Microwave-assisted synthesis of coumarin-3-carboxylic acids under ytterbium triflate catalysis

Fiorito, Serena; Genovese, Salvatore; Taddeo, Vito Alessandro; Epifano, Francesco

doi:10.1016/j.tetlet.2015.03.079

Cited by 38 publications

(20 citation statements)

References 18 publications

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“…48 Hence, chemists have been greatly motivated to explore useful synthetic strategies for such novel and promising targets for subsequent research and development. 49 3 Among various available methods, Knoevenagel condensation is widely used for the synthesis of coumarin-3-carboxylic acids from the reaction between ortho-hydroxyaryl aldehydes with differently substituted malonates or cyanoacetates in the presence of a number of catalysts such as piperidine, 50,51 piperidinium acetate, 52 and ammonium acetate. 53,54 An exhaustive review on the synthesis of coumarin derivatives via Knoevenagel condensation has recently been recently reported.…”

Section: Introductionmentioning

confidence: 99%

“…55 However, use of Meldrum's acid as the β-dicarbonyl compound in the targeted Knoevenagel condensation has become the choice today because of several advantages in terms of yields, reaction times and purification of adducts. There are many reports so far on the condensation of ortho-hydroxyaryl carbonyls and Meldrum's acid involving the use of a variety of catalysts like ammonium acetate, 56 triethyl benzyl ammonium chloride and potassium phosphate, 57 SnCl 2 , 58 FeCl 3 , 30 clays, 59 lithium salts, 60 silica sulphuric acid, 61 and Yb(OTf) 3 /MW 49 . Although these protocols reported by others find certain merits of their own, still they suffer from a number of demerits such as harsh reaction conditions, low yields, tedious work-up procedures, co-occurrence of several side reactions, use of toxic organic solvents and need of chromatography for purification of adducts.…”

Section: Introductionmentioning

confidence: 99%

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Room Temperature One-Pot Green Synthesis of Coumarin-3-carboxylic Acids in Water: A Practical Method for the Large-Scale Synthesis

Brahmachari

2015

ACS Sustainable Chem. Eng.

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A simple, facile and convenient practical method for the room temperature one-pot synthesis of a series of potentially biologically active coumarin-3-carboxylic acids has been developed in water from the Knoevenagel condensation and intramolecular cyclization of diverse 2hydroxybenzaldehydes with Meldrum's acid using either potassium carbonate or sodium azide as commercially available, cheap and eco-friendly catalyst. The salient features of the present protocol are mild reaction conditions, good to excellent yields, high atom-economy, environmentally benignity, easy isolation of products, without column chromatography, clean reaction profiles and applicability towards large-scale synthesis.General. Infrared spectra were recorded using a Shimadzu (FT-IR 8400S) FT-IR spectrophotometer using KBr disc. 1 H and 13 C NMR spectra were obtained at 400 MHz and 100 MHz respectively, using Bruker DRX-400 spectrometer and DMSO-d 6 as the solvent.Mass spectra (TOF-MS) were measured on a QTOF Micro mass spectrometer. Elemental analyses were performed with an Elementar Vario EL III Carlo Erba 1108 micro-analyzer instrument. X-ray data were collected on a Bruker single crystal X-ray difractometer (model:APEX 2). Melting point was recorded on a Chemiline CL-726 melting point apparatus and is uncorrected. Thin Layer Chromatography (TLC) was performed using silica gel 60 F 254 (Merck) plates. General procedure for the synthesis of coumarin-3-carboxylic acids (3): An oven-driedscrew cap test tube was first charged with a magnetic stir bar, salicylaldehydes (1, 1.0 mmol), Meldrum's acid (2, 1.0 mmol; 144 mg), distilled water (5 mL) and K 2 CO 3 (20 mol%; 28 mg).The whole mixture was then stirred vigorously at room temperature (24-26 ο C) for 20 h to complete the conversion. Upon completion, the resulting solution was acidified with chilled acid-water, when solid mass precipitated out, filtered off and thoroughly washed with water to obtain almost pure product of coumarin-3-carboxylic acids 3. For further purification, the products were crystallized from ethyl acetate. All the products 3 were also synthesized repeating the same reaction using sodium azide (50 mol%; 33 mg) as the catalyst in place of potassium carbonate. The structure of each purified product was confirmed by its analytical as well as spectral studies including FT-IR, 1 H NMR, 13 C NMR and TOF-MS. For few entries, 2D-NMR ( 1 H-1 H COSY, HMQC and HMBC) spectral properties were also studied.In addition, single X-ray crystallographic studies for one entry, 6-methoxycoumarin-3carboxylic acid (3f), was performed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Room Temperature One-Pot Green Synthesis of Coumarin-3-carboxylic Acids in Water: A Practical Method for the Large-Scale Synthesis

Brahmachari

2015

ACS Sustainable Chem. Eng.

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“…When the temperature was increased from room temperature to 50 ∘ C, the yield of product increased. In recent years, the field of greener catalysts such as reusable lanthanide triflates, organocatalysts, biodegradable reagents, and ionic liquids has an increasing importance in synthetic organic chemistry [67][68][69][70]. In order to observe the effect of several greener catalysts and ionic liquids such as Bi(OTf) 3 , Sc(OTf) 3 , Yb(OTf) 3 , VB1 (thiamine hydrochloride), (+)-CSA (camphor-10-sulfonic acid), 1-benzyl-3-methylimidazoliumchloride (IL1), 1-ethyl-2,3-dimethylimidazoliumtetrafluoroborate (IL2), and 8-ethyl-1,8-diazabicyclo [5,4,0]-7-undecenium trifluoromethanesulfonate (IL3), they were examined under ultrasound irradiation (Table 1) at 50 ∘ C. As a result, (+)-CSA was found to be the most effective catalyst at 50 ∘ C for this reaction.…”

Section: Resultsmentioning

confidence: 99%

(+)-CSA Catalyzed Multicomponent Synthesis of 1-[(1,3-Thiazol-2-ylamino)methyl]-2-naphthols and Their Ring-Closure Reaction under Ultrasonic Irradiation

Pelit

Turgut

2016

Journal of Chemistry

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New 1-[(1,3-thiazol-2-ylamino)methyl]-2-naphthols were obtained by condensation of 2-aminothiazole, aromatic aldehydes, and 2-naphthol in the presence of (+)-camphor-10-sulfonic acid ((+)-CSA) as an effective catalyst under ultrasound-promoted solvent-free conditions. The 1-[(1,3-thiazol-2-ylamino)methyl]-2-naphthol derivatives were converted in ring-closure reaction with formaldehyde to the corresponding naphthoxazine derivatives.

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“…Apart from these applications, coumarin‐3‐carboxylic acids have been widely used as fluorescent probes[96a] and triplet oxygen sensitizers [96b]. Hence, chemists have been greatly motivated to explore useful synthetic strategies for such novel and promising targets for subsequent research and development …”

Section: Designing Organic Transformations At Ambient Conditionsmentioning

confidence: 99%

Design of Organic Transformations at Ambient Conditions: Our Sincere Efforts to the Cause of Green Chemistry Practice

Brahmachari

2015

The Chemical Record

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This account summarizes our recent efforts in designing a good number of important organic transformations leading to the synthesis of biologically relevant compounds at room temperature and pressure. Currently, the concept of green chemistry is globally acclaimed and has already advanced quite significantly to emerge as a distinct branch of chemical sciences. Among the principles of green chemistry, one principle is dedicated to the "design of energy efficiency" - that is, to develop synthetic strategies that require less or the minimum amount of energy to carry out a specific reaction with optimum productivity - and the most effective way to save energy is to develop strategies/protocols that are capable enough to carry out the transformations at ambient temperature! As part of on-going developments in green synthetic strategies, the design of reactions under ambient conditions coupled with other green aspects is, thus, an area of current interest. The concept of developing reaction strategies at room temperature and pressure is now an emerging field of research in organic chemistry and is progressing steadily. This account is aimed to offer an overview of our recent research works directly related to this particular field of interest, and highlights the green chemistry practice leading to carbon-carbon and carbon-heteroatom bond-forming reactions of topical significance. Green synthetic routes to a variety of biologically relevant organic molecules (heterocyclic, heteroaromatic, alicyclic, acyclic, etc.) at room temperature and pressure are discussed.

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Microwave-assisted synthesis of coumarin-3-carboxylic acids under ytterbium triflate catalysis

Cited by 38 publications

References 18 publications

Room Temperature One-Pot Green Synthesis of Coumarin-3-carboxylic Acids in Water: A Practical Method for the Large-Scale Synthesis

Room Temperature One-Pot Green Synthesis of Coumarin-3-carboxylic Acids in Water: A Practical Method for the Large-Scale Synthesis

(+)-CSA Catalyzed Multicomponent Synthesis of 1-[(1,3-Thiazol-2-ylamino)methyl]-2-naphthols and Their Ring-Closure Reaction under Ultrasonic Irradiation

Design of Organic Transformations at Ambient Conditions: Our Sincere Efforts to the Cause of Green Chemistry Practice

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