Journal of Molecular Catalysis A: Chemical 291 (2008) 22–29 Contents lists available at ScienceDirect Journal of Molecular Catalysis A: Chemical journal homepage: www.elsevier.com/locate/molcata Single step synthesis of coumarin derivatives over Al-MCM-41 and its supported catalysts under solvent-free condition S. Sudha, K. Venkatachalam, S. Vishnu Priya, J. Herbert Mabel, M. Palanichamy, V. Murugesan ∗ Department of Chemistry, Anna University, Sardar Patel Road, Guindy Campus, Chennai 600025, India article info Article history: Received 20 January 2008 Received in revised form 9 April 2008 Accepted 30 April 2008 Available online 4 May 2008 Keywords: PW/Al-MCM-41 Pechmann condensation Coumarin Resorcinol Ethyl acetoacetate abstract Al-MCM-41 (Mobil Composition Mater) (Si/Al = 25) molecular sieve was synthesized hydrothermally and 20 and 40wt% phosphotungstic acid (PW) was supported on it. The materials were characterized using XRD, pyridine adsorbed FT-IR, 31 P and 1 H MAS NMR techniques. Catalytic performance of the materials was examined in the liquid phase condensation of resorcinol and ethyl acetoacetate. 7-Hydroxy- 4-methylcoumarin was the only product observed in this reaction. The results revealed that 20wt% PW/Al-MCM-41 is found to be more active than other catalysts. The reaction parameters were optimized to obtain high selectivity of the desired product at maximum resorcinol conversion. The reaction was also performed with substituted phenolic derivatives and ethyl acetoacetate in order to realize the substituent effect. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Coumarin and its derivatives have been attracting great interest because they occupy a special place in the realm of natural products and synthetic organic chemistry. Many products, which contain the subunit of coumarin, exhibit useful and diverse biological activ- ity such as molluscacides, anthelmintic, hypnotic, etc. or serve as anticoagulant agents and fluorescent brighteners [1–3]. Coumarin derivatives also find applications in pharmaceutical, fragrance and agrochemical industries [4]. 7-Hydroxy-4-methylcoumarin acts as a starting material in the preparation of hymecromone insec- ticide. Pechmann reaction is the most widely used method for preparing coumarins since it starts from simple starting materi- als and offers high yield. Mineral acids like H 2 SO 4 , HCl and H 3 PO 4 , CF 3 COOH and Lewis acids such as ZnCl 2 , FeCl 3 , SnCl 4 , TiCl 4 and AlCl 3 were used as catalysts in the conventional coumarin synthesis [5]. However, this method suffers due to formation of unnecessary by-products, long reaction time and corrosion of equipments. To avoid such problems, there have been efforts to find environmen- tally benign alternative and heterogeneously catalysed synthetic routes. The use of heterogeneous acid catalysts offers advantages like ease of operation conditions, reduced equipment corrosion and minimized contamination of waste streams combined with ∗ Corresponding author. Tel.: +91 44 22203144; fax: +91 44 22200660. E-mail address: v murugu@hotmail.com (V. Murugesan). reusability. Nafion-H, zeolite , Amberlyst 15 and other solid acids have been employed as catalyst in the Pechmann reaction [3,4,6]. Gunnewegh et al. [4] first reported Pechmann condensation of resorcinol and ethyl acetoacetate over zeolite H in toluene to obtain 7-hydroxy-4-methylcoumarin. In the case of Amberlyst 15, special equipment such as microwave oven was used for acceler- ating this reaction [7]. Potdar et al. [8] reported the synthesis of 7-hydroxy-4-methylcoumarin over neutral ionic liquids ([bmim] PF 6 /POCl 3 ) but it required hazardous POCl 3 . Al-MCM-41 (Mobil Composition Mater) with different Si/Al ratios was used as effi- cient catalysts for a variety of organic reactions [9]. They are economical and harmless catalysts, which can be filtered easily from the reaction mixture and reused. Al-MCM-41 molecular sieves have already been proved to be an effective catalyst for alkylation and acylation reactions [10–12]. The present study describes an ecofriendly procedure for the synthesis of coumarin derivative over Al-MCM-41 (Si/Al = 25) and 20 and 40 wt% PW (phosphotungstic acid) supported Al-MCM-41 (Si/Al = 25) catalysts under solvent- free condition. 2. Experimental 2.1. Catalyst preparation All reagents viz., sodium metasilicate, aluminum sulphate, cetyltrimethyl ammonium bromide (CTAB), sulfuric acid, resorci- nol and ethyl acetoacetate were purchased from Merck and used 1381-1169/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2008.04.021