ORIGINAL PAPER The first catalytic application of oxidized carbon nanotubes in a four-component synthesis of fused heterocycles Saeed Khodabakhshi 1 • Alimorad Rashidi 2 • Ziba Tavakoli 3 • Mojtaba Baghernejad 4 • Amir Yadegari 1 Received: 2 May 2015 / Accepted: 6 July 2015 Ó Springer-Verlag Wien 2015 Abstract Multiwalled carbon nanotubes were oxidized and then utilized as new heterogeneous nanocatalyst for the efficient one-pot, four-component synthesis of pyra- zolopyranopyrimidinones. This present strategy offers important advantages in terms of its simplicity, low cata- lyst loadings, catalyst recyclability, high product yields, and non-toxic nature. Graphical Abstract NH HN O HN N Ar O O Me HN N H O O O Me EtO O O NH 2 NH 2 Ar H O + OMWCNTs Keywords Multiwalled carbon nanotubes  Green  Nanocatalyst  Pyrazolopyranopyrimidinone  Heterogeneous Introduction Sustainable chemistry emphasizes on the use of catalysts with specific properties such as high activity, cost-effective prepa- ration, high stability and safety, and good recyclability [1, 2]. Findings from several recent studies show that carbon nano- materials having graphitic structures such as graphene and nanotubes (CNTs) have attracted the interest of researchers in a plethora of fields because of their significant features including electrical/thermal conductivity, excellent chemical stability, adequate surface area, and also controlled porosity [3–5]. However, the pristine multiwalled carbon nanotubes (MWCNTs) are inactive under normal conditions and they precipitate in most common solvent. Hence, the surface modification of CNTs through functionalization is particu- larly important in order to increase their dispersion or solubility. The oxidation or modification of the carbon nan- otubes can be performed using multiple oxidative agents [6]. In organic chemistry and pharmaceutical researches, heterocyclic compounds such as pyrazol, pyran, and pyrimidine derivatives have attracted widespread attention because of their biological effects [7–9]. Recently, synthesis of fused heterocycles through multicomponent strategies has been widely studied [10]. In fact, multicomponent reactions (MCRs) receive increasing attention because of their con- vergence, high stereoselectivity, and atom economy and they include relatively simple procedures which often lead to biologically important compounds in one pot. Employing such strategies will be accompanied with the minimization of both waste production and expenditure of human labor [11]. Electronic supplementary material The online version of this article (doi:10.1007/s00706-015-1532-6) contains supplementary material, which is available to authorized users. & Saeed Khodabakhshi saeidkhm@yahoo.com 1 Young Researchers and Elite Club, Robatkarim Branch, Islamic Azad University, Robatkarim, Iran 2 Nanotechnology Research Center, Research Institute of Petroleum Industry, Tehran, Iran 3 Department of Chemistry, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran 4 Young Researchers and Elite Club, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran 123 Monatsh Chem DOI 10.1007/s00706-015-1532-6