Nickel oxide nanoparticles as an efficient catalyst for one-pot synthesis of 1-amidoalkyl-2-naphthol derivatives

1-amidoalkyl-2-naphthols and their derivatives bearing 1,3-amino oxygenated functional groups are the key intermediate in number of natural products and synthetic pharmaceuticals and act as potential drugs in number of nucleoside antibiotics and HIV protease inhibitors. In addition, they also shows potential biological activities, such as antibiotic, anticonvulsant, antimalarial, antihypertensive, antitumor, antirheumatic, analgesic, antipsychotic, antianginal. Owing to their unique biological profile, synthesis of 1-Amidoalkyl-2-naphthols and their derivatives is of prime task for the organic chemist. The synthesis of 1-amidoalkyl-2-naphthols has been carried out by multi-component condensation reaction of 2-naphthol, aromatic aldehydes, and acetonitrile or various amides in the presence of different catalysts [1,2]. In modern science, one of the growing and important fields is nanotechnology. Because of different physical and chemical properties of nano-sized catalysts in comparison with bulk material, they attract interest from different researcher areas. Since the particles are in small size, the surface area exposed to the reactant is maximized, thus allowing more reactions to occur at the same time; hence, the process is speeded up. Among various metal nanostructures, nickel oxide nanoparticles have been employed as heterogeneous catalysts for various organic transformations. An increasing number of examples are available in the literature where Nickel-based nanoparticles have been used as catalysts during organic transformations [3,4]. Since these nanoparticles are often recovered easily by simple workup, which prevent contamination of products, they may be considered as promising, safe, and reusable catalysts compared to traditional catalysts. In this work, an efficient catalytic protocol for the synthesis of 1-amidoalkyl-2-naphthol derivatives is developed in a one-pot three-component approach involving β-naphthol, aromatic aldehydes and urea under microwave irradiation in solvent free condition (scheme 1). The advantageous features of this methodology are operational simplicity, high yield processing, and easy handling.