Journal of Molecular Catalysis A: Chemical 353–354 (2012) 44–49 Contents lists available at SciVerse ScienceDirect Journal of Molecular Catalysis A: Chemical jou rn al h om epa ge: www.elsevier.com/locate/molcata Silica gel supported –SO 3 H functionalised benzimidazolium based ionic liquid as a mild and effective catalyst for rapid synthesis of 1-amidoalkyl naphthols Deepali A. Kotadia, Saurabh S. Soni ∗ Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar 388120, Gujarat, India a r t i c l e i n f o Article history: Received 13 July 2011 Received in revised form 11 October 2011 Accepted 1 November 2011 Available online 7 November 2011 Keywords: Silica supported ionic liquid Benzimidazolium ionic liquid 1-Amidoalkyl naphthol Multicomponent reaction One pot solvent free synthesis a b s t r a c t The use of ionic liquid in catalysis is attracting more and more attention in the field of chemistry. In line with the research we have studied Supported Ionic Liquid Catalyst (SILC) which consist of benzimida- zolium based ionic liquid immobilized on silica based solid support. The SILC proved to be an efficient heterogeneous catalyst for solvent less synthesis of 1-amidoalkyl naphthols from 2-naphthol, amides and aldehydes. The process represents a simple, ecologically safer, cost effective route to 1-amidoalkyl naphthol with high product quality, as well as easy product recovery and catalyst recycling. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Devising reactions that achieve multi-bond formation in one- operation is becoming one of the major challenges in step economic process. Multicomponent reactions (MCRs) have emerged as an important tool for building of diverse and complex organic molecules through carbon–carbon and carbon–heteroatom bond formations taking place in tandem manner [1–4]. o-Quinone methides (o-QMs) have emerged as interesting molecules due to their toxicological properties against both normal and cancerous cells and also proposed intermediary in the formation of many bio- logically important polymers [5]. o-QMs also act as intermediates for the synthesis of antitumor agents [6]. One of the tandem reac- tions which involves the in situ generation of o-QMs and its reaction with acetamide or benzamide gives amidoalkyl naphthols [7]. 1- Amidoalkyl naphthols can be easily hydrolysed to 1-aminoalkyl naphthol, which shows biological activities like depressor and brady-cardiac effect [8,9]. This 1-aminoalkyl alcohol-type ligand has been used for asymmetric synthesis and also as a catalyst [10,11]. Amidoalkyl naphthols can be prepared by the multicom- ponent condensation of aldehydes, 2-naphthols and amides using different catalysts such as Montmorillonite K10 [12], p-TSA [7], I 2 [13], K 5 CoW 12 O 40 ·3H 2 O [14], HClO 4 –SiO 2 [15], Fe(HSO 4 ) 3 [16], FeCl 3 –SiO 2 [17], BAIL [18,19], P 2 O 5 [20], cyanuric chloride [21], ∗ Corresponding author. Tel.: +91 2692 226857x219. E-mail address: soni b21@yahoo.co.in (S.S. Soni). thiamine hydrochloride [22], trityl chloride [23], [FemSILP] l- prolinate [24], silica sulphuric acid [25,26], 1-hexane sulphonic acid sodium salt [27], Zwitterionic-type molten salt [28]. However, some of these reported procedures suffer from one or more draw- backs such as long reaction times, high temperatures, low yields of products, use of toxic organic solvents, use of expensive metal salts as catalysts and tedious work up procedures. Therefore, there is still an increasing interest in catalytic system for the synthesis of 1-amidoalkyl naphthols. In recent years, ionic liquids (ILs) have become powerful alter- natives to conventional molecular organic solvents due to their particular properties, such as undetectable vapour pressure and the ability to dissolve many organic and inorganic substances [29]. In addition, ILs are readily recycled and tuneable to specific chemical tasks. One type is Bronsted acidic ILs (BAILs). The acidic nature of these ILs as catalyst has been exploited for many other important organic reactions, which proceed with excellent yields and selec- tivities and demonstrate the great potential of these ILs in catalytic technologies for chemical production [30–34]. Recently, immobilization process involving acidic ILs on solid supports has been designed. The heterogenization of catalysts and reagents can offer important advantages in handling, separation and reuse procedures. Based on economic criteria, it is desirable to minimize the amount of IL utilized in a potential process. Immo- bilized acidic ILs have been used as novel solid catalysts for many acid catalysed reactions such as esterification, nitration reaction and acetal formation [35,36]. On the other hand examples for the synthesis of amidoalkyl naphthol using efficient heterogeneous 1381-1169/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2011.11.003