p. 959 - 960
(2007/10/02)
-
- CONJUGATE ADDITIONS ON α-PHENYLTHIO-α,β-UNSATURATED OXAZOLINES. NOVEL SYNTHESIS OF 3,4-DISUBSTITUTED COUMARINS.
-
Nucleophilic addition of organolithium, Grignard and hydride reagents to α-phenylthio-α,β-unsaturated oxazolines is regioselective and occurs in a 1,4-fashion.This leads to a novel, versatile synthesis of polysubstituted coumarins.
- Clinet, J. C.
-
p. 5901 - 5904
(2007/10/02)
-
- Synthesis of the Nitrile and Some Esters of 3,3-Dimethyl-2-oxochroman-4-acetic Acid
-
It is shown that the previously found rearrangement can be applied on the nitrile 4 (X=CN) when the anhydride used possesses only one α-hydrogen atom.Refluxing of this nitrile with isobutyric anhydride in the presence of triethylamine leads to the expected rearrangement product 5 (X=CN).Making use of the same anhydride, the esters 4 (X=COOR) are converted into esters 5 (X=COOR).
- Bojilova, A.,Ivanov, Chr.
-
p. 415 - 416
(2007/10/02)
-
- STUDIES IN CLAISEN REARRANGEMENT; NOVEL THERMAL TRANSFORMATION OF α-ARYLOXYMETHYLACRYLIC ACIDS AND THEIR DERIVATIVES
-
α-Aryloxymethylacrylic acids and their derivatives have been found to undergo some novel thermal transformations leading to the formation of 'ene' dimers.The structure of the dimer has been revised on the basis of degradation studies, extensive spectral data and isolation of intermediates.
- Gopalan, B.,Rajagopalan, K.,Sunitha, K.,Balasubramanian, K. K.
-
p. 3153 - 3160
(2007/10/02)
-
- A ONE STEP GENERAL SYNTHESIS OF 3-SUBSTITUTED COUMARINS
-
A one step, general synthesis of 3-phenyl and 3-alkyl coumarins, using substituted acetamides and o-hydroxy benzaldehydes is reported.
- Phadke, Chetan P.,Kelkar, Shriniwas L.,Wadia, Murzban S.
-
p. 407 - 412
(2007/10/02)
-
- An Improved Synthesis of 3-Methylcoumarins and Their Linear and Angular Benzo Derivatives
-
Hydroxybenzaldehydes (1a-k) on reaction with triphenyl-α-ethoxycarbonylpropylidenephosphorane (2) furnish 3-methylcoumarins (3a-k) in excellent yields.
- Mali, R. S.,Yeola, Suresh N.,Kulkarni, B. K.
-
p. 352 - 354
(2007/10/02)
-