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Organic Chemistry International
Volume 2012 (2012), Article ID 475301, 5 pages
http://dx.doi.org/10.1155/2012/475301
Research Article

Mg(HSO4)2/SiO2 as a Highly Efficient Catalyst for the Green Preparation of 2-Aryl-1,3-Dioxalanes/Dioxanes and Linear Acetals

1Department of Chemistry, Dezful Branch, Islamic Azad University, Dezful, Iran
2Young Researchers Club, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran

Received 24 March 2012; Revised 7 May 2012; Accepted 8 May 2012

Academic Editor: Robert Engel

Copyright © 2012 Fariba Jafari and Saeed Khodabakhshi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Silica-supported magnesium hydrogen sulfate has been used as a recyclable catalyst for the synthesis of some linear and cyclic aromatic acetals under solvent-free conditions. This environmentally friendly method has advantages, such as high yield of products, simple work-up procedure, and avoidance of the organic solvents, which will contribute in serving as a green process greatly.

1. Introduction

Recently, silica supported catalysts have attracted the special attention of chemists [13] due to their eco-friendly nature, simple handling, recyclability, and high reactivity [46]. Similarly, protection of carbonyl functionaries from nucleophilic attack is one of the major problems faced during multistep syntheses. These problems remain a crucial challenge to organic chemists. A suitable method for solving this problem is the acetalization of carbonyl functions since acetals and 1,3-dioxanes are stable under neutral and basic conditions [7, 8]. Besides the interest in acetals as protecting groups, many of them can serve for fragrances in cosmetics, pharmaceuticals, detergents, lacquer industries, and applications as food and beverage additives [911].

Until now, several methods for the acetalization of the carbonyl function have been reported using ionic liquids [1215], protonic acids such as HCl and H2SO4 and Lewis acids [1619], and transitional metal complexes including Rh, Pd, and Pt [20, 21]. Some of these strategies suffer from the drawback of green chemistry, and have been associated with several shortcomings such as use of corrosive protic acids and unrecyclable catalyst, long-reaction times and low product yields, difficult work-up procedure, and the use of organic solvents. Therefore, presentation of a new, inexpensive and eco-friendly method for the protection of carbonyl functionality is an important topic, and one which is an active ongoing research area. There is a scope for the further improvement towards green reaction conditions and improved yields. We wish to report here a green and simple method for the protection of aromatic aldehydes 1 by diols 2 or aromatic alcohols 3 as 1,3-dioxanes, 1,3-dioxalanes 4, and linear acetals 5 using a catalytic quantity of silica supported magnesium hydrogen sulfate under solvent-free conditions in excellent yields (Scheme 1).

475301.sch.001
Scheme 1: Acetalization of aromatic aldehydes using Mg(HSO4)2/SiO2.

2. Results and Discussion

A solvent-free reaction reduces pollution and cost due to simplification of experimental procedure, work-up technique, and saving of labour. To exploit simple and suitable conditions for the synthesis of 4 and 5 using Mg(HSO4)2/SiO2 as an efficient solid acid catalyst, the treatment of benzaldehyde and ethanediol was chosen as a model reaction (Scheme 2). Firstly, we found that in the absence of catalyst, the reaction did not proceed even at a high temperature (25–90°C). After examining the various amounts of Mg(HSO4)2/SiO2, we found that the condensation reaction can be efficiently carried out by adding 0.2 g of the catalyst under grinding conditions at room temperature in a short time span of 10 min. The use of excessive amounts of the catalyst does not increase the yield or reaction rate (Table 1).

tab1
Table 1: Optimization of the amounts of Mg (HSO4)2/SiO2 under solvent-free conditions for the reaction of benzaldehyde with ethandiol.
475301.sch.002
Scheme 2: The reaction of benzaldehyde and ethanediol under solvent-free conditions.

After optimization, the scope of this reaction was examined using a variety of aromatic aldehydes and aromatic alcohols and diols. It was found that both electron rich and electron poor aldehydes reacted well in this process to afford the corresponding products 4 and 5 in excellent yields. The obtained results are summarized in Table 2.

tab2
Table 2: Synthesis of 4 and 5 using Mg(HSO4)2/SiO2 under solvent-free conditions.

The main advantages of the presented protocol over existing methods can be seen by comparing our results with those of some previous reported procedures, as shown in Table 3 (Scheme 3).

tab3
Table 3: Comparison of our method with previous reported method in the synthesis of 4a.
475301.sch.003
Scheme 3: The reaction of benzaldehyde and ethanediol under various conditions.

As can be concluded from Table 3, the present method is more appropriate than the others due to its excellent product yield in shorter reaction time without using organic solvents. In many cases, in order to achieve fast synthesis in an organic process, a catalyst must be used. The need to implement green chemistry principles (e.g., safer solvents, less hazardous chemical synthesis, atom economy, and catalysis) is a driving force towards the development of safe and reusable catalysts and avoidance of the use of organic solvents [2225]. In this protocol, Mg(HSO4)2/SiO2 acts as a safe, highly efficient, and recyclable catalyst under solvent-free conditions. It should be also mentioned that our efforts on the acetalization of aliphatic aldehydes and ketalization of aromatic ketones using silica supported magnesium hydrogen sulfate under similar conditions were unsuccessful. The problem with alkyl aldehydes is likely to be a result of their being enolizable. To conclude, we present a new and green method for the synthesis of 1,3-dioxanes, 1,3-dioxalanes, and linear acetals by employing silica supported magnesium hydrogen sulfate as a safe, inexpensive, and reusable solid acid catalyst under solvent-free conditions. Higher yields and shorter reaction times than the classical methods, and simple work-up procedure are the appealing attributes of this work.

3. Experimental Section

3.1. General.

Chemicals were purchased from Fluka, Merck, and Aldrich chemical companies. Yields refer to isolated pure products. The products were characterized by comparison of their spectral (IR and 1H-NMR) and physical data with authentic samples which were produced by other reported procedures.

3.2. Preparation of Silica Supported Magnesium Hydrogen sulfate

A 50 mL suction flask was equipped with a constant-pressure dropping funnel. The gas outlet was connected to a vacuum system through an adsorbing solution (water) and an alkali trap. Anhydrous magnesium chloride (4.0 g, 40 mmol) was charged in the flask and concentrated sulfuric acid (98%, 7.35 g, 40 mmol) was added dropwise over a period of 30 min at room temperature. HCl evolved immediately. After completion of the addition, the mixture was shaken for 30 min, while the residual HCl was eliminated by suction. The Mg(HSO4)2 (6.46 g) was obtained as white gel. The obtained solid acid was mixed by silica gel 40 (6.43 g).

3.3. General Procedure for the Synthesis of 4 and 5

A mixture of 1 mmol of aldehyde, 1.5 mmol of diol or 2 mmol of aromatic alcohol, and Mg(HSO4)2/SiO2 (0.2 g) was added to a mortar. The mixture was thoroughly ground with a pestle at room temperature. The progress of the reaction was monitored by TLC (EtOAc/hexane, 1 : 3). After completion of the reaction, the mixture was dissolved in CHCl3 (2 × 10 mL) and the catalyst was filtered. After evaporation of the solvent under reduced pressure and addition of ethanol and water, almost pure 4 and 5 were obtained in 90–98%. Further purification was achieved by recrystallization from the appropriate solvent. The catalyst was washed with diethyl ether, dried at 70°C for 45 min and reused in another reaction.

Acknowledgment

Financial support for this work by the research affairs, Islamic Azad University of Gachsaran, is gratefully acknowledged.

References

  1. M. A. Zolfigol, G. Chehardoli, and S. E. Mallakpour, “Silica sulfuric acid/NaNO2 as a novel heterogeneous system for the oxidation of urazoles under mild conditions,” Synthetic Communications, vol. 33, no. 5, pp. 833–841, 2003. View at Publisher · View at Google Scholar · View at Scopus
  2. G. Szöllösi, Z. Makra, F. Fülöp, and M. Bartók, “The first case of competitive heterogeneously catalyzed hydrogenation using continuous-flow fixed-bed reactor system: Hydrogenation of binary mixtures of activated ketones on Pt-alumina and on Pt-alumina-cinchonidine catalysts,” Catalysis Letters, vol. 141, no. 11, pp. 1616–1620, 2011. View at Publisher · View at Google Scholar · View at Scopus
  3. W. Gil, K. Boczoń, A. M. Trzeciak et al., “Supported N-heterocyclic carbene rhodium complexes as highly selective hydroformylation catalysts,” Journal of Molecular Catalysis A: Chemical, vol. 309, no. 1-2, pp. 131–136, 2009. View at Publisher · View at Google Scholar · View at Scopus
  4. B. Karami, V. Ghashghaee, and S. Khodabakhshi, “Novel silica tungstic acid (STA): preparation, characterization and its first catalytic application in synthesis of new benzimidazoles,” Catalysis Communications, vol. 20, pp. 71–75, 2012. View at Publisher · View at Google Scholar · View at Scopus
  5. B. Karimi and M. Khalkhali, “Silica functionalized sulfonic acid as a recyclable interphase catalyst for chemoselective thioacetalization of carbonyl compounds in water,” Journal of Molecular Catalysis A, vol. 271, no. 1-2, pp. 75–79, 2007. View at Publisher · View at Google Scholar · View at Scopus
  6. N. Fukaya, M. Ueda, S. Y. Onozawa et al., “Palladium complex catalysts immobilized on silica via a tripodal linker unit with amino groups: preparation, characterization, and application to the Suzuki-Miyaura coupling,” Journal of Molecular Catalysis A, vol. 342-343, pp. 58–66, 2011. View at Publisher · View at Google Scholar · View at Scopus
  7. M. Rahimizadeh, T. Bazazan, A. Shiri, M. Bakavoli, and H. Hassani, “Preyssler-type heteropoly acid: a new, mild and efficient catalyst for protection of carbonyl compounds,” Chinese Chemical Letters, vol. 22, no. 4, pp. 435–438, 2011. View at Publisher · View at Google Scholar · View at Scopus
  8. T. Kawabata, T. Mizugaki, K. Ebitani, and K. Kaneda, “Highly efficient heterogeneous acetalization of carbonyl compounds catalyzed by a titanium cation-exchanged montmorillonite,” Tetrahedron Letters, vol. 42, no. 47, pp. 8329–8332, 2001. View at Publisher · View at Google Scholar · View at Scopus
  9. J. H. Clark, “Solid acids for green chemistry,” Accounts of Chemical Research, vol. 35, no. 9, pp. 791–797, 2002. View at Publisher · View at Google Scholar · View at Scopus
  10. P. T. Anastas and J. B. Zimmerman, “Design through the 12 principles of green engineering,” Environmental Science and Technology, vol. 37, no. 5, pp. 94A–101A, 2003. View at Scopus
  11. A. W. Faull, A. G. Brewster, G. R. Brown, M. J. Smithers, and R. Jackson, “Dual-acting thromboxane receptor antagonist/synthase inhibitors: Synthesis and biological properties of [2-substituted-4-(3-pyridyl)-1,3-dioxan-5- yl]alkenoic acids,” Journal of Medicinal Chemistry, vol. 38, no. 4, pp. 686–694, 1995. View at Publisher · View at Google Scholar · View at Scopus
  12. J. Miao, H. Wan, Y. Shao, G. Guan, and B. Xu, “Acetalization of carbonyl compounds catalyzed by acidic ionic liquid immobilized on silica gel,” Journal of Molecular Catalysis A, vol. 348, no. 1-2, pp. 77–82, 2011. View at Publisher · View at Google Scholar · View at Scopus
  13. J. Zhang, S. Bao, and J. G. Yang, “Synthesis of a novel multi-SO3H functionalized strong Brønsted acidic ionic liquid and its catalytic activities for acetalization,” Chinese Science Bulletin, vol. 54, no. 21, pp. 3958–3964, 2009. View at Publisher · View at Google Scholar · View at Scopus
  14. D. Fang, K. Gong, Q. Shi, and Z. Liu, “A green procedure for the protection of carbonyls catalyzed by novel task-specific room-temperature ionic liquid,” Catalysis Communications, vol. 8, no. 10, pp. 1463–1466, 2007. View at Publisher · View at Google Scholar · View at Scopus
  15. D. Li, F. Shi, J. Peng, S. Guo, and Y. Deng, “Application of functional ionic liquids possessing two adjacent acid Sites for acetalization of aldehydes,” Journal of Organic Chemistry, vol. 69, no. 10, pp. 3582–3585, 2004. View at Publisher · View at Google Scholar · View at Scopus
  16. T. W. Greene, Protective Groups in Organic Synthesis, Wiley Interscience, New York, NY, USA, 1981.
  17. J. Bornstein, S. F. Bedell, P. E. Drummond, and C. L. Kosloski, “The synthesis of α-amino-o-tolualdehyde diethylacetal and its attempted conversion to pseudoisoindole,” Journal of the American Chemical Society, vol. 78, no. 1, pp. 83–86, 1956. View at Scopus
  18. B. T. Gregg, K. C. Golden, and J. F. Quinn, “Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups,” Tetrahedron, vol. 64, no. 15, pp. 3287–3295, 2008. View at Publisher · View at Google Scholar · View at Scopus
  19. S. Madabhushi, K. K. R. Mallu, N. Chinthala, C. R. Beeram, and V. S. Vangipuram, “Efficient and chemoselective acetalization and thioacetalization of carbonyls and subsequent deprotection using InF3 as a reusable catalyst,” Tetrahedron Letters, vol. 53, no. 6, pp. 697–701, 2012. View at Publisher · View at Google Scholar · View at Scopus
  20. M. Cataldo, E. Nieddu, R. Gavagnin, F. Pinna, and G. Strukul, “Hydroxy complexes of palladium(II) and platinum(II) as catalysts for the acetalization of aldehydes and ketones,” Journal of Molecular Catalysis A, vol. 142, no. 3, pp. 305–316, 1999. View at Publisher · View at Google Scholar · View at Scopus
  21. E. Nieddu, M. Cataldo, F. Pinna, and G. Strukul, “Acetalization of α,β-unsaturated carbonyl compounds catalyzed by complexes of Pt(II),” Tetrahedron Letters, vol. 40, no. 38, pp. 6987–6990, 1999. View at Publisher · View at Google Scholar · View at Scopus
  22. G. R. Najafi, “A green and efficient oxidation of benzylic alcohols using H2O2 catalyzed by Montmorillonite-K10 supported MnCl2,” Chinese Chemical Letters, vol. 21, no. 10, pp. 1162–1164, 2010. View at Publisher · View at Google Scholar · View at Scopus
  23. B. Karami, S. J. Hoseini, S. Nikoseresht, and S. Khodabakhshi, “Fe3O4 nanoparticles: a powerful and magnetically recoverable catalyst for the synthesis of novel calix[4]resorcinarenes,” Chinese Chemical Letters, vol. 23, no. 2, pp. 173–176, 2012. View at Publisher · View at Google Scholar · View at Scopus
  24. I. Mohammadpoor-Baltork, M. Moghadam, V. Mirkhani, S. Tangestaninejad, and H. Reza Tavakoli, “Highly efficient and green synthesis of 14-aryl(alkyl)-14H-dibenzo[a,j] xanthene and 1,8-dioxooctahydroxanthene derivatives catalyzed by reusable zirconyl triflate [ZrO(OTf)2] under solvent-free conditions,” Chinese Chemical Letters, vol. 22, no. 1, pp. 9–12, 2011. View at Publisher · View at Google Scholar · View at Scopus
  25. H. Eshghi, M. Rahimizadeh, and S. Saberi, “Fe(HSO4)3 as an inexpensive, eco-friendly, heterogeneous and reusable catalyst for acetal/ketal formation and their facile regeneration,” Catalysis Communications, vol. 9, no. 14, pp. 2460–2466, 2008. View at Publisher · View at Google Scholar · View at Scopus
  26. M. Moghadam, I. Mohammadpoor-Baltork, S. Tangestaninejad, V. Mirkhani, P. Yazdani, and S. Ghorjipoor, “Highly efficient and chemoselective acetalization of carbonyl compounds catalyzed by new and reusab e zirconyl triflate, ZrO(OTf)2,” Heteroatom Chemistry, vol. 20, no. 3, pp. 131–135, 2009. View at Publisher · View at Google Scholar · View at Scopus
  27. H. Firouzabadi, N. Iranpoor, and B. Karimi, “Zirconium tetrachloride (ZrCl4) catalyzed highly chemoselective and efficient acetalization of carbonyl compounds,” Synlett, no. 3, pp. 321–323, 1999. View at Scopus
  28. B. B. F. Mirjalili, M. A. Zolfigol, A. Bamoniri, and A. Hazar, “Acetalization of carbonyl compounds by using silica-bound sulfuric acid under green condition,” Bulletin of the Korean Chemical Society, vol. 25, no. 6, pp. 865–868, 2004. View at Scopus