Synthesis of amidoalkyl naphthols by nano-Fe 3 O 4 modified carbon nanotubes via a multicomponent strategy in the presence of microwaves Javad Safari *, Zohre Zarnegar Laboratory of Organic Compound Research, Department of Organic Chemistry, College of Chemistry, University of Kashan, P.O. Box 87317-51167, Kashan, IR, Iran 1. Introduction Multicomponent reactions (MCRs) are of increasing importance in organic synthesis [1–5] as they can produce target products in a single operation without isolating the intermediates and therefore reducing the reaction times and energy input [6,7]. In MCR strategies, three or more reactants come together in a single reaction vessel to form new products that contain portions of all the components. The search and discovery for new MCRs is still in demand as the best tools in combinatorial chemistry [8–11]. One of these MCRs is the preparation of amidoalkyl naphthol derivatives. 1-Amidoalkyl-2-naphthols are significant as they can be easily converted to 1-aminoalkyl-2-naphthols as an important class of biological building blocks, by amide hydrolysis reaction. 1- Aminoalkyl-2-naphthols have been applied as hypotensive and bradycardiac agents [12,13]. 1-Amidoalkyl-2-naphthols can be also converted to 1,3-oxazines [14] with potentially different biological activities such as antibiotic [15], analgesic [16], antitumor [17], anticonvulsant [18], antihypertensive [19], and antirheumatic properties [20]. In view of these useful properties, the development of new methods for the preparation of amidoalkyl naphthols is a considerable synthetic importance. The importance of amidoalkyl naphthols for their synthesis has attracted renewed attention and various improved methods have been reported [21–28]. These reported procedures mainly include the one-pot three-component condensation of aryl aldehydes, b- naphthol, and amide derivatives or acetonitrile, which employs catalysts such as 1-hexanesulphonic acid sodium [20], I 2 [21], Yb(OTf) 3 [22], Sr(OTf) 2 [23], p-TSA [24], sulfamic acid [25], ferric(III) hydrogensulfate [26], SiO 2 –HClO 4 [27], and silica sulfuric acid [28]. Most of these methods suffer from drawbacks including unsatisfactory yields, long reaction times, expensive reagent, toxic and corrosive solvent, high catalyst loading, strongly acidic conditions, and the production of environmental pollutants. On the other hand, aliphatic aldehydes did not give satisfactory yields in earlier reports. Niralwad et al. synthesized amidoalkyl naphthols in high yields in the presence of 1-hexanesulphonic acid sodium salt as catalyst under solvent-free conditions and microwave- irradiation. They also examined the reaction with aliphatic aldehydes but the yield was low as compared to aromatic aldehydes [20]. Therefore, the development of new methodology and high yielding catalytic process is desired that could overcome the above drawbacks. Magnetic nanoparticles (MNPs) have emerged as a new class of nanocatalyst for organic reactions. An important feature of these nanocatalysts is simple separation of them using an external magnet without filtration [29–31]. However, magnetic nanopar- ticles are very easy to aggregate into larger clusters owing to anisotropic dipolar attraction, losing the dispersibility and specific Journal of Industrial and Engineering Chemistry 20 (2014) 2292–2297 A R T I C L E I N F O Article history: Received 14 July 2013 Accepted 1 October 2013 Available online 14 October 2013 Keywords: Amidoalkyl naphthols Microwave-irradiation Fe 3 O 4 -CNTs Multi-component reaction Solvent-free A B S T R A C T Fe 3 O 4 -CNTs composites are synthesized using simple chemical coprecipitation which is confirmed with XRD, VSM, TEM and EDS. Fe 3 O 4 -CNTs as a magnetically active catalyst catalyze one-pot multicomponent condensation of b-naphthol with aromatic and aliphatic aldehydes and amide derivatives under solvent- free conditions and microwave-irradiation to afford the corresponding amidoalkyl naphthols in excellent yields. This catalyst provides clean conversion; greater selectivity and easy workup make this protocol practical and economically attractive. ß 2013 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. * Corresponding author. Tel.: +98 3615912320; fax: +98 361 5912397. E-mail addresses: Safari@kashanu.ac.ir, safari_jav@yahoo.com (J. Safari), z_zarnegar@yahoo.com (Z. Zarnegar). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry jou r n al h o mep ag e: w ww .elsevier .co m /loc ate/jiec 1226-086X/$ – see front matter ß 2013 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry. http://dx.doi.org/10.1016/j.jiec.2013.10.004 Downloaded from http://www.elearnica.ir