The synthesis of coumarin-3-carboxylic acids and 3-acetyl-coumarin derivatives using heteropolyacids as heterogeneous and recyclable catalysts

a a d a Fa ces Az d fo ine well-defined structure, Bro¨nsted acidity, possibility to mod- ify their acid–base and redox properties by changing their of HPAs including, H14[NaP5W30O110], H4[PMo11VO40], H5[PMo10V2O40] and H6[P3W18O62] (Scheme 1). The less reactive 1-(2-hydroxy-phenyl)-ethanone was first reacted with alcoholic ammonia to form ketimines, which were then condensed with 1-ethylacetoacetate or malonic acid to generate 4-methyl coumarin-3-carboxylic * Corresponding author. Tel.: +98 2188041344; fax: +98 2188047861. E-mail addresses: [email protected] (M.M. Heravi), fbamohar- [email protected] (F.F. Bamoharram). Available online at www.sciencedirect.com Catalysis Communications 9 1. Introduction The synthesis of coumarins and their derivatives has attracted considerable attention from organic and medici- nal chemists for many years as a large number of natural products contain this heterocyclic nucleus. They are widely used as additives in food, perfumes, cosmetics [1], pharma- ceuticals and optical brighteners [2] and dispersed fluores- cent and laser dyes [3]. Thus the synthesis of this heterocyclic nucleus is of much interest. The application of heteropolyacids, HPAs, as catalytic materials is growing continuously in the catalytic field. These compounds possess unique properties such as: chemical composition (substituted HPAs), ability to accept and release electrons, high proton mobility, being environ- mentally benign and presenting fewer disposal problems [4]. Because of their stronger acidity, they generally exhibit higher catalytic activity than conventional catalysts such as mineral acids, ion exchange resins, mixed oxides, zeolites, etc. [5]. They are used as industrial catalysts for several liquid phase reactions [6], such as alcohol dehydration [7], alkylation [8] and esterification [9]. Herein we report the synthesis of coumarin-3-carboxylic acids and 3-acetyl-coumarins by cyclization of 2-hydroxyl- benzaldehyde derivatives and 1-ethylacetoacetate or malo- nic acid in the presence of a catalytic amount of different type Abstract Coumarin-3-carboxylic acids and 3-acetyl-coumarins were obtained in high yields with excellent purity from ortho-hydroxybenzaldehydes and 1-ethylacetoacetate or malonic acid after a 2 h reflux in ethanol in the presence of a catalytic amount of different heteropolyacids (HPAs). The less reactive 1-(2-hydroxy-phenyl)-ethanone was first reacted with alcoholic ammonia to form ketimines, which were then condensed with 1-ethylacetoacetate or malonic acid to generate 4-methyl coumarin-3-carboxylic acids and 4-methyl 3-acetyl-coumarins in moderate yields. � 2007 Elsevier B.V. All rights reserved. Keywords: Coumarin-3-carboxylic acids; 3-Acetyl-coumarins; Recyclable catalysts; Heteropolyacids The synthesis of coum and 3-acetyl-coumarin deriv as heterogeneous an Majid M. Heravi a,*, Samaheh S Rahim Hekmat Shoar a, a Department of Chemistry, School of Scien b Department of Chemistry, School of Sciences, Received 5 May 2007; received in revise Available onl 1566-7367/$ - see front matter � 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.catcom.2007.07.005 rin-3-carboxylic acids tives using heteropolyacids recyclable catalysts djadi a, Hossein A. Oskooie a, temeh F. Bamoharram b , Azzahra University, Vanak, Tehran, Iran ad University, Khorasan Branch, Mashad, Iran rm 19 June 2007; accepted 2 July 2007 10 July 2007 www.elsevier.com/locate/catcom (2008) 470–474 O OH R1 R2 R3 R5 O OR O O O O R5 R1 R2 R3 + Heteropolyacid solvent, reflux4 me M.M. Heravi et al. / Catalysis Communications 9 (2008) 470–474 471 acids and 4-methyl 3-acetyl-coumarins in moderate yields (Scheme 2). 2. Experimental 2.1. Chemicals and apparatus All the chemicals were obtained from Merck Company and used as received. H14[NaP5W30O110] was prepared according to earlier works [10]. H4[PMo11VO40] and H5[PMo10V2O40] were prepared according to the literatures [11]. The Wells–Dawson H6[P2W18O62] was prepared as described elsewhere [12] from an aqueous solution of a/b K6P2W18O62 Æ 10H2O salt, which was treated with ether and concentrated (37%) HCl solution. 2.2. General procedure 2.2.1. Synthesis of coumarin-3-carboxylic acids and 3-acetyl- coumarins A mixture of 2-hydroxyl-benzaldehyde derivatives (10 mmol) and 1-ethylacetoacetate or malonic acid (10 mmol) and heteropolyacid (1 mmol) in an appropriate solvent (10 mL) was refluxed for 2 h. The progress of the reaction was monitored by TLC using EtOAc: hexane (1:2) as eluents. Because of insolubility of these catalysts in ethanol [13–15], after completion of the reaction, the cat- alyst was filtered and the solvent was evaporated. The pure products were obtained by column chromatography. All products were identified by comparison of their physical and spectroscopic data with those reported for authentic samples. 2.2.2. Synthesis of 4-methyl coumarin-3-carboxylic acids and 4-methyl 3-acetyl-coumarins 1-(2-Hydroxy-phenyl)-ethanone (20 mmol) was mixed with 7 M ammonia solution in methanol (15 mL) overnight Sche at room temperature. Some crystals were formed the next day. The solvent and excess ammonia were removed. O OH R1 R2 R3 NH OH R1 R2 R3 NH3 Scheme Residue was refluxed with 1-ethylacetoacetate or malonic acid (20 mmol) and catalytic amount of heteropolyacids (2 mmol) in ethanol for 2 h, and then allowed to cool to room temperature. After complete precipitation, the prod- uct was filtered and recrystallized from aqueous acetone. The solvent was removed after the reaction. The residue was proportioned between 5% aqueous sodium carbonate solution (20 mL) and ethyl acetate (10 mL). The aqueous phase was acidified with 1 M HCl to pH 2, followed by extraction with ethyl acetate (10 mL · 3). The organic phase was combined, washed with water, dried over anhy- drous Na2SO4. The residue was recrystallized from aque- ous acetone. 2.3. Reusability of catalyst At the end of the reaction, the catalyst could be recov- ered by a simple filtration. The recycled catalyst could be washed with dichloromethane and subjected to a second run of the reaction process. To assure that catalysts were not dissolved in ethanol, the catalysts were weighted after filteration and before using and reusing for the next reac- tion. The results show that these catalysts are not soluble in ethanol. In Table 1, the comparison of efficiency of H14[NaP5W30O110] in synthesis of coumarin derivatives after five times is reported. As it is shown in Table 1 the yields of reactions after using H14[NaP5W30O110] for five times showed only slight decrease. 3. Results and discussion Due to the ever-mounting environmental concern in the field of chemistry, it is advisable to use easily recovered and recycled catalyst especially expensive or toxic metallic ones for the next use [16]. In this respect, only few of the afore- mentioned, catalysts meet this criterion of green chemistry. In connection with our program of using heteropoly 1. acid in organic reactions [15] we wish to report the result of a study on the use of three type of HPAs including R5 O OR O O O O R5 R1 R2 R3Heteropolyacid 4 ETOH, 2. of them, we cannot control the reaction conditions to synthesis of positional vanadium-substituted isomers sepa- rately, revealing the relationship between the structures of H3+xPMo12�xVxO40 (x = 1,2) and hence study of their cat- alytic activity, is difficult. However, because the metal sub- stitution may modify the energy and composition of the LUMO and redox properties, for mentioned heteropolyac- ids with different charges, the energy and composition of the LUMOs have significant effects on the catalytic activ- ity. Substitution of vanadium ions into the molybdenum framework stabilize the LUMOs because these orbitals derive, in part from vanadium d-orbitals which have been assumed to be more stable than those of molybdenum Table 1 The comparison of efficiency of H14[NaP5W30O110] in synthesis of coumarin derivatives after five times Entry R1 R2 R3 R4 R5 Yield% a (after different times of recycling) First Second Third Forth Fifth 1 H H H CH2CH3 CH3 98.2 97.5 96 95.5 93.2 2 H H H H OH 97 96.3 94.9 93.5 90.8 3 H OCH3 H CH2CH3 CH3 97 95.6 94.2 92.7 91.2 4 H H NO2 H OH 95.7 94.2 92.5 91.2 89.3 5 CH3 H H H OH 59 58.2 57.5 55.8 53.4 6 CH3 H H CH2CH3 CH3 65 63.6 62.2 60.6 59.3 a 11 CH3 H H H5[PMo10V2O40] 55 12 CH3 H H H4[PMo11VO40] 50 a Yields were analyzed by GC. 472 M.M. Heravi et al. / Catalysis Communications 9 (2008) 470–474 Preyssler, H14[NaP5W30O110], Keggin, H5[PMo10V2O40], H4[PMo11VO40] and Wells–Dawson, H6[P2W18O62] in the synthesis of coumarin derivatives and the effects of reaction parameters such as the type of HPA, temperature and reac- tion times on the yield of reaction. The results for H14[NaP5W30O110] are summarized in Table 2. The effects of different catalysts on synthesis of 3-acetyl-coumarins and coumarin-3-carboxylic acids are shown in Tables 3 and 4, respectively. 3.1. The structural characteristics of the catalysts are as follow Preyssler’s anion, [NaP5W30O110] 14�, has an approxi- mate D5h symmetry and consists of a cyclic assembly of five PW6O22 units. A sodium ion is located within the pol- yanion on the fivefold axis and 1.25 above the pseudo mir- ror plane that contains the five phosphorus atoms [17]. Preyssler polyanion as a large anion can provide many ‘‘sites’’ on the oval-shaped molecule that are likely to ren- der the catalyst effective. The Keggin anions have an assembly of 12 corner-shared octahedral MoO6 from trimetallic groups [Mo3O13] around a heteroatom tetrahedron PO4. The introduction of vana- dium (V) into theKeggin framework of [PMo12O40] 3� is ben- eficial for catalysis reactions. Usually positional isomers are possible and coexist when two or more vanadium atoms are incorporated into the Keggin structure. Studies on these iso- mers in catalytic reactions indicate that different isomers cause to show different reactivities. Yields were analyzed by GC. With respect to the catalytic performances for these cat- alysts and the overall effects of all isomers, for synthesizing Table 2 Synthesis of coumarin derivatives using H14[NaP5W30O110] under refluxing co Entry R1 R2 R3 R4 1 H H H CH2CH3 2 H H H H 3 H OCH3 H CH2CH3 4 H H NO2 H 5 CH3 H H H 6 CH3 H H CH2CH3 a Yields were analyzed by GC. Table 3 Synthesis of 3-acetyl-coumarin derivatives from reaction of 2-hydroxyl- benzaldehyde derivatives and 1-ethylacetoacetate using various hetero- polyacids under refluxing condition Entry R1 R2 R3 Catalyst Yield% a 1 H H H H14[NaP5W30O110] 98.2 2 H H H H6[P2W18O62] 95 3 H H H H5[PMo10V2O40] 92 4 H H H H4[PMo11VO40] 85.7 5 H OCH3 H H14[NaP5W30O110] 97 6 H OCH3 H H6[P2W18O62] 93 7 H OCH3 H H5[PMo10V2O40] 87 8 H OCH3 H H4[PMo11VO40] 80 9 CH3 H H H14[NaP5W30O110] 65 10 CH3 H H H6[P2W18O62] 61 and tungsten [18]. The abundance of different isomers may also play an important role in catalytic performance. ndition R5 Yield% a Mp/ref. (�C) Found Reported CH3 98.2 121 121–2 [19] OH 97 191 189–192 [20] CH3 97 174 174 [21] OH 95.7 235 234–235 [20] OH 59 161 161–2 [20] CH3 65 98 97–8 [22] can be easily removed. The ketimine product was used to Table 5 Effect of different reaction time and temperature on synthesis of 3-acetyl- coumarin derivatives from reaction of 2-hydroxyl-benzaldehyde deriva- tives and 1-ethylacetoacetate using H14[NaP5W30O110] Entry R1 R2 R3 Time (h) Yield% a 25 �C 50 �C 82 �C 1 H H H 0.5 52 60 65 2 H H H 1 71 77 82 3 H H H 1.5 77 84 90 4 H H H 2 80 93 98.2 5 H OCH3 H 0.5 51 58 62 6 H OCH3 H 1 74 80 88 7 H OCH3 H 1.5 78 85 92 8 H OCH3 H 2 88 92 97 9 CH3 H H 0.5 25 30 35 10 CH3 H H 1 35 43 48 11 CH3 H H 1.5 48 53 58 12 CH3 H H 2 55 62 65 a Yields were analyzed by GC. Communications 9 (2008) 470–474 473 In addition, different positional Mo atom(s) substituted by the V atom(s) in [PMo12O40] 3� may create different vana- dium chemical environments, thus causing these catalysts to exhibit varying catalytic performances. The yields of reaction, using Preyssler HPA is slightly higher, because the catalysts were used in mol ratio not the mol percentage of metal atoms. The efficiency of catalysts is related to the mol percent- age of metal atoms. The Preyssler HPA contain30 tugsten atoms, while the Wells–Dawson HPA has almost twice less (18) tugsten atoms, the efficiency of the Wells–Dawson HPA is thus intrinsically much better than that of the Preyssler HPA. On the other hand, the metal atoms in Keg- gin HPAs is almost three times less (12) than Preyssler HPA, So the relative efficiency of the systems vary as, Keg- gin�Wells–Dawson > Preyssler. Considering mass catalytic ratio (W = 184, Mo = 96, V = 51), it is clear that Keggin HPAs are more practical industrial efficient than others. Table 4 Synthesis of coumarin-3-carboxylic acids derivatives from reaction of 2-hydroxyl-benzaldehyde derivatives and malonic acid using various heteropolyacids under refluxing condition Entry R1 R2 R3 Catalyst Yield% a 1 H H H H14[NaP5W30O110] 97 2 H H H H6[P2W18O62] 94.8 3 H H H H5[PMo10V2O40] 92.2 4 H H H H4[PMo11VO40] 85.7 5 H H NO2 H14[NaP5W30O110] 95.7 6 H H NO2 H6[P2W18O62] 89 7 H H NO2 H5[PMo10V2O40] 84 8 H H NO2 H4[PMo11VO40] 80 9 CH3 H H H14[NaP5W30O110] 59 10 CH3 H H H6[P2W18O62] 52 11 CH3 H H H5[PMo10V2O40] 48 12 CH3 H H H4[PMo11VO40] 41 a Yields were analyzed by GC. M.M. Heravi et al. / Catalysis In order to confirm the utility of HPAs, as effective cat- alysts, these reactions were repeated in the absence of the HPAs. In all cases a mixture of reactants were recovered. The results show that in the absence of the HPAs the reaction time is much longer, and the yield of reaction is lower. For example synthesis of coumarin-3-carboxylic acid was carried out after more than 10 h and the yield of reaction was less than 90%. The effect of temperature was studied by carrying out the reactions at different temperatures [room temperature, 25 �C, 50 �C and under refluxing temperature (82 �C)]. As it shown in Tables 5 and 6 by raising the reaction temper- ature from ambient temperature (25 �C) to refluxing tem- perature (82 �C) the yield of reactions increased, but increasing the reaction temperature above the refluxing temperature had no effect on yield of reactions. From these results, it was decided that refluxing temperature would be the best temperature for all reactions. For investigation of reaction time the yield of reactions were studied at different time (0.5, 1, 1.5, 2 h). The results indicate that in each reaction, increasing the time of reac- tion from 0.5 h to 2 h increase the yield of reactions but running the reactions for more than 2 h had no effect on yield of reactions, so the best time for all reactions was optimized to be 2 h. Under the classical conditions for Knoevenagel conden- sation, we failed to prepare 4-methylcoumarin-3-carboxylic acids or 4-methyl 3-acetyl-coumarins (entries 5–6, Table 2) due to the lack of the ketone reactivity to nucleophilic attack compared to aldehydes. According to the literature, to solve this problem we pre- pared ketimine from ammonia and ketone directly [20]. Ammonia/methanol was used as the ammonia source. Under this condition ketimines can be readily formed. We use 7 M ammonia solution in methanol because it Table 6 Effect of different reaction time and temperature on synthesis coumarin-3- carboxylic acids derivatives from reaction of 2-hydroxyl-benzaldehyde derivatives and malonic acid using H14[NaP5W30O110] Entry R1 R2 R3 Time (h) Yield% a 25 �C 50 �C 82 �C 1 H H H 0.5 50 58 62 2 H H H 1 65 70 76 3 H H H 1.5 77 84 90 4 H H H 2 80 93 97 5 H H NO2 0.5 50 55 60 6 H H NO2 1 74 80 86 7 H H NO2 1.5 76 85 90 8 H H NO2 2 87 90 95.7 9 CH3 H H 0.5 18 25 30 10 CH3 H H 1 32 38 45 11 CH3 H H 1.5 38 47 54 12 CH3 H H 2 48 53 59 a Yields were analyzed by GC. Table 7 A comparison of the catalyst effects in the synthesis of coumarin-3-carboxylic acid Entry Condition Reagents Catalyst Yield% 1 Reflux in ethanol for 2 h ortho-Hydroxyary yary yary yary id a id a id a id a id a te b deh 474 M.M. Heravi et al. / Catalysis Communications 9 (2008) 470–474 react with 1-ethylacetoacetate or malonic acid in presence of catalytic amount of heteropolyacids (Scheme 2). In order to show the merit of this method for Knoevena- gel condensation, we compared our results for synthesis of coumarin-3-carboxylic acids in the presence of heteropoly- acids to those of other catalysts and reaction conditions used in previous works, such as solid phase, kaolinitic clays, EPZ10 and EPZG, solvent free and using focused microwaves (Table 7). 4. Conclusions In conclusion, we have developed a convenient method for the synthesis of coumarin-3-carboxylic acids and 3-acetyl-coumarins from ortho-hydroxyaryl aldehydes and 1-ethylacetoacetate or malonic acid in presence of catalytic amount of heteropolyacids. The advantages of this method are reusability of catalysts, easy work-up procedure and 2 Reflux in ethanol for 2 h ortho-Hydrox 3 Reflux in ethanol for 2 h ortho-Hydrox 4 Reflux in ethanol for 2 h ortho-Hydrox 5 Focused microwaves, solvent free, reaction time was 4 min [23] Meldrum’s ac 6 Focused microwaves, solvent free, reaction time was 3 min [23] Meldrum’s ac 7 Focused microwaves, solvent free, reaction time was 5 min [23] Meldrum’s ac 8 Reflux in ethanol at room temperature for 2 h [20] Meldrum’s ac 9 Reaction in water at reflux for 10 h [24] Meldrum’s ac 10 Solid phase, ethyl malonate bound to the Wang resin [25] Ethyl malona hydroxyarylal high yields. This method has been successfully modified to prepare their 4-alkyl substituted derivatives from the less reactive 1-(2-hydroxy-phenyl)-ethanone. Acknowledgment M.M.H. is thankful for the partial financial assistance from Iran presidential office Project Number 84186. References [1] R.O. Kennedy, R.D. Thornes, Coumarins: Biology, Applications and Mode of Action, John Wiley and Sons, Chichester, 1997. [2] M. Zabradnik, The Production and Application of Fluorescent Brightening Agents, John Wiley and Sons, New York, 1992. [3] M. Maeda, Laser Dyes, Academic, New York, 1994. [4] L.E. Briand, G.T. Baronelti, H.J. Thomas, Appl. Catal. A: Gen. 256 (2003) 37. [5] M.A. Schwegler, H. van Bekkum, N. Munck, Appl. Catal. 74 (1991) 191. [6] I.V. Kozhevnikov, K.I. Matveev, Appl. Catal. 5 (1983) 135. [7] I.V. Kozhevnikov, Catal. Rev.-Sci. Eng. 37 (2) (1995) 311. [8] Y. Izumi, R. Hasebe, K. Urabe, J. Catal. 84 (1983) 402. [9] H. Soeda, T. Okuhara, M. Misono, Chem. Lett. (1994) 909. [10] F.F. Bamoharram, M.M. Heravi, M. Roshani, M. Jahangir, A. Gharib, Appl. Catal. 302 (2006) 42–47. [11] M.M. Heravi, T. Benmord, K. Bakhtiari, F.F. Bamoharram, H.A. Oskooie, J. Mol. Catal. A: Chem. 264 (2006) 318–321. [12] G.T. Baronetti, L. Briand, U. Sedran, H. Thomas, Appl. Catal. A: Gen. 172 (1998) 265. [13] M.M. Heravi, F. Derikvand, L. Ranjbar, F.F. Bamoharram, J. Mol. Catal. A: Chem. 261 (2007) 56–159. [14] M.H. Alizadeh, H. Razavi, F.F. Bamoharram, K. Daneshvar, J. Mol. Catal. A: Chem. 206 (2003) 89–93. [15] M.M. Heravi, F. Derikvand, F.F. Bamoharram, J. Mol. Catal. A: Chem. 263 (2007) 112–114. [16] M.M. Heravi, Kh. Bakhtiari, N.M. Javadi, F.F. Bamoharram, M. laldehyde and malonic acid H14[NaP5W30O110] 97 laldehyde and malonic acid H6[P2W18O62] 94.8 laldehyde and malonic acid H5[PMo10V2O40] 92.2 laldehyde and malonic acid H4[PMo11VO40] 85.7 nd ortho-hydroxyarylaldehyde EPZ10 82 nd ortho-hydroxyarylaldehyde EPZG 84 nd ortho-hydroxyarylaldehyde Natural clay 71 nd ortho-hydroxyarylaldehyde Piperidinium acetate 89 nd ortho-hydroxyarylaldehyde Without using any catalyst 93 ound to the Wang resin and ortho- yde Piperidine 36 Saeedi, H.A. Oskooie, J. Mol. Catal. A: Chem. 264 (2007) 50–52. [17] M.H. Alizadeh, S.P. Harmalker, Y. Jeanenin, J. Martin-Frere, M.T. Pope, J. Am. Chem. Soc. 107 (1985) 2662. [18] I.K. Song, M.A. Barteau, J. Mol. Catal. 212 (2004) 229. [19] K.B. Rall, V.V. Perekalin, Doklady Akad. Nauk SSSR 100 (1955) 715–717. [20] A. Song, X. Wang, K.S. Lam, Tetrahedron Lett. 44 (2003) 1755–1758. [21] N.g.Ph. Buu-Hoi, T.B. Loc, Ng.D. Xuong, Bull. Soc. Chim. France (1957) 561–563. [22] P. Mastagli, N. Anderic, Comt. Rend. 246 (1958) 3079–3081. [23] B.P. Bandgar, L.S. Uppalla, D.S. Kurule, Green Chem. 1 (1999) 243–245. [24] R. Maggi, F. Bigi, S. Carloni, A. Mazzacani, G. Sartori, Green Chem. 3 (2001) 173–174. [25] B.T. Watson, G.E. Christiansen, Tetrahedron Lett. 39 (1998) 6087–6090. The synthesis of coumarin-3-carboxylic acids and 3-acetyl-coumarin derivatives using heteropolyacids as heterogeneous and recyclable catalysts Introduction Experimental Chemicals and apparatus General procedure Synthesis of coumarin-3-carboxylic acids and 3-acetyl-coumarins Synthesis of 4-methyl coumarin-3-carboxylic acids and 4-methyl 3-acetyl-coumarins Reusability of catalyst Results and discussion The structural characteristics of the catalysts are as follow Conclusions Acknowledgment References