SULFONATED ORDERED NANOPOROUS CARBON AS AN EFICIENT SOLID CATALYST FOR THE SYNTHESIS OF PERIMIDINE DERIVATIVES

Abstract

Sulfonated ordered nanoporous carbon (CMK-5-SO 3 H) efciently catalyzes the synthesis of perimidines using cyclocondensation of various aldehydes and ketones with 1,8-diaminonaphthalene in ethanol as a solvent at room temperature. This catalyst can be recovered and reused without significant loss of activity. This methodology provides a simple synthetic route to interesting classes of heterocycles in excellent yields at short time. Key word: sulfonated ordered nanoporous carbon, heterogeneous catalyst, perimidine, aldehyde, ketone, 1,8-diaminonaphthalene. 1 . Numbers of methods have been developed for the synthesis of perimidines involving the condensation of 1,8-diaminonaphthalene with various carbonyl compounds 2-10 . Despite efficiency of several published methods, some of these procedures suffer from disadvantages such as long reaction time, use of non reusable catalyst and limitation in the use of ketone as a substrate. Therefore, it seems that there is much room for the development of new protocols to overcome these problems. The use of heterogeneous solid catalysts in the organic synthesis and industrial reactions is interesting due to their suitable acidity, thermal stability, selectivity and reusability; they also provide a green alternative to homogeneous catalysts 11 . Among the diferent types of heterogeneous catalysts, recently, Wang and his co-workers prepared a novel sulfonic functionalized ordered mesoporous carbon (CMK-5-SO 3 H) that has high surface area, high loading and uniform nanostructure 12 . However, to the best of our knowledge, there is no report available on the synthesis of perimidine derivatives using CMK-5-SO 3 H catalysts in the open literature. Herein, we report a simple, convenient, and efficient method for the synthesis of perimidine derivatives by cyclocondensation of various aldehydes and ketones with 1, 8-diaminonaphthalene in the presence of CMK-5-SO 3 H as a reusable and eco-friendly catalyst (Scheme 1). composite was filtrated and washed with EtOH and acetone to remove excess and unpolymerized FA. The obtained composite was heated to 850 °C under vacuum at a ramp of 10 °C/min for 3 h to carbonization. Ordered mesoporous carbon (CMK-5) was obtained by removal of silica by HF (10 % in 1 : 1 EtOH - H 2 O), washed with copious water and EtOH, and dried at 100 °C. For the sulfonation of CMK-5, initially 4-benzenediazoniumsulfonate was synthesized by diazotization of p-sulfanilic acid. Solution of NaNO 2 (1 M) was slowly added to a mixture of 12.99 g of p- sulfanilic acid (0.075 mol) and 7.5 g HCl (1 M) at 3-5°C in order to option the clear solution and then the mixture was stirred for 45 min. The white precipitate formed was filtered off, washed by cold water, and dried under reduced pressure. In a typical modification, 1.2 g of CMK-5 was added in a mixture of 12.0 g of 4-benzenediazoniumsulfonate, 200 ml of distilled water and 200 ml of ethanol. Subsequently, the mixture was cooled down to 5 °C and 200 ml of 50 wt % H 3 PO 2 aqueous solution was added. After stirring for 30 min, another 200 ml of H 3 PO 2 aqueous solution was added and stirred at 5 °C for 30 min. Finally CMK-5-SO 3 H was filtered off, washed with distilled water and acetone, and dried in an oven at 80 °C. The amount of acid in CMK-5-SO 3 H was determined by thermogravimetric analysis (TGA) and ion-exchange pH analysis. Typically a loading of ca. 0.84 mmol/g was obtained. 1. 2 General procedure for the synthesis of perimidines A mixture containing 1,8-diaminonaphthalene (1.0 mmol), carbonyl compound (1.0 mmol) and CMK-5-SO 3 H (0.011 g: 1 mol%) in ethanol (3 mL) was stirred at room temperature for the appropriate time according to Table 2. (The progress of reaction was monitored by TLC). After completion of the reaction, catalyst was separated by filtration. Then water was added to the filtrate (3-5 mL) and the mixture was filtered and the precipitate washed with water and dried. The structure of products was characterized by spectral data (1H NMR and 13C NMR) and physical properties and comparison with