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[a,j]xanthenes

Abstract: In this work, the efficiency, generality and applicability of novel Brønsted 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 β-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°C), and (iii) the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes from β-naphthol (2 equiv.) and aldehydes (1 equiv.) in harsh conditions (120°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. [Copyright &y& Elsevier]