INTRODUCTION Quinazoline is an important integral part of various physio- logically and pharmaceutically important ring systems e.g. pyrazolo[5,1-b]quinazoline, pyrido[1,2-a]quinazoline and chromeno[3',4':4,5]pyrido[1,2-a] quinazoline 1 . Their derivatives show a variety of biological activities, including antihyper- tensive 2,3 antimicrobial 4,5 , antihyperlipidemic 6,7 , antiinflamma- tory 8,9 and anticonvulsant 10-14 . Quinazoline derivatives also possess diverse pharmacological activities 15,16 . A large number of quinazoline derivatives were recently synthesized in order to design more effective biologically active molecules. A three component reaction of 3-amino- pyrazole-4-carboxylic acid (I), tolualdehyde (II) and dimedone (III) on refluxing in 2-propanol gives 6,6-dimethyl-8-oxo-9- p-tolyl-4,5,6,7,8,9-hexahydropyrazolo[5,1-b]quinazoline-3- carboxylic acid (IV), which on aromatization gives a tetrahydro product ( V). A large number of medicinally important hexahydro- and tetrahydropyrazolo[5,1-b]-quinazolines bear- ing different substituents at C-3 (COOH, COOEt, CN) were synthesized in this way (Scheme-I) 17 . Structure activity relationship of a new set of related 5,6- dihydropyrazolo[4,3-h]quinazolines (Fig. 1.), having different substituents (COOEt, Cl, Br, CH3 and COOH) at position-1 was studied. These compounds were tested for their binding activity at the Gly/NMDA, AMPA and KA receptors. These studies showed that a C-1 anionic carboxylate residue on the Synthesis and Antibacterial Activity of Pyrazolo[1,5-a]quinazoline-3-carbonitriles AREESHA NAZEER 1 , NAJMA PERVEEN 2 , MISBAHUL AIN KHAN 1,2 , MUHAMMAD NAEEM KHAN 3,* , MUNAWAR ALI MUNAWAR 1 and WHEI-OH LIN 4 1 Institute of Chemistry, University of the Punjab, Quaid-e-Azam Campus, Lahore, Pakistan 2 Department of Chemistry, The Islamia Univerity of Bahawalpur, Bahawalpur, Pakistan 3 Applied Chemistry Research Center, PCSIR Laboratories Complex, Lahore, Pakistan 4 Departmento de Quimica, Universidade de Grande Rio, Rua Jose Herdy, Duque de Caxias, RJ, Brazil *Corresponding author: E-mail: changwani_1@yahoo.com (Received: 14 September 2012; Accepted: 8 July 2013) AJC-13790 A method for the synthesis of 4,5,6,7, 8,9- hexahydro-5-arylpyrazolo[1,5-a]quinazoline-3-carbonitriles was developed. 5-Aminopyrazole- 4-carbonitrile when reacted with aromatic aldehydes gives the schiff's base which on cyclization with cyclohexanone in the presence of glacial acetic acid produces a series of title compounds. The synthesized compounds were characterized through elemental analysis and spectroscopic techniques (FTIR, 1 H NMR and MS). The antibacterial activity of these compounds was also tested against six different bacterial strains by agar plate disc method. Key Words: Pyrazoloquinazolines, Pyrazoles, Schiff's bases, Cyclizations. pyrazolo[1,5-c]quinazoline-2-carboxylate core enhances the receptor binding activity. Among the pyrazoloquinazoline series of compounds, 1,2-dicarboxylic acid derivative showed the highest receptor binding activity 18 . N N H NH2 O HO + CH3 O O O + N N N O HO O CH3 H (I) (II) (III) (IV) (V) 2-P ropanol N N N O HO O CH3 Scheme-I A three component condensation reaction of amino- pyrazoles, diones and arylaldehydes resulted in the formation Asian Journal of Chemistry; Vol. 25, No. 14 (2013), 7705-7709 http://dx.doi.org/10.14233/ajchem.2013.14573