Ionic liquid triethylamine-bonded sulfonic acid {[Et3N-SO3H]Cl) as a novel, highly efficient and homogeneous catalyst for the synthesis of β-acetamido ketones, 1,8-dioxo-octahydroxanthenes and 14-aryl-14H-dibenzo[aj]xanthenes

In this work, the efficiency, generality and applicability of novel Bronsted acidic ionic liquid triethylamine-bonded sulfonic acid {[Et3N-SO3H]Cl, N,N-diethyl-N-sulfoethanammonium chloride} as homogeneous and green catalyst for organic transformations under various conditions are studied. Herein, the following one-pot multi-component reactions in the presence of ({[Et3N-SO3H]Cl are investigated: (i) the synthesis of beta-acetamido ketones from acetophenones, aldehydes, acetonitrile and acetyl chloride in solution and under extremely mild conditions (room temperature), (ii) the preparation of 1,8-dioxo-octahydroxanthenes from dimedone (5,5-dimethyl-1,3-cyclohexanedione) (2 equiv.) and aldehydes (1 equiv.) under solvent-free conditions at moderate temperature (80 degrees C), and (iii) the synthesis of 14-aryl-14H-dibenzo[aj]xanthenes from beta-naphthol (2 equiv.) and aldehydes (1 equiv.) in harsh conditions (120 degrees C) in the absence of solvent. High yields, relatively short reaction times, efficiency, generality, clean process, simple methodology, low cost, easy work-up, ease of preparation and regeneration of the catalyst and green conditions (in the synthesis of the xanthene derivatives) are advantages of the application of [Et3N-SO3H]Cl as catalyst in the above organic reactions. This work is the first report of the ionic liquid. (C) 2011 Elsevier B.V. All rights reserved.