Indian Journal of Chemistry Vol. 49B, April 2010, pp. 532-535 Note Synthesis of new isoxazolyl coumarins by eco-friendly dipyridine cobalt chloride catalyzed Pechmann reaction at ambient temperature E Rajanarendar*, Firoz Pasha Shaik & M Nagi Reddy Department of Chemistry, Kakatiya University, Warangal 506 009, India E-mail: rajanarendareligeti@gmail.com Received 30 March 2009; accepted (revised) 18 December 2009 Dipyridine cobalt chloride is used as an alternative conven- tional Lewis acid catalyst in the Pechmann condensation of iso- xazolyl phenols with β-ketoesters leading to the formation of isoxazolyl coumarins. The method is simple, cost-effective and at ambient temperature gives good yields. Keywords: Isoxazolyl phenols, β-ketoesters, isoxazolyl coumarins, dipyridine cobalt chloride. Coumarins and its derivatives are an important group of naturally occurring compounds widely distributed in the plant kingdom and occupy a special role in the realm of natural and synthetic organic chemistry. Many products that contain this sub-unit exhibit useful and diverse biological activities like anti- helmentic, hypnotic, insecticidal and antiocoagulant 1 properties and used as inhibitory of steroid 5α- reductase 2 and inhibitory of HIV-1-protease 3 . Members of this group display a broad range of applications as fragrances, pharmaceuticals and agro chemicals 4 , additives to food and cosmetics 5 , optical brightening agents 6 , dispersed florescent and tunable dye lasers 7 . Isoxazoles have been found to possess marked biological effects as CNS stimulants 8 , anti- inflammatory and analgesic 9 , antimicrobial 10 , anti- tumor 11 , chemotherapeutic agents 12 and found to possess vasodilating effect 13 similar to that of nifedipine. In view of these facts, considerable efforts have been made for the synthesis of coumarins by Pechmann 14 , Knoevenagel 15 , Reformatsky 16 and Witting 17 reactions. However, the Pechmann reaction has been the most widely applied method for preparation of coumarins as it proceeds from very simple starting materials, which involves the condensation of phenols with β-ketoesters in the presence of a variety of acidic condensing agents such as H 2 SO 4 , HCl, P 2 O 5 , POCl 3 , H 3 PO 4 and F 3 CCOOH (ref. 18). However, excess rough quantities of mineral acid are usually required in a classical preparation, which leads to the environmental pollution and also leads to the formation of undesired side products. To overcome this problem, a number of procedures were reported for synthesis of coumarins by sustainable catalytic methods, by employing montmorillonite 19 , zeolites 20 , solid acid catalysts 21 , cation exchange resins 22 , besides InCl 3 (ref.23), ZrCl 4 (ref.24), Yb(OTf) 3 (ref.25) and PTSA (ref.26). These methods have their own merits and disadvantages, therefore the introduction of efficient and new methods based on green methodology is still in demand. CoPy 2 Cl 2 is unique Lewis acid due to the presence of two electron deficient pyridine rings and also inexpensive and can be prepared in laboratory easily by heating of CoCl 2 and pyridine 27 . Very recently, the utility of CoPy 2 Cl 2 as condensing agent in the Pechmann reaction for the preparation of substituted coumarins was reported by Madhav et al. 28 In this paper, they described the synthesis of already known coumarins by conventional and microwave irradiation method by using CoPy 2 Cl 2 . In the present investigation, for the first time, we have utilized isoxazolyl substituted resorcinol derivatives in the Pechmann condensation, there by achieved the synthesis of new and rare isoxazolyl coumarins by utilizing CoPy 2 Cl 2 as the condensing agent. In a sequel to our work on isoxazoles 29 , we herein report a new efficient, mild, ecofriendly and inexpensive Pechmann reaction for the synthesis of isoxazolyl coumarins at ambient temperature by using CoPy 2 Cl 2 as Lewis acid catalyst. We predict that these isoxazolyl coumarins may be useful bioactive compounds in view of their individual biolabile nature. Results and Discussion The reaction of 3-amino-5-methylisoxazole 1 with chloro acetyl chloride in dry benzene in the presence of triethyl amine furnished N-1-(5-methyl-3- isoxazolyl)-2-chloroacetamide 2. The chloroaceta- mide 2 on treatment with resorcinol in the presence of