Synthesis, crystal structures and theoretical calculations of new 1-[2-(5-chloro-2-benzoxazolinone-3-yl)acetyl]-3,5-diphenyl-4,5-dihydro-(1H)- pyrazoles Umut Salgın Göks ßen a,b , Yelda Bingöl Alpaslan c,⇑ , Nesrin Gökhan Kelekçi b ,S ßamil Is ßık d , Melike Ekizog ˘lu e a Turkish Medicines and Medical Devices Agency, Analyses and Control Laboratories, 06100 Ankara, Turkey b Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Chemistry, 06100 Sıhhiye, Ankara, Turkey c Giresun University, Faculty of Medicine, Department of Biophysics, 28100 Giresun, Turkey d Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139 Kurupelit, Samsun, Turkey e Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Microbiology, 06100 Sıhhiye, Ankara, Turkey highlights " We report the synthesis of three new 2-pyrazolines. " These compounds were characterized by 1 H NMR, IR and X-ray crystallography. " The theoretical calculations were performed by DFT method. " The theoretical results were compared with experimental results. article info Article history: Received 30 August 2012 Received in revised form 25 January 2013 Accepted 26 January 2013 Available online 1 February 2013 Keywords: 5-Chloro-2-benzoxazolinone 4,5-Dihydro-(1H)-pyrazole Crystal structure DFT calculations Antimicrobial activity abstract 1-[2-(5-Chloro-2-benzoxazolinone-3-yl)acetyl]-3-phenyl-5-(3-methoxyphenyl)-4,5-dihydro-(1H)-pyrazole (5a), 1-[2-(5-chloro-2-benzoxazolinone-3-yl)acetyl]-3-phenyl-5-(3,4-dimethoxyphenyl)-4,5-dihydro- (1H)-pyrazole (5b) and 1-[2-(5-chloro-2-benzoxazolinone-3-yl)acetyl]-3-(4-methylphenyl)-5-(2,3-dime- thoxyphenyl)-4,5-dihydro-(1H)-pyrazole (5c) were synthesized. The crystal and molecular structures of the compounds 5a, 5b and 5c were determined by elemental analyses, IR, 1 H NMR, ESI-MS and single- crystal X-ray diffraction. DFT method with 6-31G(d,p) basis set was used to calculate the optimized geo- metrical parameters, vibrational frequencies and chemical shift values. The calculated vibrational fre- quencies and chemical shift values were compared with experimental IR and 1 H NMR values. The results represented that there was a good agreement between experimental and calculated values of the compounds 5a–5c. In addition, DFT calculations of the compounds, molecular electrostatic potentials (MEPs) and frontier molecular orbitals were performed at B3LYP/6-31G(d,p) level of theory. Furthermore, compounds were tested against three Gram-positive bacteria: Staphylococcus aureus ATCC 29213 (Amer- ican Type Culture Collection), methicillin resistant S. aureus (MRSA) ATCC 43300 and Enterococcus faecalis ATCC 29212; two Gram negative bacteria: Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853; and three fungi: Candida albicans ATCC 90028, Candida krusei ATCC 6258 and Candida parapsilosis ATCC 90018. In general, all of the compounds were found to be slightly active against tested microorganisms. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Nitrogen and oxygen containing heterocyclic compounds have received considerable attention due to their wide range of pharma- cological activity [1]. 2-Benzoxazolinones and their derivatives are useful intermediates in the production of pharmaceuticals, pesti- cides and herbicides [2–4]. 2-Benzoxazolinone heterocycles are considered ‘privileged scaffolds’ in the design of pharmacological probes. These heterocycles have, in fact, high versatility in chemical modifications, allowing changes to the characteristics of side-chains on a rigid platform. Moreover, they have received considerable attention from medicinal chemists, due to their capacity to mimic a phenol or a catechol moiety in a metabolically stable template 0022-2860/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.molstruc.2013.01.066 ⇑ Corresponding author. Tel.: +90 454 310 10 00. E-mail address: yelda.alpaslan@giresun.edu.tr (Y.B. Alpaslan). Journal of Molecular Structure 1039 (2013) 71–83 Contents lists available at SciVerse ScienceDirect Journal of Molecular Structure journal homepage: www.elsevier.com/locate/molstruc