A novel protocol for solvent-free synthesis of 4,6-diaryl-3, 4-dihydropyrimidine-2(1H)-ones catalyzed by metal oxide–MWCNTs nanocomposites Javad Safari ⇑ , Soheila Gandomi-Ravandi Laboratory of Organic Compound Research, Department of Organic Chemistry, College of Chemistry, University of Kashan, P.O. Box: 87317-51167, Kashan, Islamic Republic of Iran highlights  Easy reaction condition, recyclable green catalyst and reduced environmental impacts.  The catalyst has high activity, selectivity, reusability, reasonable cost and long lifetime.  TiO 2 –MWCNTs catalyst is significantly more effective than other acid catalysts in the Biginelli-like reaction. article info Article history: Received 15 January 2014 Received in revised form 18 March 2014 Accepted 5 May 2014 Available online 29 May 2014 Keywords: Nanocomposites TiO 2 –MWCNTs Heterocycle Heterogeneous catalyst Pyrimidinone abstract A Biginelli-like condensation is described using acetophenone as active methylene compound with alde- hydes and urea to furnish pyrimidinone analogues under solvent-free conditions. In this paper, besides the preparation of nanocomposites based on MWCNTs, our investigations have been focused on the cat- alytic efficiency of metal oxide–MWCNTs composites. The requisites of a good catalyst are high activity, selectivity, reusability, reasonable cost and long lifetime. The application of solvent-free conditions and transition metal oxides decorated–MWCNTs (MO x –MWCNTs) nanocomposites as attractive, effective and reusable catalysts leads to the efficient synthesis of 4,6-diaryl-3,4-dihydropyrimidin-2-(1H)-ones. This recyclable heterogeneous catalytic system provides a simple strategy to generate a variety of pyrimidinones under solvent-free conditions. Utilization of easy reaction condition, recyclable green catalyst, reduced environmental impacts and simple work-up make this methodology as an interesting option for the eco-friendly synthesis of Biginelli-like compounds. Ó 2014 Elsevier B.V. All rights reserved. Introduction Nitrogen heterocyclic compounds have attracted considerable attention to design biologically active molecules, because their structural subunits exist in many natural products as well as phar- maceuticals [1]. Pyrimidine moiety is an important class of hetero- cycles including nitrogen and is responsible for the properties of many pharmaceutically significant natural products and synthetic compounds [2]. The pyrimidine ring is a key structural moiety of a series of natural compounds (antibiotics, nucleic acids, hormones, alkaloids and vitamin B 1 ) [3,4], life-supporting substances (vita- mins, coenzymes and uric acid) [5], synthetic medicines (Veronal, Sulfadiazine, Fluorouracil, Glivec, Rosuvastatin and barbiturates) [3,5], chemotherapeutic drugs (fluorouracil) [3], herbicides, dyes and many more compounds [4]. Preparation of these non-planar dihydropyrimidinones (DHPMs) is now recognized as a powerful heterocyclic synthesis with many important applications and it has been the subject of several reviews [3,6–8]. With regard to the pharmacological profile and medicinal applications of func- tionalized dihydropyrimidinones and -thiones, Biginelli reaction has received renewed interest to synthesize these compounds and this cyclocondensation process was enlarged by the variation of CH-acidic carbonyl compound building blocks [9]. Very recently, simple alkyl acetoacetates are employed as the active methylene building blocks for novel synthesis of Biginelli-like scaffold [7], but other types of 3-oxoalkanoic esters, benzoylacetic esters or thi- oesters can also be used successfully [6]. Moreover, cycloalkanones [10], b-keto carboxylic acid [11], cyclic ketones and substituted a-keto acids [12] or acyclic and cyclic ketones [13] can be used instead of esters to produce pyrimidinones. Also, primary, second- ary and tertiary acetoacetamides [6] and nitroacetone [14] serve as viable substrates and good building blocks. In addition, condensa- tions can be achieved by employing b-diketones, cyclic b-diketones http://dx.doi.org/10.1016/j.molstruc.2014.05.012 0022-2860/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +98 (0)361 591 2320; fax: +98 (0)361 591 2397. E-mail address: Safari@kashanu.ac.ir (J. Safari). Journal of Molecular Structure 1074 (2014) 71–78 Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc