Pyridinium-N-sulfonic acid hydrogen sulfate as a highly effective and dualfunctional catalyst for the synthesis of 1-carbamatoalkyl-2-naphthols

Carbamate skeleton is significant moiety of several natural products and versatile precursors for synthesis of pharmaceutics such as saxitoxin, mitomycin and bleomycin. Compounds which have both carbamate and a hydroxyl group such as 1- carbamatoalkyl-2-naphthols are of considerable interest, because hydrolysis of carbamates can produce a variety of amino alcohols; these compounds are the main sub-structure of a variety of biologically important natural products and potent drugs including a number of nucleoside antibiotics and HIV protease inhibitors, such as ritonavir and lipinavir [1, 2]. Ionic liquids have various (ILs) unique properties, including non-flammability, nonvolatility, high thermal and chemical stability and enhanced reactivity. Brønsted acidic ILs are an important class of these compounds, which have been widely applied asefficient catalysts for organic transformations [3]. In this work protic acidic ionic liquid pyridinium N-sulfonic acid hydrogen sulfate {[Py- SO3H][HSO4]} has been used as a highly effective and homogeneous catalyst for the one-pot multi-component reaction of arylaldehydes, 2-naphthol and alkyl carbamates under solvent-free conditions to synthesize 1-carbamatoalkyl-2-naphthols (Scheme 1). Excellent yields, short reaction times, easy work-up and purification of the products, easy production of the catalyst and relatively mild conditions are some advantages of this procedure. High effectuality of [Py-SO3H][HSO4] can be attributed to its dual-functionality.