MgO Nanoparticle-Catalyzed Synthesis and Broad-Spectrum Antibacterial Activity of Imidazolidine- and Tetrahydropyrimidine-2-Thione Derivatives Hamid Beyzaei 1 & Somaye Kooshki 1 & Reza Aryan 1 & Mohammad Mehdi Zahedi 2 & Alireza Samzadeh-Kermani 1 & Behzad Ghasemi 3 & Mohammadreza Moghaddam-Manesh 4 Received: 11 April 2017 /Accepted: 20 June 2017 # Springer Science+Business Media, LLC 2017 Abstract The biological properties of imidazolidine- and tetrahydropyrimidine-2-thione de- rivatives such as antiviral, antitumor, anti-inflammatory, and analgesic activities increase the demand for mild and efficient synthetic routes. In this regard, methods such as reaction of diaminoalkanes with carbon disulfide have been developed. However, this method usually suffers from relatively long reaction times, using excess reagents, vigorous reaction conditions, and emission of pernicious hydrogen sulfide gas. In this project, MgO nanoparticle was used as an efficient, non-toxic, recyclable, and economic catalyst to synthesize cyclic five- or six- membered thioureas 3a–h via reaction of 1:1 molar ratios of 1,2- or 1,3-diaminoalkanes 1a–h and carbon disulfide in ethanol at ambient temperature. More interestingly, no hydrogen sulfide emission was detected during the reaction progress. The in vitro antimicrobial proper- ties of synthesized compounds were investigated against 14 different Gram-positive and Gram-negative pathogenic bacteria according to CLSI (Clinical and Laboratory Standards Institute) broth microdilution and disk diffusion methods. The results were compared to those of penicillin, gentamicin, and ceftriaxone, and reported as inhibition zone diameter (IZD), the minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC) values. The best inhibitory effects were observed with imidazolidine-2-thiones 3c and 3d. Appl Biochem Biotechnol DOI 10.1007/s12010-017-2544-y * Hamid Beyzaei hbeyzaei@yahoo.com; hbeyzaei@uoz.ac.ir 1 Department of Chemistry, Faculty of Science, University of Zabol, Zabol 98613-35856, Iran 2 Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, SK S7N 5C9, Canada 3 Young Researchers and Elite Club, Neyshabur Branch, Islamic Azad University, Neyshabur, Iran 4 Young Researchers and Elite Club, Kerman Branch, Islamic Azad University, Kerman, Iran