Scholarly article on topic 'Classical and microwave assisted synthesis of new 4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives and their antimicrobial activities'

Classical and microwave assisted synthesis of new 4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives and their antimicrobial activities Academic research paper on "Chemical sciences"

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{Quinazolinone / Hydrazono / Pyrazole / Microwave / Antimicrobial}

Abstract of research paper on Chemical sciences, author of scientific article — Natvar A. Sojitra, Ritu B. Dixit, Rajesh K. Patel, Jayanti P. Patel, Bharat C. Dixit

Abstract A simple and efficient methodology was developed for the synthesis of new 4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives 10a–10j in good amount of yields. They have been prepared using 2-acetamidobenzoic acid derivatives 2a–2j via intermediates benzenesulfonamide substituted quinazolinone derivatives 8a–8j, and its corresponding hydrazono derivatives 9a–9j. Entitled compounds (10a–10j) were also obtained using microwave heating in good amount of yields. The structures of all the new compounds have been evaluated on the basis of elemental analysis, FT-IR, 1H and 13C NMR spectral studies. Entitle compounds have been screened for their in vitro antimicrobial activities and all these compounds displayed excellent to moderate activities, which were found to be significantly potent against bacteria compared to fungal.

Academic research paper on topic "Classical and microwave assisted synthesis of new 4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives and their antimicrobial activities"

Journal of Saudi Chemical Society (2012) xxx, xxx-xxx

ORIGINAL ARTICLE

Classical and microwave assisted synthesis of new 4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives and their antimicrobial activities

Natvar A. Sojitra a, Ritu B. Dixit b, Rajesh K. Patel c, Jayanti P. Patel a, Bharat C. Dixit a *

a Chemistry Department, V.P. & R.P.T.P. Science College, Affiliated to Sardar Patel University, Vallabh Vidyangar 388 120, Gujarat, India

b Ashok and Rita Patel Institute of Integrated Study and Research in Biotechnology and Allied Sciences, New Vallabh Vidyangar 388 121, Gujarat, India

c Department of Life Sciences, Hemchandracharya North Gujarat University, Patan 384 265, Gujarat, India Received 26 April 2012; accepted 10 July 2012

KEYWORDS

Quinazolinone;

Hydrazono;

Pyrazole;

Microwave;

Antimicrobial

Abstract A simple and efficient methodology was developed for the synthesis of new 4-(3, 5-dimethyl-1 -phenyl-1 H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesul-fonamide derivatives 10a-10j in good amount of yields. They have been prepared using 2-acetam-idobenzoic acid derivatives 2a-2j via intermediates benzenesulfonamide substituted quinazolinone derivatives 8a-8j, and its corresponding hydrazono derivatives 9a-9j. Entitled compounds (10a-10j) were also obtained using microwave heating in good amount of yields. The structures of all the new compounds have been evaluated on the basis of elemental analysis, FT-IR, 1H and 13C NMR spectral studies. Entitle compounds have been screened for their in vitro antimicrobial activities and all these compounds displayed excellent to moderate activities, which were found to be significantly potent against bacteria compared to fungal.

© 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.

1. Introduction

* Corresponding author. Tel.: +91 2692230599. E-mail address: dixits20002003@yahoo.co.in (B.C. Dixit). Peer review under responsibility of King Saud University.

Perusal of literature survey reveals that the quinazolinone skeleton is found in a number of biologically active molecules. There are various reports regarding substitution at 2nd and/ or 3rd position of quinazolinone skeleton. Specifically, 4(3H)-quinazolinone derivatives display a broad range of biological properties such as antihypertensive (Haruhisa et al., 2006), CNS depressant (Kashaw et al., 2009; Saber et al.,

1319-6103 © 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/jjscs.2012.07.020

2007), antitumor, analgesic and anti-inflammatory, antibacterial and antifungal activities (Pandey et al., 2009; Laddha et al., 2006; Sondhi et al., 2010). Octahydroquinazolinone derivatives have exhibited potent antibacterial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa (Kidwai et al., 2005) and calcium antagonist activity (Yarim et al., 2002, 2003; Kantevari et al., 2006). These classes of compounds have also shown interference with insulin secretion and smooth muscle contractile channel activity (Somers et al., 2001). On the other hand, various therapeutic activities have also been reported for the pyrazole moieties (Hong et al., 2009; Badawey and El-Ashmawey, 1998; Bailey et al., 1985). However, there are no such reports in which both quinazoli-none and pyrazole rings are linked by benzenesulfonamide substituted hydrazono bridge. Therefore, it was thought interesting to bring the above two moieties within a single molecular framework to afford their additive biological properties. Thus, the present communication comprises synthesis, characterization and antimicrobial activities of newer 4-(3,5-dimethyl -1-phenyl-1H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives 10a-10j.

2. Results and discussion

2.1. Chemistry

Majority of the reported 4(3H)-quinazolinone derivatives were synthesized either from anthranilic acid or its derivatives (Hisano, 1973) (shown in Scheme 1). There are very few reports (Zahran, 2000; Gupta et al., 1988; Morsy, 2007) regarding preparation of the compound 6a, expect our recently reported work [8a-8j] (Jagani et al., 2011). The reported methods for the synthesis of compound 6a involve the sulfonylation of 3-aminoquinazolinone (4) using p-acetamidobenzenesulfo-nylchloride (5) under reflux condition in the presence of base (i.e. pyridine or NaOH) as shown in Scheme 1 (yields were in the range of 58 to 66%). In another report (Yuefen et al., 2004), compound 6a was prepared using 2-methyl-4H-3,1-benzoxazin-4-one (3) and N-[4-(hydrazinosulfonyl)phenyl] acetamide (7) as shown in Scheme 1.

The above methods proceed via highly moisture sensitive, irritant, and electronically unsaturated character of unstable 2-methyl-4H-3,1-benzoxazin-4-one (3) bearing substitution at second position which renders them difficult to synthesize (Madkour, 2005). In addition to this, more number of synthetic steps decreases the overall yield.

To overcome such problems, we have established the reaction pathway for the synthesis of 4-amino-N-(2-methyl-4-oxo-quinazolin-3(4H)-yl)benzenesulfonamide 8a and its derivatives (8a-8j) (Jagani et al., 2011), which was again optimized by changing reaction conditions to prepare the same compounds and is shown in Scheme 2. The structure of compounds 8a-8j was confirmed by mass spectra and melting point.

4-[N'-(1-Acetyl-2-oxo-propylidene)hydrazino]-N-(2-methyl-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives 9a-9jwere prepared starting from 4-amino-N-(2-methyl-4-oxoqui-nazolin-3(4H)-yl)benzenesulfonamide 8a-8j, and is shown in Scheme 3.

Pyrazole derivatives (10a-10j) were prepared via both classical and microwave irradiation from hydrazono compounds (9a-9j), as shown in Scheme 3. Comparisons of both synthetic approaches have been displayed in Table 1, which showed optimization of reaction time and an increase in yields under microwave condition.

The structure of compounds 9a-9jwas confirmed by IR, *H NMR, 13C NMR, and mass spectra and the characterization of 9a is included herewith (Pavia et al., 2008). The IR spectrum of 9a showed the presence of C=O group at 1695 cm-1 due to CONH and COCH3 groups. Two sharp bands at 1324 and 1142 cm-1 were due to asymmetric and symmetric stretching vibrations of SO2 group, respectively. The two bands at 1510 and 1550 cm-1 were due to N—H bending of secondary amine and sulfonamide groups respectively. The *H NMR of 9a showed a singlet at d 10.91 ppm due to highly deshielded proton of NHSO2 group. One singlet was observed at d 9.11 ppm due to secondary amine group. The two more singlets appeared in the aliphatic region at d 2.51 and 2.25 ppm due to COCH3 and CH3 protons at second position of the quinaz-olinone ring respectively. All the 8 aromatic protons resonated in the region of d 7.75-6.63 ppm. The 13C NMR of 9a showed two signals of carbonyls carbon at d 190.0 ppm (COCH3) and

Scheme 2 Proposed synthetic route for the synthesis of p-aminobenzenesulfonamide substituted quinazolin-4(3H)-one 8a-8j.

] Oa-1 Oj

Scheme 3 Proposed synthetic route for hydrazono 9a-9j and pyrazole 10a-10j derivatives of quinazolin-4(3H)-one.

Table 1 Comparison of time consumed and yield obtained under conventional and microwave heating.

S. No. Substitution Conventional heating Microwave heating

R Ri R2 Time (h) Yield (%) Time (min.) Yield (%) Power (watt)

10a CH3 H H 6.5 73 5.0 78 210

10b CH3 Br H 7.0 76 5.5 82 210

10c CH3 Br Br 7.5 83 6.0 88 245

10d C6H5 no2 H 6.0 78 5.0 79 245

10e C6H5 H H 5.5 81 4.5 84 210

10f C6H5 Br H 6.0 71 5.0 77 210

10g C6H5 Br Br 7.5 78 6.0 83 245

10h 4-Cl—C6H4 H H 7.0 73 6.5 76 245

10i 4-Cl—C6H4 Br H 6.5 78 5.5 86 245

10j 4-Cl—C6H4 Br Br 6.5 73 6.0 84 245

188.1 ppm (CO of quinazolinone). The aromatic carbons appeared at d 158.6, 153.1, 146.5, 135.4, 130.2, 127.5, 127.1, 126.8, 123.7, 121.0, and 113.0 ppm. Signals due to remaining two quaternary carbons appeared at d 157.3 ppm (N=C-CH3) and 130.25 ppm (CO-C-CO). The signals due to aliphatic carbons appeared at 28.8 ppm (COCH3) and 23.1 ppm (CH3). The molecular ion peak (m/z) was observed at 442.2 in the mass spectrum of 9a for molecular formula C20H19N5O5S. Similarly, the data for compounds 9a-9jare given in the experimental section.

4-(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-sub stituted-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide derivatives 10a-10jwere prepared from 4-[N-(1-acetyl-2-oxo-propyl-idene)hydrazino]-N-(2-methyl-4-oxo-4H-quinazolin-3-yl) benzenesulfonamide derivatives 9a-9jby cyclization in the presence of phenyl hydrazine and is shown in Scheme 3. The structures of compounds 10a-10jwere confirmed by IR, *H NMR, 13C NMR, and mass spectra and are described in the experimental section. The data of compound 10a were com-

pared with the data of compound 9a. The IR spectrum of 10a showed the band at 1698 cm-1 due to the presence of C=O group of quinazolinone ring (Pavia et al., 2008; Mikhailovskii and Shklyaev, 1992), the band at 1510 cm-1 due to N-H bending of secondary amine in compound 9a disappeared in compound 10a due to cyclization and a new band appeared at 1580 cm-1 due to N=N stretching. The bands due to NHSO2 and C=O groups were not much affected. In contrast to the 1H NMR spectrum of compound 9a, in the 1H NMR spectrum of compound 10a, the NH proton singlet at d 9.11 ppm and the COCH3 protons at d 2.51 ppm of 9a disappeared due to the formation of pyrazole ring. The 13C NMR of 10a showed the signal of carbonyl carbon at d 158.3 ppm due to CO group of quinazolinone ring. The aromatic carbons appeared at d 151.9, 146.8, 146.1, 144.0, 139.1, 135.4, 128.6, 127.1, 126.8, 126.0, 123.7, 121.0, 119.6, and 113.0 ppm. Signals due to remaining two quaternary carbons appeared at d 156.5 ppm for N=C-CH3 in quinazolinone ring and 130.2 ppm for carbon of pyrazole ring (C-C-CH3). In the

Table 2 Antimicrobial activity of the synthesized compounds.

Compound Minimum Inhibitory Concentration ig/mL

Gram positive bacteria Gram negative bacteria Fungal

S. aureus B. subtilis E. coli P. aeruginosa A. niger A. clavatus

9a 25 200 50 150 200 250

9b 100 200 200 200 200 250

9c 200 100 150 250 250 250

9d 50 100 200 50 250 200

9e 250 150 250 250 >200 250

9f 100 200 100 200 200 250

9g 150 250 250 25 >200 250

9h 200 25 200 200 200 200

9i 150 200 25 50 200 250

9j 200 200 200 150 200 250

10a 25 250 200 100 200 250

10b <100 50 200 200 200 250

10c 150 25 200 250 >200 250

10d 200 100 150 200 250 250

10e 250 250 100 100 250 >200

10f 100 200 200 150 250 200

10g 25 200 250 250 >200 250

10h 50 150 150 200 200 250

10i 100 200 >250 150 >200 250

10j 150 >250 100 100 250 250

Streptomycin 10 10 10 10 - -

Nystatin - - - - 50 50

downfield region the signal appeared at 22.5 ppm due to the methyl groups at second position of the quinazolinone ring and two signals at 12.2 and 10.3 ppm due to pyrazole ring. The molecular ion peak (m/z) appeared at 514.2 in the mass spectrum of 10a for molecular formula C26H23N7O3S.

2.2. Evaluation of in vitro antimicrobial activity

The in vitro antimicrobial activities of the synthesized compounds 9a-9jand 10a-10jhave been investigated against the bacterial species S. aureus (ATCC 25923), Bacillus subtilis (ATCC 11774), E. coli (ATCC 25922) and P. aeruginosa (ATCC 25619), whereas of fungal species Aspergillus niger (ATCC 64958) and Aspergillus clavatus (ATCC 66027). The antibacterial and antifungal activities have been performed using the serial broth dilution method (Jani et al., 2010; Thangadurai and Natarajan, 2001). The minimum inhibitory concentration (MIC) values of the compounds are summarized in Table 2.

The antibacterial evaluation of the synthesized compounds revealed that among all the compounds 9a, 9d, 10a, 10c, 10g and 10h showed excellent activity against Gram positive B. subtilis, whereas compounds 9h, 10b and 10c showed good activity against S. aureus. Similarly compounds 9a and 9i showed excellent results against Gram negative bacterial species E. coli, while compounds 9d, 9g and 9i showed good activity against P. aeruginosa. Compound 10e was poor against B. subtilis. While remaining compounds were moderately or slightly active against Gram-positive and Gram-negative bacteria species. In vitro antimicrobial activities and all these compounds displayed excellent to moderate activity, which were found to be significantly potent against bacteria as compared to fungal.

3. Experimental

3.1. Material and measurements

All reagents were of analytical reagent (AR) grade purchased commercially from Spectro chem. Ltd., Mumbai, India and used without further purification. Solvents employed were distilled, purified and dried by standard procedures prior to use (Jeffery, 1989). All reactions were monitored by thin-layer chromatography (TLC on aluminum plates coated with silica gel 60 F254, 0.25 mm thickness, E. Merck, Mumbai, India) and detection of the components were measured under UV light or explored in Iodine chamber. Carbon, hydrogen and nitrogen elemental analyses were estimated by a PerkinElmer 2400-II CHN elemental analyzer, USA. *H and 13C NMR measurements were carried out on a Bruker Advance-II 400 MHz NMR spectrometer. The chemical shifts were measured with respect to TMS which was used as an internal standard and DMSO-d6 used as solvent. Infrared spectra of compounds were recorded in the region of 4000400 cm-1 on a Shimadzu 8501 Fourier-Transform Infrared Spectrophotometer using KBr pellets. Mass spectra were scanned on a Shimadzu LCMS 2010 spectrometer. Melting point of the compounds was measured by the open capillary tube method.

3.2. General procedure for the preparation of 3-sulfonamide substituted quinazolinone derivatives 8a-8j

In a three-necked, 500 mL, round bottom flask equipped with a mechanical stirrer, reflux condenser, pressure equalizer funnel were placed N-[5-(hydrazinosulfonyl)phenyl]acetamide 7

(0.1 mol) and 2-acetamidobenzoic acid derivatives 2a-2j (0.1 mol) which were prepared by the reported method (Friedman et al., 1960; Jeffery et al., 1989) and 175 mL of toluene. The mixture was stirred well and treated drop-wise with a solution of phosphorus trichloride (0.0335 mol) in 25 mL of toluene over a period of 15 min. The resulting suspension was refluxed in oil-bath at 130 0C for 2-3 h. The progress of reaction was monitored by TLC (9:1, CHCl3:CH3OH solvent system). The solvent was removed by vacuum distillation and the residue thus obtained was treated with 200 mL of 10% sodium carbonate solution. Thus, the solid product obtained was filtered, washed with distilled water and dried at 60 0C. The white product was obtained after recrystallization using 75 mL of 95% ethanol solution. The product was then taken in 500 mL round bottom flask containing 200 mL of 50% HCl solution. The mixture was then refluxed until the clear solution was obtained. The resulting solution was cooled and basified with 10% NaOH solution. The precipitated product was filtered and washed with distilled water. It was recrys-tallized using 75 mL of 95% ethanol.

3.3. General procedure for the diazotization of sulfonamide substituted 4-(3H)-quinazolinone derivatives

Diazotization of compounds 8a-8jwas carried out by the reported method (Jeffery et al., 1989). Accordingly, a solution of compounds 8a-8j(0.01 mol) in 3 mL concentrated HCl was cooled to 0-5 0C in ice bath. The cooled sodium nitrite solution (1.5 g. in 10 mL of water) was added to it dropwise for 10 min. The reaction mixture was then stirred for 30 min. to produce diazotized compounds (Scheme 3). The reaction mass was stored at 0-5 0C and was directly used for the next step.

3.4. General procedure for the preparation of hydrazono derivatives 9a-9j

Compounds 9a-9j were prepared using an ice-cold mixture of the active methylene compound (acetyl acetone) (0.01 mol) and sodium acetate (0.05 mol) in ethanol (50 mL) was added dropwise with stirring to a solution of diazotized compounds 8a-8j over a period of 15 min. The stirring was continued for 30 min. and the reaction mixture was then left for 2 h. at room temperature, and the progress of reaction was monitored by TLC (9:0.5, CHCl3:MeOH solvent system). The solid yellow product thus obtained was filtered, washed with cold water and recrystallized from ethanol to give the corresponding hydrazono derivatives 9a-9j.

3.4.1. 4-[N-(1-Acetyl-2-oxo-propylidene)hydrazino]-N-(2-methyl-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide (9a) Yellow crystals (61%), m.p. 167-168 oc, Anal. Calcd. For C20H19N5O5S: C, 54.41; H, 4.34; N, 15.86%. Found: C, 54.55; H, 4.42; N, 15. 69%. IR (KBr, cm-1): 3056 (aromatic C—H stretching), 2863 (aliphatic C—H stretching), 1695 (C=O stretching), 1601 (aromatic C=C stretching), 1510 (aromatic N—H bending), 1550 (N—H bending of SO2NH group), 1450 (aliphatic C—H bending), 1324, 1142 (asymmetric and symmetric S=O stretching). *H NMR (400 MHz, DMSO-d6): d 10.91 (s, 1H), 9.11 (s, 1H), 7.75 (dd, J = 7.91, 1.46 Hz, 1H), 7.69 (td, J = 12.06, 1.48 Hz, 1H), 7.55 (dd,

J = 7.96, 1.40 Hz, 1H), 7.36 (td, J =7.16, 1.40 Hz, 1H), 7.11 (dd, J= 8.67, 2.61 Hz, 2H), 6.53 (dd, J= 9.71, 2.15 Hz, 2H), 2.51 (s, 6H), 2.25 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 190.0, 188.1, 158.6, 157.3, 153.1, 146.5, 135.4, 130.2, 127.1, 126.8, 123.7, 121.0, 113.0, 28.8, 23.1. MS (ESI) (m/z): 442.2 [M + H] + .

3.4.2. 4-[N-(1-Acetyl-2-oxo-propylidene)hydrazino]-N-(6-bromo-2-methyl-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide (9b)

Yellow crystals (62%), m.p. 145-147 oc, Anal. Calcd. For C20H18BrN5O5S: C, 46.16; H, 3.49; N, 13.46%. Found: C, 46.34; H, 3.58; N, 13.60%. IR (KBr, cm-1): 3073 (aromatic C—H stretching), 2864 (aliphatic C—H stretching), 1697 (C=O stretching), 1601 (aromatic C=C stretching), 1512 (aromatic N—H bending), 1556 (N—H bending of SO2NH group), 1451 (aliphatic C—H bending), 1322, 1139 (asymmetric and symmetric S=O stretching). *H NMR (400 MHz, DMSO-d6): d 10.79 (s, 1H), 9.21 (s, 1H), 8.42 (d, J = 2.21 Hz, 1H), 7.70 (d, J = 10.45 Hz, 1H), 7.59 (dd, J = 10.49, 2.17 Hz, 1H), 7.35 (dd, J = 8.64, 2.62 Hz, 2H),

6.46 (dd, J = 8.72, 2.13 Hz, 2H), 2.49 (s, 6H), 2.31 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 192.5, 191.1, 162.2, 158.1, 152.6, 147.9, 137.2, 131.3, 125.3, 124.2, 126.6, 126.1, 123.8, 121.9, 113.1, 27.9, 25.8, 24.1. MS (ESI) (m/z): 520.1, 522.3 [M] + .

3.4.3. 4-[N -(1-Acetyl-2-oxo-propylidene)hydrazino]-N-(6,8-dibromo-2-methyl-4-oxo-4H-quinazolin-3-yl)-benzenesulfonamide (9c)

Yellow crystals (65%), m.p. 172-174 oc, Anal. Calcd. For C20H17Br2N5O5S: C, 40.09; H, 2.86; N, 11.69%. Found: C 40.18, H 2.98, N 11.80%. IR (KBr, cm-1): 3062 (aromatic C—H stretching), 2855 (aliphatic C—H stretching), 1696 (C=O stretching), 1602 (aromatic C=C stretching), 1511 (aromatic N—H bending), 1553 (N—H bending of SO2NH group), 1453 (aliphatic C—H bending), 1323, 1141 (asymmetric and symmetric S=O stretching). *H NMR (400 MHz, DMSO-d6): d 10.82 (s, 1H), 9.21 (s, 1H), 8.47 (d, J = 2.38 Hz, 1H), 8.08 (d, J = 2.35 Hz, 1H), 7.40 (dd, J = 8.67, 2.61 Hz, 2H), 6.57 (dd, J = 10.72, 2.54 Hz, 2H), 2.48 (s, 6H), 2.28 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 191.6, 184.1, 166.2, 162.3, 151.7, 151.6, 137.9, 132.6, 130.3,

129.1, 126.2, 124.4, 118.4, 114.1, 114.1, 26.8. MS (ESI) (m/z):

597.2, 599.1, 601.3 [M] + .

3.4.4. 4-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-N-(6-nitro-4-oxo-2-phenylquinazolin-3(4H)-yl)benzenesulfonamide (9d)

Yellow crystals (61%), m.p. 189-190 oc, Anal. Calcd. For C25H20N6O7S: C, 54.74; H, 3.68; N, 15.32%. Found: C, 54.49; H, 3.76; N, 15.22%. IR (KBr, cm-1): 3058 (aromatic C—H stretching), 2858 (aliphatic C—H stretching), 1694 (C=O stretching), 1602 (aromatic C=C stretching), 1510 (aromatic N—H bending), 1552 (N—H bending of SO2NH group), 1456 (aliphatic C—H bending), 1321, 1143 (asymmetric and symmetric S=O stretching). *H NMR (400 MHz, DMSO-d6): d 10.88 (s, 1H), 9.14 (s, 1H), 6.9-8.6 (m, 12H),

2.47 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 198.3, 161.4, 153.7, 152.2, 146.6, 132.0, 131.4, 130.2, 130.1, 129.1, 128.7, 128.3, 128.1, 125.5, 123.6, 123.0, 121.9, 116.8, 26.9. MS (ESI) (m/z): 549.4 [M + H] + .

3.4.5. 4-[N'-(1-Acetyl-2-oxopropylidene)hydrazino]-N-(4-oxo-2-phenyl-4H-quinazolin-3-yl)benzenesulfonamide (9e)

Yellow crystals (64%), m.p. 164-166 0C, Anal. Calcd. For C25H21N5O5S: C, 59.63; H, 4.20; N, 13.91%. Found: C, 59.54; H, 4.40; N, 13.99%. IR (KBr, cm-1): 3071 (aromatic C—H stretching), 2891 (aliphatic C—H stretching), 1698 (C=O stretching), 1608 (aromatic C=C stretching), 1501 (aromatic N—H bending), 1560 (N—H bending of SO2NH group), 1462 (aliphatic C—H bending), 1326, 1135 (asymmetric and symmetric S=O stretching). NMR (400 MHz, DMSO-d6): d 10.88 (s, 1H), 9.20 (s, 1H), 6.5-8.2 (m, 13H), 2.53 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 195.6, 191.1, 161.9, 153.6, 151.5, 147.5, 136.2, 132.8, 133.6, 132.5, 128.7, 126.9, 126.8, 126.1, 125.0, 124.8, 123.6, 121.6, 114.3,

27.7, 25.9. MS (ESI) (m/z): 504.2 [M + H] + .

3.4.6. 4-[N'-(1-Acetyl-2-oxopropylidene)hydrazino]-N-(6-bromo-4-oxo-2-phenyl-4H-quinazolin-3-yl)benzenesulfonamide

Yellow crystals (65%), m.p. 183-184 0C, Anal. Calcd. For C25H20BrN5O5S: C, 51.55; H, 3.46; N, 12.02%. Found: C, 51.64; H, 3.53; N, 12.07%. IR (KBr, cm-1): 3068 (aromatic C—H stretching), 2882 (aliphatic C—H stretching), 1694 (C=O stretching), 1602 (aromatic C=C stretching), 1498 (aromatic N—H bending), 1550 (N—H bending of SO2NH group), 1450 (aliphatic C—H bending), 1321, 1136 (asymmetric and symmetric S=O stretching). NMR (400 MHz, DMSO-d6): d 10.91 (s, 1H), 9.10 (s, 1H), 6.5-8.4 (m, 12H), 2.49 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 198.6, 194.1, 165.4, 153.6, 152.6, 147.6, 138.6, 132.9, 131.7, 130.8,

130.0, 129.6, 127.1, 126.3, 126.0, 124.6, 122.7, 115.8, 115.1,

28.8, 26.0. MS (ESI) (m/z): 582.3, 584.4 [M]+.

3.4.7. 4-[N'-(1-Acetyl-2-oxo-propylidene)hydrazino]-N-(6,8-dibromo-4-oxo-2-phenyl-4H-quinazolin-3-yl)benzenesulfonamide (9g)

Yellow crystals (61%), m.p. 193-195 oc, Anal. Calcd. For C25H19Br2N5O5S: C, 45.40; H, 2.90; N, 10.59%. Found: C, 45.45; H, 2.99; N, 10.68%. IR (KBr, cm-1): 3067 (aromatic C—H stretching), 2858 (aliphatic C—H stretching), 1694 (C=O stretching), 1601 (aromatic C=C stretching), 1503 (aromatic N—H bending), 1551 (N—H bending of SO2NH group), 1452 (aliphatic C—H bending), 1326, 1141 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.86 (s, 1H), 9.13 (s, 1H), 6.6-8.5 (m, 11H), 2.53 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 178.6,

174.1, 163.9, 159.6, 153.1, 152.8, 138.4, 134.7, 133.7, 131.5, 129.9, 129.7, 127.3, 126.0, 125.1, 124.4, 119.0, 114.1, 111.0,

27.9, 25.9. MS (ESI) (m/z): 660.0, 662.2, 663.9 [M]+.

3.4.8. 4-[N'-(1-Acetyl-2-oxopropylidene)hydrazino]-N-[2- (4-chlorophenyl)-4-oxo-4H-quinazolin-3-yl]benzenesulfonamide (9h)

Yellow crystals (65%), m.p. 178-180 oc, Anal. Calcd. For C25H20ClN5O5S: C, 55.81; H, 3.75; N, 13.02%. Found: C, 55.83; H, 3.83; N, 13.11%. IR (KBr, cm-1): 3077 (aromatic C—H stretching), 2861 (aliphatic C—H stretching), 1693 (C=O stretching), 1602 (aromatic C=C stretching), 15012 (aromatic N—H bending), 1555 (N—H bending of SO2NH group), 1446 (aliphatic C—H bending), 1325, 1145 (asymmet-

ric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.84 (s, 1H), 9.09 (s, 1H), 6.6-8.1 (m, 12H), 2.49 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 197.3, 187.3, 165.9, 154.8, 148.4, 135.9, 134.2, 132.9, 130.2, 129.4, 128.1, 127.8, 127.5, 126.0, 125.4, 124.6, 123.8, 113.2, 28.8, 25.1. MS (ESI) (m/z): 538.0, 539.8 [M] + .

3.4.9. 4-[N'-(1-Acetyl-2-oxopropylidene)hydrazino]-N-[6-bromo-2-(4-chlorophenyl)-4-oxo-4H-quinazolin-3-yl]benzenesulfonamide (9i)

Yellow crystals (64%), m.p. 203-204 oc, Anal. Calcd. For C25H19BrClN5O5S: C, 48.68; H, 3.10; N, 11.35%. Found: C 48.56, H 3.04, N 11.27%. IR (KBr, cm-1): 3069 (aromatic C—H stretching), 2873 (aliphatic C—H stretching), 1698 (C=O stretching), 1600 (aromatic C=C stretching), 1504 (aromatic N—H bending), 1551 (N—H bending of SO2NH group), 1449 (aliphatic C—H bending), 1322, 1140 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.81 (s, 1H), 9.16 (s, 1H), 6.6-8.2 (m, 11H), 2.49 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 193.4, 191.6, 158.4, 153.7, 152.5, 149.3, 138.6, 137.9, 133.6, 133.0,

131.0, 129.8, 129.5, 128.2, 126.2, 125.8, 124.6, 123.1, 115.7,

113.1, 29.8, 25.7. MS (ESI) (m/z): 616.2, 617.9, 620.0 [M] + .

3.4.10. 4-[N'-(1-Acetyl-2-oxopropylidene)hydrazino]-N-[6,8-dibromo-2-(4-chlorophenyl)-4-oxo-4H-quinazolin-3-yl]benzenesulfonamide (9j)

Yellow crystals (65%), m.p. 214-215 oc, Anal. Calcd. For C25H18Br2ClN5O5S: C, 43.16; H, 2.61; N, 10.07%. Found: C, 43.02; H, 2.50; N, 10.01%. IR (KBr, cm-1): 3052 (aromatic C—H stretching), 2868 (aliphatic C—H stretching), 1692 (C=O stretching), 1601 (aromatic C=C stretching), 1509 (aromatic N—H bending), 1556 (N—H bending of SO2NH group), 1453 (aliphatic C—H bending), 1328, 1142 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.83 (s, 1H), 9.17 (s, 1H), 8.46 (d, J =2.38 Hz, 1H), 8.11 (d, J =2.38 Hz, 1H), 7.92 (dd, J = 8.23, 2.77 Hz, 2H), 7.48 (dd, J = 8.21, 2.70 Hz, 2H), 7.35 (dd, J = 8.26, 2.81 Hz, 2H), 6.54 (dd, J = 10.12, 2.63 Hz, 2H), 2.46 (s, 6H). 13C NMR (100 MHz, DMSO-d6): d 191.4, 177.5, 162.9, 161.4, 153.3, 152.8, 138.3, 137.6, 134.6, 133.3, 131.9, 130.4, 130.7, 126.1, 125.9, 123.8, 123.7, 118.5, 115.1, 112.0, 32.8, 24.7. MS (ESI) (m/z): 693.8, 695.7, 697.7, 699.9 [M]+.

3.5. General cyclization procedure for the preparation of pyrazole substituted quinazolinone derivatives 10a-10j

It was prepared using the solution of the appropriate hydazon-o compounds 9a-9j(0.01 mol) in 30 ml of glacial acetic acid added with phenyl hydrazine (0.012 mol) and anhydrous sodium acetate (0.01 mol). The reaction mixture was heated under reflux subsequently for 4-8 h. After completion of reaction (checked by TLC using 9:0.5, CHCl3:CH3OH solvent system), the mixture was poured into ice-cold water and stored in a refrigerator until the product separated out. The crude product, was filtered, washed with water, dried and recrystallized from methanol. The colors of the compounds were yellowish orange to orange and are soluble in polar organic solvents like methanol, ethanol and pyridine.

3.5.1. 4-(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(2-methyl-4-oxo-4H-quinazolin-3-yl)benzenesulfonamide (10a)

Orange crystals (73%), m.p. 189-190 oc, Anal. Calcd. For C26H23N7O3S: C, 60.81; H, 4.51; N, 19.09%. Found: C, 60.93; H, 4.65; N, 19.22%. IR (KBr, cm-1): 3050 (aromatic C—H stretching), 2862 (aliphatic C—H stretching), 1697 (C=O stretching), 1601 (aromatic C=C stretching), 1580 (N=N stretching), 1554 (N—H bending of SO2NH group), 1453 (aliphatic C—H bending), 1324, 1142 (asymmetric and symmetric S=O stretching). NMR (400 MHz, DMSO-d6): d 10.80 (s, 1H), 6.8-7.9 (m, 13H) 2.87 (s, 3H), 2.44 (s, 3H), 2.30 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 158.3,

156.5, 153.2, 151.9, 146.8, 146.1, 144.0, 139.1, 135.4, 130.2,

128.6, 127.1, 126.8, 126.0, 123.7, 121.0, 119.6, 113.0, 22.5, 12.2, 10.3. MS (ESI) (m/z): 514.2 [M + H] + .

3.5.2. N-(6-Bromo-2-methyl-4-oxo-4H-quinazolin-3-yl)-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10b) Orange crystals (76%), m.p. 195-196 oc, Anal. Calcd. For C26H22BrN7O3S: C, 52.71; H, 3.74; N, 16.55%. Found: C, 52.89; H, 3.86; N, 16.72%. IR (KBr, cm-1): 3068 (aromatic C—H stretching), 2857 (aliphatic C—H stretching), 1693 (C=O stretching), 1602 (aromatic C=C stretching), 1573 (N=N stretching), 1550 (N—H bending of SO2NH group), 1455 (aliphatic C—H bending), 1322, 1140 (asymmetric and symmetric S=O stretching). *H NMR (400 MHz, DMSO-d6): d 10.83 (s, 1H), 6.8-8.3 (m, 12H) 2.77(s, 3H), 2.57 (s, 3H), 2.37 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 162.3, 158.5, 152.2, 150.4, 148.7, 147.6, 142.9, 138.3, 136.1, 133.2, 128.4, 127.6, 127.3, 127.2, 126.7, 125.2, 122.3, 117.5, 116.2, 24.0, 13.1, 10.1. MS (ESI) (m/z): 592.2, 594.1 [M] + .

3.5.3. N-(6,8-Dibromo-2-methyl-4-oxo-4H-quinazolin-3-yl)-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10c)

Orange crystals (83%), m.p. 174-176 oc, Anal. Calcd. For C26H21Br2N7O3S: C, 46.51; H, 3.15; N, 14.60%. Found: C, 46.63; H, 3.24; N, 14.74%. IR (KBr, cm-1): 3061 (aromatic C—H stretching), 2876 (aliphatic C—H stretching), 1694 (C=O stretching), 1601 (aromatic C=C stretching), 1576 (N=N stretching), 1553 (N—H bending of SO2NH group), 1460 (aliphatic C—H bending), 1319, 1138 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.77 (s, 1H), 7.1-8.5 (m, 11H) 2.83 (s, 3H), 2.51 (s, 3H), 2.35 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 165.1,

163.4. 153.2, 152.4, 151.3, 145.5, 145.0, 141.2, 139.6, 133.6, 131.2, 129.6, 127.0, 125.8, 123.2, 121.3, 117.3, 113.4, 24.1, 11.7, 11.1. MS (ESI) (m/z): 670.2, 672.3, 674.2 [M] + .

3.5.4. 4-((3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)diazenyl)-N-(6-nitro-4-oxo-2-phenylquinazolin-3(4H)-yl)benzenesulfonamide (10d)

Yellowish-orange crystals (78%), m.p. 224-225 oC, Anal. Calcd. For C31H24N8O5S: C, 59.99; H, 3.90; N, 18.05%. Found: C, 60.12; H, 3.74; N, 17.97%. IR (KBr, cm-1): 3064 (aromatic C—H stretching), 2852 (aliphatic C—H stretching), 1697 (C=O stretching), 1603 (aromatic C=C stretching), 1578 (N=N stretching), 1550 (N—H bending of SO2NH group), 1450 (aliphatic C—H bending), 1324, 1144 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.91 (s, 1H), 7.2-8.7 (m, 17H) 2.47 (s, 3H), 2.32 (s, 3H). 13C

NMR (100 MHz, DMSO-d6): d 162.5, 158.7, 155.5, 151.8,

145.2, 140.1, 139.4, 137.9, 132.3, 130.8, 129.7, 129.2, 128.7,

128.3, 128.0, 127.3, 126.7, 125.9, 125.5, 124.9, 124.5, 122.3, 110.5, 19.2, 11.7. MS (ESI) (m/z): 620.9 [M + H] + .

3.5.5. 4-(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-ylazo)-N-(4-oxo-2-phenyl-4H-quinazolin-3-yl)benzenesulfonamide (10e) Orange crystals (81%), m.p. 241-243 0C, Anal. Calcd. For C31H25N7O3S: C, 64.68; H, 4.38; N, 17.03%. Found: C, 64.86; H, 4.54; N, 17.18%. IR (KBr, cm-1): 3077 (aromatic C-H stretching), 2865 (aliphatic C-H stretching), 1694 (C=O stretching), 1602 (aromatic C=C stretching), 1578 (N=N stretching), 1556 (N-H bending of SO2NH group), 1454 (aliphatic C-H bending), 1323, 1144 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.88 (s, 1H), 6.8-8.2 (m, 18H), 2.52 (s, 3H), 2.41 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 163.7, 152.5, 152.3,151.2, 148.8,

137.4, 131.5, 130.6, 130.2, 129.6, 127.7, 145.6, 143.1, 138.2,

126.6, 126.5, 126.1, 125.9, 125.0, 124.4, 121.5, 117.2, 116.3, 11.8, 10.5. MS (ESI) (m/z): 576.1 [M + H] + .

3.5.6. N-(6-Bromo-4-oxo-2-phenyl-4H-quinazolin-3-yl)-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10f)

Orange crystals (71%), m.p. 167-168 oc, Anal. Calcd. For C31H24BrN7O3S: C, 56.88; H, 3.70; N, 14.98%. Found: C, 56.97; H, 3.79; N, 14.76%. IR (KBr, cm-1): 3061 (aromatic C-H stretching), 2855 (aliphatic C-H stretching), 1695 (C=O stretching), 1601 (aromatic C=C stretching), 1571 (N=N stretching), 1556 (N-H bending of SO2NH group), 1452 (aliphatic C-H bending), 1323, 1137 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.92 (s, 1H), 6.6-8.4 (m, 17H), 2.51 (s, 3H), 2.45 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 161.3, 154.5, 153.6, 148.8, 147.3, 145.5, 142.4, 138.3, 137.3, 135.1, 134.1, 131.7, 130.3, 129.4, 129.0, 128.4, 127.1, 124.8, 122.6, 121.6, 121.2,

118.7, 116.45, 11.78, 11.02. MS (ESI) (m/z): 654.2, 656.1 [M] + .

3.5.7. N-(6,8-Dibromo-4-oxo-2-phenyl-4H-quinazolin-3-yl)-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10g)

Orange crystals (78%), m.p. 199-201 oc, Anal. Calcd. For C31H23Br2N7O3S: C, 50.77; H, 3.16; N, 13.37%. Found: C, 50.87; H, 3.21; N 13.46%. IR (KBr, cm-1): 3057 (aromatic C-H stretching), 2850 (aliphatic C-H stretching), 1696 (C=O stretching), 1604 (aromatic C=C stretching), 1581 (N=N stretching), 1553 (N-H bending of SO2NH group), 1450 (aliphatic C-H bending), 1325, 1141 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.85 (s, 1H), 6.5-8.4 (m, 16H), 2.46 (s, 3H), 2.39 (s, 3h). 13C NMR (100 MHz, DMSO-d6): d 162.8, 160.4, 158.5, 155.3,

152.8, 147.6, 146.8, 139.8, 138.4, 134.6, 133.7, 132.7, 130.3, 128.2, 127.6, 127.2, 125.5, 125.2, 124.3, 121.5, 117.2, 115.4, 110.1, 13.1, 11.1. MS (ESI) (m/z): 732.1, 734.1, 735.8 [M] + .

3.5.8. N-[2-(4-Chlorophenyl)-4-oxo-4H-quinazolin-3-yl]-4-(3,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10h)

Orange crystals (73%), m.p. 241-243 oc, Anal. Calcd. For C31H24ClN7O3S: C, 61.03; H, 3.97; N, 16.07%. Found: C,

61.14; H, 3.86; N, 16.13%. IR (KBr, cm-1): 3058 (aromatic C—H stretching), 2863 (aliphatic C—H stretching), 1695 (C=O stretching), 1601 (aromatic C=C stretching), 1574 (N=N stretching), 1557 (N—H bending of SO2NH group), 1455 (aliphatic C—H bending), 1326, 1142 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.77 (s, 1H), 6.5-8.3 (m, 17H), 2.52 (s, 3H), 2.43 (s, 3h). 13C NMR (100 MHz, DMSO-d6): d 162.4, 154.5, 153.6, 152.4, 148.3, 145.4, 143.2, 137.7, 137.1, 135.4, 132.6, 131.7, 129.6, 128.2, 127.7, 127.1, 126.8, 126.0, 125.8, 125.5, 123.4, 122.6,

120.8. 114.1, 13.1, 10.1. MS (ESI) (m/z): 610.2, 612.3 [M] + .

3.5.9. N-[6-Bromo-2-(4-chlorophenyl)-4-oxo-4H-quinazolin-3-yl]-4-(3 ,5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10i)

Orange crystals (78%), m.p. 231-233 0C, Anal. Calcd. For C31H23BrClN7O3S: C, 54.04; H, 3.36; N, 14.23%. Found: C, 54.38; H, 3.46; N, 14.42%. IR (KBr, cm-1): 3057 (aromatic C—H stretching), 2850 (aliphatic C—H stretching), 1697 (C=O stretching), 1602 (aromatic C=C stretching), 1579 (N=N stretching), 1550 (N—H bending of SO2NH group), 1454 (aliphatic C—H bending), 1324, 1141 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.79 (s, 1H), 6.6-8.4 (m, 16H), 2.47 (s, 3H), 2.35 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 161.4, 154.5,

153.2, 149.3, 147.8, 147.2, 143.2, 137.8, 137.1, 135.3, 134.8, 134.0, 132.1, 130.5, 129.3, 127.4, 126.9, 126.2, 125.7, 124.6, 123.5, 118.8, 118.0, 113.3, 11.8, 11.0. MS (ESI) (m/z): 688.2,

690.3, 692.1 [M] + .

3.5.10. N-[6,8-Dibromo-2-(4-chlorophenyl)-4-oxo-4H-quinazolin-3-yl]-4-(3 , 5-dimethyl-1-phenyl-1H-pyrazol-4-ylazo)benzenesulfonamide (10j)

Orange crystals (73%), m.p. 219-220 0C, Anal. Calcd. For C31H22Br2ClN7O3S: C, 48.49; H, 2.89; N, 12.77%. Found: C, 48.64; H, 2.99; N, 12.83%. IR (KBr, cm-1): 3078 (aromatic C—H stretching), 2861 (aliphatic C—H stretching), 1696 (C=O stretching), 1603 (aromatic C=C stretching), 1581 (N=N stretching), 1557 (N—H bending of SO2NH group), 1451 (aliphatic C—H bending), 1323, 1139 (asymmetric and symmetric S=O stretching). 1H NMR (400 MHz, DMSO-d6): d 10.83 (s, 1H), 6.5-8.5 (m, 15H), 2.51 (s, 3H), 2.39 (s, 3H). 13C NMR (100 MHz, DMSO-d6): d 162.6, 158.5, 153.3, 152.7, 152.4, 147.8, 142.3,139.3, 138.5, 138.2, 134.1,

133.5, 132.6, 131.4, 130.7, 129.9, 128.5, 127.1, 125.5, 124.7,

117.6, 118.6, 118.2, 110.8, 13.2, 10.7. MS (ESI) (m/z): 766.1, 767.9, 779.8, 782.2 [M] + .

3.6. In vitro antimicrobial studies

The in vitro antimicrobial activities of all the synthesized compounds were screened for their antibacterial activity against S. aureus, Bacillus subtilis (Gram Positive) and E. coli, P. aeruginosa (Gram Negative), whereas of antifungal against A. niger and A. clavatus using the broth dilution method (Jani et al., 2010). All the ATCC cultures were collected from the Institute of Microbial Technology, Bangalore. 2% Luria broth solution was prepared in distilled water while, pH of the solution was adjusted to 7.4 ± 0.2 at room temperature and sterilized by autoclaving at 15 lb pressure for 25 min. The tested bacterial and fungal strains were prepared in the luria broth and

incubated at 37 oc and 200 rpm in an orbital incubator for overnight. Sample solutions were prepared in DMSO for various concentrations at 250, 200, 150, 100, 50, 25 and 10 pg/mL. The standard drug solution of Streptomycin (antibacterial drug) and Nystatin (antifungal drug) was prepared in DMSO. Serial broth micro dilution was adopted as a reference method. 10 pl solution of test compound was inoculated in 5 mL luria broth for each concentrations respectively and additionally one test tube was kept as control. Each of the test tubes was inoculated with a suspension of standard microorganism to be tested and incubated at 35 oc for 24 h. At the end of the incubation period, the tubes were examined for turbidity. Turbidity in the test tubes indicated that microorganism growth was not inhibited by the antibiotic contained in the medium at the test concentration. The antimicrobial activity tests were performed in triplicate and the deviation for any triplicate results was not more than ±1-5% while average MIC values of the compounds are summarized in Table 2.

4. Conclusion

In extension to our earlier work newer 4-(3,5-dimethyl-1-phe-nyl-1 H-pyrazol-4-ylazo)-N-(2-substituted-4-oxo-4H-quinazo-lin-3-yl)benzenesulfonamide derivatives 10a-10jwere synthesized via classical and microwave irradiation. Microwave irradiations have been verified more preferable over conventional heating. The in vitro study of all the new compounds possesses moderate to excellent antimicrobial activity against bacteria but poor for fungal compared to bacteria.

Acknowledgments

We are thankful to the Principal, V.P. & R.P.T.P. Science College, Vallabh Vidyanagar for providing necessary research facilities. We are also grateful to SICART, Vallabh Vidyana-gar for IR and Mass analysis; CDRI, Lucknow for NMR analyses.

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