1. Introduction The steadily increasing microbial resistance to existing irst drugs is a serious problem in antimicrobial cure and necessitates continuing research into new classes of antimicrobials [1]. Moreover, the progression of drug- resistant strains has contributed to the ineficiency of antimicrobial therapy. This has led to enormous interest in antibacterial research, and we strongly believe that there is an urgent call for development of new drugs with diverse and unique structures and with novel mechanisms of action from that of existing irst line drugs. Consequently, this area of research is signiicant and attracts much attention of an increasing number of medicinal chemists. Recently, we have been particularly interested in the synthesis of N-arylpyrazole and 4H-chromene incorporating structures for antimicrobial evaluation [2] on the premise that N-arylpyrazole is a chemically useful synthon bearing diverse biological activities like antimicrobial [3-5], anti-inlammatory (COX-2 inhibitor and ulcerogenic activity) [4], antitubercular [5], antitumor [6,7], antiangiogenesis [7], anti-parasitic [8], antiviral [9], analgesic and anxiolytic activity [10]. Moreover, the 4H-pyrano[3,2-c]chromene nucleus is a fertile source of biologically important molecules possessing a wide spectrum of pharmacological activities, such as antimicrobial [11], antiviral [12], mutagenicity [13], antiproliferative [14], sex pheromone [15], antitumor [16], cancer therapy [17] and central nervous system activity [18]. Despite their importance from pharmacological and synthetic point of views, comparatively few modiied methods for the preparation of 4-aryl-4H-pyrano[3,2-c] chromene derivatives [19] have been reported using piperidine, morpholine, K 2 CO 3 , diammonium hydrogen phosphate, H 6 [P 2 W 18 O 62 ]•18H 2 O, tetrabutylammonium bromide or water using various aromatic/heterocyclic aldehydes, wherein not a single reference have been found where 3-methyl-5-aryloxy-1-aryl-1H-pyrazole- 4-carbaldehyde is used. Thus, in view of the biological signiicance of 4H-chromene, a modiication of the 4-position on 4H-pyrano[3,2-c]chromene by 3-methyl- 5-phenoxy-1-phenyl-1H-pyrazole is undertaken to check whether it may bring signiicant changes in the bioactivities of 4H-chromene derivatives. As a part of our current studies in developing new antimicrobial agents via combination of two therapeutically active moieties Central European Journal of Chemistry * E-mail: patelranjanben@yahoo.com Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat, India Chetan B. Sangani, Divyesh C. Mungra, Manish P. Patel, Ranjan G. Patel * Synthesis and antimicrobial screening of pyrano[3,2-c]chromene derivatives of 1H-pyrazoles Research Article Abstract: © Versita Sp. z o.o. Received 20 January 2011; Accepted 10 March 2011 Keywords: Chromene • MCR • Pyrazole-4-carbaldehyde • Antimicrobial activity A new series of twenty four derivatives of pyrano[3,2-c]chromene IVa-x bearing 1H-pyrazole were synthesized by a one pot, base-catalyzed cyclocondensation reaction of 1H-pyrazole-4-carbaldehyde Ia-l, malononitrile II and 4-hydroxycoumarin IIIa-b. All the synthesized compounds were characterized by elemental analysis, FT-IR, 1 H NMR and 13 C NMR spectral data. All the synthesized compounds were screened against six bacterial pathogens, namely B. subtilis, C. tetani, S. pneumoniae, S. typhi, V. cholerae, E. coli and for antifungal activity against two fungal pathogens, A. fumigatus and C. albicans using the broth microdilution MIC method. Some of the compounds were found to be equipotent or more potent than commercial drugs against most of employed strains, as evident from the screening data. Cent. Eur. J. Chem. • 9(4) • 2011 • 635-647 DOI: 10.2478/s11532-011-0041-7 635