Melamine–formaldehyde resin supported H+ a mild and inexpensive reagent for synthesis of coumarins under mild conditions (original) (raw)
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Comptes Rendus Chimie, 2012
Coumarins are used in the fields of biology, medicine, and polymer science. They are also present or used in perfumes and cosmetics [1-3], alcoholic beverages [4], and laser dyes [5-9]. In addition to these uses, coumarins are well documented as therapeutic agents and have been used as medicines in ancient Egypt and in aboriginal cultures [10,11]. One example, warfarin, is the most prescribed anti-coagulant on the market [12,13]. Recently, coumarin derivatives were utilized to synthesize of photoreversible polymer systems [14-16]. Coumarin derivatives were first synthesized via the Perkin reaction in 1868, and many simple coumarins are still derived from this method. In the early 1900s, the Knoevenagel reaction emerged as an important synthetic method to synthesize coumarin derivates with carboxylic acids at the three positions [17,18]. Later, researchers condensed etylcyanoacetate and various o-hydroxyacetophenones to synthesize 4-methylcoumarine derivatives [19,20]. In the conventional production of coumarins by the Pechmann reaction, concentrated sulfuric acid is used as the catalyst [21]. However, as an alternative to sulfuric acid, other acid catalysts such as Montmorillonite clay [22], [bmim]Cl.2AlCl 3 [23], InCl 3 [24], P 2 O 5 /molecular sieve 3A8 [25], sulfamic acid [26], BiCl 3 [27], VCl 3 [28], zeolite [29], ZrOCl 2 .8H 2 O [30], HClO 4 .SiO 2 [31], sulfated zirconia [32], Keggin heteropoly acids [33], SnCl 2 .2H 2 O [34] and sulfonic acid nanoreactors [35] are employed to improve the Pechmann reaction. However, some of these methods suffer from at least one of the following disadvantages: moisture sensitivity of the majority of Lewis acids to the water produced in the Pechmann condensation renders them unsuitable for use in large scale application, strongly acidic wastes, high cost and toxicity of the reagent, tedious work-up procedures, unsatisfactory yields, and nonrecyclable reagents. Therefore, it seems that the major task of current research is to replace both homogeneous and less efficient and traditional
2017
Coumarins have been synthesized by microwave irradiation in solvent free reaction condition, and excellent yields of coumarins have been obtained with high purity. Pechmann method is a revere reaction which is one of the easy and forthright scheme used to produce coumarins. IR and NMR spectroscopy have been used to confirm the successful synthesis of coumarins by Pechmann reaction. Use of commercially accessible low-cost catalyst makes this procedure very fascinating from a cost-effective point of view. An easygoing and capable microwave synthesis technique has been evolved for condensation of β-ketoester and substituted phenol in the presence of catalytic quantity of oxalic acid at extensive temperature range to give the resultant substituted 4-methyl-2 H -chromen-2-one in elevated output.
Solvent-free coumarin synthesis via Pechmann reaction using solid catalysts
Microporous and Mesoporous Materials, 2012
A solvent-free versatile and efficient methodology, reported here, allows the synthesis of coumarin by hydroxyalkylation of phenols with ethyl or methyl acetoacetate (via Pechmann reaction) using trifluoromethanesulfonic acid (triflic acid) functionalised Zr-TMS (Zr-TMS, zirconia based transition metal oxide mesoporous molecular sieves) catalysts with different loadings of triflic acid over Zr-TMS (5-25 wt.%) where the total acid strength of acid functionalised Zr-TMS material is increased as increasing loading of triflic acid from 5 to 25 wt.% leading to correspond increased higher catalytic activity.
Indian Journal of Chemical Technology
Pechmann reaction is mainly used for the synthesis of substituted coumarins as it can be executed with straight forward primary resources and gives coumarin derivatives with excellent yields. In the present work coumarin derivatives have been synthesized by condensation of β-ketoesters and substituted phenols under microwave irradiation in solvent free condition in which oxalic acid is used as catalyst. Oxalic acid is found to be a potential environment friendly catalyst for synthesis of coumarins. The new method of synthesis described here offers a number of advantages of being convenient, safe, gentle, shorter reaction time, high yield, and cleanness as compared to the conventional methods. The synthesized compounds have been systematically characterized by IR and MS analyses. All products are examined for antimicrobial activity against the Gram positive (Staphylococcus aureus and Bacillus subtilis) and Gram negative (Escherichia coli and Salmonella typhi) bacteria and antifungal activity against two fungal species (Aspergillus sp. and Fusarium graminearum). All the compounds inhibited the growth of bacteria as well as fungi.
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.