Melamine–formaldehyde resin supported H+ a mild and inexpensive reagent for synthesis of coumarins under mild conditions (original) (raw)
ACS Omega
A novel heterogeneous catalytic method was developed for the synthesis of coumarin and its derivatives using the Ti(IV)doped ZnO matrix forming catalyst Zn 0.925 Ti 0.075 O having a high surface area and good Lewis acidity. The catalyst shows high activity toward a broad spectrum of the substituted phenols with β-ketoesters such as ethyl acetoacetate, ethyl butyryl acetate, ethyl benzoyl acetate, and so forth in good yields over short reaction times during the synthesis of coumarins. The methodology was further extended for the synthesis of ayapin molecules. The catalyst also shows recycle activity up to seven cycles with very good stability. ■ INTRODUCTION Coumarins are a class of oxygen heterocycles, contributing in the field of natural products which are medicinally important. 1 Coumarin derivatives are utilized as intermediate chemicals in the synthesis of pharmaceuticals, agrochemicals, insecticides, food additives, fragrances, and cosmetics. 2 Additionally, they are applicable as optical whitening agents, laser colors, dyes, and fluorescent probes for the identification of biologically important chemical species as medicinal stains. 3 In the synthetic organic chemistry, the class of coumarin compounds is useful for the synthesis of chromones, coumarones, fluorocoumarins, and 2-acyl resorcinol. 4 However, many important drug molecules have coumarin moieties such as warfarin, calanolide A, 667 coumate, novobiocin, ensaculin alexa 350, hymecromone, and umbelliferone (Figure 1). In the past reports, novel and well-organized methodologies have been developed to prepare coumarin compounds. Currently, the number of methods are available for the coumarin synthesis such as Pechmann reaction, 5 Knoevenagel condensation, 6 Claisen rearrangement, 7 Perkin, 8 Wittig, 9 Reformatsky, 10 catalytic cyclization, 11 flash vacuum pyrolysis, 12 and so forth. Amongst all, Pechmann reaction is widely useful for the synthesis of coumarin because of the simple starting materials, mild reaction conditions, and excellent yields of the products in short reaction times.
Journal of The Chinese Chemical Society, 2019
A convenient, practical, green, and environmentally friendly method was developed for the synthesis of biscoumarins and corresponding tetrakis products from the reaction of 4-hydroxycoumarin and various aldehydes. The bis-coumarins were synthesized in high yield under mild reaction conditions. Products were obtained in the presence of in situ prepared Fe(SD) 3 [Iron(III) dodecyl sulfate] as a combined Lewis acid-surfactant catalyst (LASC) in water in short reaction times. Also, the antibacterial activity of compounds was screened against Pseudomonas aeruginosa and Escherichia coli as Gram-negative bacteria and Micrococcus luteus and Staphylococcus aureus as Gram-positive bacterial strains. Products 3g, 3k-l were most active than cefotaxime against E. coli and also compounds 3c and 3g were most active than cefotaxime against S. aureus. K E Y W O R D S 4-Hydroxycoumarin, bis-coumarins, green synthesis, terephthaldehyde, tetrakis-coumarins 1 | INTRODUCTION Coumarin derivatives are an important class of heterocyclic compounds and their biological activities make them interesting targets for multicomponent reactions (MCRs). Moreover, their biological activities involve HIV inhibitory, [1] antibacterial, [2] anticancer, [3] anticoagulant, [4] antihepatitis C virus, [5] vasorelaxants, [6] enzymatic inhibitors, [7] antitumor, [8] and spasmolytic [9] activities. Also, coumarins are used as food and cosmetic additives and as brightening agents. [10,11] Synthetic routes to coumarins include Pechmann condensation, Perkin, Knoevenagel, and Reformatsky reactions as well as flash vacuum pyrolysis. [12] Among these, the Knoevenagel reaction is the most commonly applied one, in which different types of acid catalysts such as H 2 SO 4 , P 2 O 5 , AlCl 3 , I 2 , and F 3 CCO 2 H are employed. [13,14] Many of the reactions are undesirable for industrial purposes due to difficult conditions, longer reaction times and corrosive reagents. Therefore, finding mild and economical synthetic methods is necessary to overcome the previous procedures. In 2009, Sangshetti et al. reported the use of MnCl 2 .4H 2 O for condensation of 4-hydroxycoumarin and aldehydes in H 2 O at 100 C in moderate to good yields (99%). [15] Other procedures that used microwaves [16] and ultrasound irradiation [17] have been carried out using catalysts such as molecular I 2 , [18] [bmim] [BF4], [19] (Bu) 4 NBr (TBAB), [20] sodium dodecyl sulfate (NaOSO 2 OC 12 H 25) (SDS), [21] P 4 VPy-CuO-NPs, [22] RuCl 3. nH 2 O, [23] sulfated titania [TiO 2 /SO 4 2− ], [24] Melamine trisulfonic acid (MTSA), [25] tetrabutylammonium hexatungstate [TBA] 2 [W 6 O 19 ], [26] Ni-NPs, [27] POCl 3 in dry dimethylformamide (DMF), [28] TiO 2 @KSF, [29] ZnO nanocomposite, [30] diethyl aluminum chloride (Et 2 AlCl), [31] LiClO 4 , [32] Piperidine, [33] nano-Fe 3 O 4 , [34] kit-6-mesoporous silica-coated magnetic nanoparticles, [35] amino glucosefunctionalized silica-coated NiFe 2 O 4 nanoparticles, [36] Fe 3 O 4 @SiO 2 @KIT-6, [37] [BDBDMIm]Br-CAN, [38] citric acid, [39] and SBPDSA. [40] More catalysts and different
A Solvent-Free Synthesis of Coumarins Using a Wells?Dawson Heteropolyacid as Catalyst
ChemInform, 2005
Substituted coumarins are synthesized from phenols and b-ketoesters by the Pechmann reaction, using a Wells-Dawson heteropolyacid (H 6 P 2 W 18 O 62 AE24H 2 O) as catalyst by a solvent-free procedure. This one requires low reaction times, 130°C temperature and as little as 1 mol % of Wells-Dawson acid, obtaining good to excellent yields of coumarins. The catalyst showed to be reusable with no differences in the yields. The results are compared with those of the reactions performed in toluene solution. The presented synthetic procedure is a convenient, clean and fast alternative for synthesizing 4-substituted coumarins (17 examples).
2016
An efficient route for the synthesis of 3-substituted coumarins via Knoevenagel condensation using ZrOCl 2 .8H 2 O (10 mol %) as the catalyst under microwave heating and solvent-free conditions is described. This procedure offers several advantages including low loading of catalyst, high yields, clean reaction, short reaction time and use of various substrates, which make it a useful and attractive strategy for the synthesis of 3-substituted coumarins.
Molecules (Basel, Switzerland), 2017
A suitable methodology of synthesis of coumarin derivatives by Pechmann reaction over heterogeneous solid acid catalysts in a free solvent media under microwave irradiation is described. Resorcinol, phenol and ethyl acetoacetate were selected as model reactants in the Pechmann condensation. The catalytic activity of several materials-Amberlyst-15, zeolite β and sulfonic acid functionalized hybrid silica-in solvent-free microwave-assisted synthesis of the corresponding coumarin derivatives has been investigated in detail. 7-Hydroxy-4-methylcoumarin and 4-methylcoumarin were obtained in 97% and 43% yields, respectively, over Amberlyst-15. This was the most active catalyst in the Pechmann reaction under studied conditions.
Journal of Chemical Research-s, 2008
Dipyridine cobalt chloride is a novel catalyst for the Pechmann condensation involving different phenols and ethylacetoacetate under solvent-free conditions using both conventional methods and microwave irradiation. It gives the corresponding coumarins in excellent yields with high purity. The catalyst is thermally stable, inexpensive and recyclable. A faster reaction and higher yields compared to the conventional method and no side products were identified using microwave irradiation. In this reaction, electron releasing groups on the phenol ring shown more reactivity and gave high yields than simple phenol. These products were identified by 1 H NMR, 13 C NMR, MS, IR and elemental analysis.
Pechmann Reaction in the Synthesis of Coumarin Derivatives
Elsevier, 2014
The Pechmann reaction introduces one of the most significant and simple methods for the synthesis of a variety of heterocyclic compounds, particularly coumarin derivatives. In 1883, a German chemist, Hans von Pechmann synthesized coumarins from the reaction of phenols with a carboxylic acid or ester containing a β-carbonyl group. In this article, we try to highlight the various aspects, issues, and applications of this reaction.
Comptes Rendus Chimie, 2013
An environmentally benign Pechman protocol for the one-pot synthesis of 4-substituted coumarins through the condensation reactions of phenol substrates with b-ketoesters using polystyrene-supported GaCl 3 (PS-GaCl 3) as a highly active and reusable solid Lewis acid catalyst under mild and heterogeneous conditions in good to excellent yields is described. This new protocol is easy, simple, cost-effective, chemoselective, and in addition has the advantages of easy availability, stability, reusability and eco-friendly character of the catalyst, high to excellent yields, simple experimental and work-up procedure.
Catalysts, 2018
New modified acidic catalysts were prepared from the treatment of silica, titania and silica prepared from hydrolyzed tetraethyl orthosilicate (TEOS) with sulfuric and phosphoric acid. The sulfated and phosphated silica synthesized from TEOS were calcined at 450 and 650 • C. These catalysts were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), and scanning electron microscope (SEM). The surface areas, total pore volume, and mean pore radius of the acidic catalysts were investigated, while the pore size distribution was determined by the Barrett, Joyner and Halenda (BJH) method. The catalytic activity of the sulfated and phosphated silica and/or titania were examined with the Pechmann condensation reaction, in which different phenols reacted with ethyl acetoacetate as a neat reaction to obtain the corresponding coumarin derivatives. The results indicated that the treatment of the catalysts with sulfuric or phosphoric acid led to a decrease in the phases' crystallinity to a certain degree. The morphology and the structure of the acidified catalysts were examined and their particle size was calculated. Furthermore, the amount of the used catalysts played a vital role in controlling the formation of the products as well as their performance was manipulated by the number and nature of the active acidic sites on their surfaces. The obtained results suggested that the highest catalytic conversion of the reaction was attained at 20 wt % of the catalyst and no further increase in the product yield was detected when the amount of catalyst exceeded this value. Meanwhile the phenol molecules were a key feature in obtaining the final product.