Indian Journal of Chemistry Vol. 53B, February 2014, pp 227-237 Synthesis, antibacterial and antifungal activities of some new azo anils containing pyrazole moiety S Sharma*a, Jasvir Kaurb, Sandeep Kaurb & Poonam Sharmaa aDepartment of Plant Breeding & Genetics, Punjab Agricultural University, Ludhiana 141 004, India bDepartment of Chemistry, Punjab Agricultural University, Ludhiana 141 004, India E-mail: [email protected] Received 11 February 2013; accepted (revised) 31 October 2013 A series of azo compounds namely 3-(Phenylazo) benzaldehyde 1a-f, 3-(4-Nitrophenylazo) benzaldehyde 3a-f and 3- (1,5-Dimethyl–3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl-azo) benzaldehyde 6 were synthesized and then azo anils viz. 3-(Phenylazo)-1,5 dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H pyrazol-4-yl imino methyl benzene 2a-f, 4a-f and 7-9 have been synthesized from azo compounds by reacting with corresponding amines. All the compounds synthesized by conventional method are also prepared by using microwave irradiation method and are characterized by spectroscopic techniques (UV, FTIR and 1H NMR). The synthesized compounds have been screened for antimicrobial activity against bacteria viz. Mesorhizobium sp., Bacillus sp. and Pseudomonas sp., fungus (Ascochyta blight) and yeast (Sacchromycis cerevisiae). The azo anils show minor to moderate activity against bacteria and no activity against fungus and yeast. The activity shown by some compounds is due to substitution of chloro, methoxy or nitro group on phenyl ring or due to some heterocyclic moiety. Keywords: Azo anils, azo compounds, microwave irradiation, Mesorhizobium sp., Bacillus sp., Pseudomonas sp. Azo anil formation is of major importance in and pharmaceutical chemistry with several biological biological processes as many of these involve the applications. It has been suggested that azomethine initial binding of carbonyl compounds to an enzyme linkage might be responsible for the biological through imine formation. Among the organic reagents activities of Schiff bases. Therefore, in the present actually used, imines possess excellent characteristics, study, some new azoanils with azomethine linkage structural similarities with natural biological have been synthesized by conventional and substances, relatively simple preparation procedure microwave methods and evaluated for their microbial and synthetic flexibility that enables design of suitable studies. structural properties. Carbon-nitrogen double bond is widely distributed in nature, in the form of biological Results and Discussion compounds which are important for the vital Synthesis of azo compounds 1a-f was carried out metabolism of the living organisms and in various by the reaction of diazonuim salt of aniline with synthetic compounds of pharmaceutical and benzaldehyde, 2-methoxy benzaldehyde, 4-methoxy agricultural importance. Azo dyes constitute one of benzaldehyde, 2-chlorobenzaldehyde, 4-chlorobenz- the largest and most varied groups of synthetic aldehyde and 3-nitrobenzaldehyde respectively organic dyes in use today1. Azo compounds are highly (Scheme I). The physical data of azo compounds and important, well known and widely used substances in azo anils is given in Table I. The structure of these the textile, paper, colouring agents for foods and compounds were confirmed by FTIR spectroscopy cosmetics industries2,3. Furthermore, azo compounds that recorded peaks between 1410-1417 cm-1 due to were reported to show a variety of biological N=N stretching. These azo compounds were reacted activities including antibacterial4, antifungal5, with 4-aminophenazone and respective azo anils 2a-f pesticidal, antiviral and anti inflammatory activities. were formed (Scheme I) that was characterized by Azomethine function is endowed with multiform UV-visible, FTIR and 1H NMR spectroscopy. UV- reactivity and particularly is able to react with thiol visible spectra recorded λmax between 267-293 and groups, thus it can establish easily some kind of link 338-357 nm, FTIR spectra recorded peaks between with enzymatic or receptorial proteins. Schiff bases 1660-1678 cm-1 due to C=N and 1413-1459 cm-1 due form a significant class of compounds in medicinal to N=N stretching. 1H NMR spectra showed a singlet 228 INDIAN J. CHEM., SEC B, FEBRUARY 2014 Scheme I between δ 8.09-8.35 due to hydrogen of HC=N group. between 260-298 and 330-389 nm, FTIR spectra Similarly the azo compounds 3a-f were prepared by showed peaks between 1660-1671 cm-1 due to C=N the reaction of diazonium salt of 4-nitro aniline with and 1405-1459 cm-1 due to N=N stretching and 1H respective aldehydes viz. benzaldehyde, 2-methoxy NMR spectra recorded a singlet between δ 8.11-8.35 benzaldehyde, 4-methoxy benzaldehyde, 2-chloro- due to hydrogen of HC=N group. An azo compound 6 benzaldehyde, 4-chlorobenzaldehyde and 3-nitrobenz- was prepared from the diazonium salt of aldehyde (Scheme II). The structure of these 4-aminophenazone and benzaldehyde (Scheme III). compounds were confirmed by FTIR spectroscopy The structure of this compound was confirmed by that recorded peaks between 1409-1415 cm-1 due to FTIR spectroscopy that recorded a peak at 1410 cm-1 N=N stretching. Then these synthesized azo due to N=N stretching. It was reacted with different compounds were reacted with 4-aminophenazone and amines like aniline, 4-nitro aniline and respective azo anils 4a-f were formed (Scheme II) 4-aminophenazone to obtain respective azo anils 7, 8 that was confirmed by using UV-visible, FTIR and 1H and 9 (Scheme IV). The structures of these NMR spectroscopy. UV-visible spectra recorded λmax compounds were characterized by UV-visible, FTIR SHARMA et al.: NEW AZO ANILS 229 Table I — Physical data of synthesized compounds Compd R R1 R2 Molecular Formula m.p (°C) Yield (%) C H N O 1a H H H 13 10 2 72-74 72 2a H H H C24H21N5O 142-144 50 C H N O 1b OCH3 H H 14 13 2 2 85-87 80 2b OCH3 H H C25H23N5O2 80-82 75 C H N O 1c H H OCH3 14 13 2 2 93-95 75 2c H H OCH3 C25H23N5O2 85-89 70 C H N OCl 1d Cl H H 13 9 2 100-102 70 2d Cl H H C24H20N5OCl 105-107 67 C H N OCl 1e H H Cl 13 9 2 90-92 70 2e H H Cl C24H20N5OCl 95-97 70 C H N O 1f H NO2 H 13 9 3 3 85-87 80 2f H NO2 H C24H20N6O3 80-82 65 C H N O 3a H H H 13 9 3 3 105-108 70 4a H H H C24H20N6O3 67-69 65 C H N O 3b OCH3 H H 14 11 3 4 140-142 70 4b OCH3 H H C25H22N6O3 152-154 55 C H N O 3c H H OCH3 14 11 3 4 102-106 70 4c H H OCH3 C25H22N6O3 79-81 74 C H N O Cl 3d Cl H H 13 8 3 3 105-107 75 4d Cl H H C24H19N6O3Cl 112-114 72 C H N O Cl 3e H H Cl 13 8 3 3 76-78 70 4e H H Cl C24H19N6O3Cl 85-88 47 C H N O 3f H NO2 H 13 8 4 5 115-120 70 4f H NO2 H C24H19N7O5 79-82 59 C H N O 6 H H H 18 16 4 2 87-89 70 7 H H H C24H21N5O 92-95 65 8 H H H C24H20N6O3 120-124 65 9 H H H C26H21N7O5 106-108 55 and 1H NMR spectroscopy. UV-visible spectra about 5-30% increase in yield in case of microwave recorded λmax between 273-298 and 332-375 nm, irradiation method (Table II). FTIR spectra recorded peaks between 1660-1676 cm-1 due to C=N and 1400-1412 cm-1 due to N=N Antimicrobial testing stretching. 1H NMR spectra showed a singlet between The synthesized compounds 2a-f, 4a-f, 7-9 were δ 7.80-8.28 due to hydrogen present on HC=N group. screened for their inhibitory effect on the growth of The synthesized azo anils were purified by bacteria (Mesorhizobium sp., Bacillus sp. and recrystallization and the purity of compounds was Pseudomonas sp.), fungus (Ascochyta blight) and checked by thin layer chromatography. yeast (Sacchromycis cerevisiae) at various Azo anils synthesized by conventional method concentrations. were also prepared by using microwave irradiation method from the azo compounds synthesized by Anti-bacterial activity conventional method6. It was observed that the The results shown in Tables III, IV and V revealed reaction completed in maximum 10 minutes by that the majority of synthesized compounds exhibited microwave irradiation method which was completed varying degrees of inhibition against the in 9 hr in case of conventional method and there was Mesorhizobium sp., Bacillus sp. and Pseudomonas sp. 230 INDIAN J. CHEM., SEC B, FEBRUARY 2014 Scheme II The compounds 2a, 2c, 2f, 4b, 4d, 4e, 4f, and 9 group on phenyl ring were effective against all the containing pyrazole moiety having no substitution on tested bacteria. Compound 2d having 2-chloro group phenyl ring exhibited no activity against tested on phenyl ring was found effective against Bacillus bacteria even upto 5000 µg/mL concentration. and Pseudomonas sp. The data revealed that Compound 2a without any substitution on phenyl ring compounds 7 and 8 were not effective against was effective against Bacillus sp. only at 4000 and Bacillus sp. upto 5000 µg/mL concentration. While 5000 µg/mL concentration. This compound exihibited the compound 7 showed activity against no activity against Mesorhizobium sp. and Pseudomonas sp. and the compound 8 exhibited some Pseudomonas sp. upto 5000 µg/mL concentration. activity against Mesorhizobium sp. However all Compounds containing 2-methoxy 2b and 4-chloro 2e compounds were less effective as compared to SHARMA et al.: NEW AZO ANILS 231 Scheme III streptomycin.