SYNTHESIS OF BIOACTIVE HETEROCYCLES FROM 6-AMINO-4-( 2-CHLORO-5-NITROPHENYL )-3-METHYL-1 , 4-DIHYDROPYRANO [ 2 , 3c ] PYRAZOLE-5-CARBONITRILE

Enaminonitrile derivative, 6-amino-4-(2-chloro-5-nitrophenyl)-3-methyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile (1) was synthesized. This compound was utilized as a building block for the synthesis of new 3-methylpyrazolopyran moiety incorporated with different heterocycles involving pyrimidinone, oxazinone, and iminopyrimidine, in addition to novel derivatives including diacetyl derivative (5), benzoyl derivative (6), carbamodithioic acid (10) and urea derivative (13). Spectral techniques, FT-IR, H-NMR and mass spectroscopy and elemental analysis were used to characterize the synthesized compounds. Screening and evaluation of these products as antimicrobial agents showed that the derivatives 5, 6, 10, and 13 possess a potent activity.


INTRODUCTION many heterocycles of synthetic and biological importance
It has been reported that pyran derivatives possess continuation of our efforts to construct heterocyclic hypotensive effect [1], anticancer activity [2], antifungal compounds from pyran derivatives and to study their effect [3,4], plant growth regulation activity [5].
biological potency [38][39][40][41][42][43][44][45] it was of interest to synthesize Pyranopyrazoles are important compounds for the a ring system combine both the pyrazole and the pyran preparation of many biological active heterocyclic moieties which might have good biological activity. compounds [6] and they proved to have useful properties as therapeutics in clinical application [7][8][9]. A literature RESULT AND DISCUSSION survey revealed that pyrazole derivatives have received much attention during the recent years on account of their Chemistry: The previously reported pyranopyrazole utilization as antioxidant [10] antihypertensive [11] derivative1 [46] was allowed to react with different antifungal [12,13] and vasodilator [14]. As well as, reagents aiming to synthesize antimicrobial pyrimidinone derivatives have extensive applications as heterocycles. Reaction of 1 with formic acid afforded the structural units of various biologically important pyrimidinone derivative 2 whose structure was confirmed molecules and as useful intermediates in medicinal from IR spectral data which revealed the absence of chemistry [15] and pyranopyrimidinones compounds absorption bands of C=N and NH groups and the showed considerable pharmaceutical and biological appearance of bands characteristic to carbonyl and NH activities, including anticancer, antitumor, antimalarial, groups at 1682 cm and 3182 cm , respectively. The antibacterial, antihypertensive, anti-inflammatory, H-NMR spectrum showed a singlet at 11.08 ppm, hepatoprotective, cardiotonic, vasodilator, disappeared by D O due to NH group proton. Acid bronchodilator, antifolate and antiallergic activities hydrolysis of the cyano functionality was carried out by [16][17][18][19][20][21][22][23][24][25][26][27][28]. They are also used in the preparation of dyes and addition of concentrated sulphuric acid onto pigments flavoring agents [29][30] and in luminescence pyranopyrazole derivative 1 at room temperature to give chemistry [31]. Over the past decades, significant efforts the amide derivative 3. The structure of the amide 3 was have beendevoted to develop the synthesis of elucidated by the FTIR spectra which showed no pyrimidinethione derivatives [32,33] as they are absorption band of C=N and appearance of a new band considered versatile synthons for the construction of due to C=O group at 1685 cm . [34][35][36][37]. Thus, in view of the above facts and in In our previously work for the synthesis of oxazinone D O due to NH group, a quartet peak owing to CH group derivatives [46], the pyranopyrazole derivative 1 was allowed to react with acetic anhydride and/or benzoyl chloride in neat reactions afforded the pyrazolopyranooxazinones 4a,b. On contrary, herein, the reaction of 1 with acetic anhydride in pyridine gave the diacetyl derivative 5 and benzoylation with benzoyl chloride in dry toluene as a solvent afforded the benzoyl derivative 6. The IR spectra of both products 5 &6 revealed the presence of cyano group absorption that proved no cyclization has occurred (Scheme 1).
To make use of the beneficial role of nucleophilic character of the amino group, it was subjected to react with various electrophiles. Thus, when enaminonitrile 1 was treated with trie thy or tho formate, it gave the imidoformate derivative 7. The latter product was utilized as a precursor for the synthesis of pyrazolo pyranopyrimidine 8 by reaction with hydrazine hydrate in ethanol. The structure of 7 was confirmed from IR spectrumthat showed no absorption frequency of NH 2 group appeared, in addition to the appearance of C=N group band at 1632 cm . The H-NMR spectrum 1 1 showed a singlet at 12.36 ppm which disappeared by 2 2 at 4.34-4.28 ppm and a triplet peak at 1.31-1.28 ppm due to CH protons.The structure of 8 has been elucidated on 3 the basis of IR spectrum which showed a coupling band at 3188, 3119 cm due to NH group and two peaks for 1 2 NH pyrazole and NH imino at 3349 and 3309 cm , 1 respectively. H-NMR spectrum showed a singlet at 1 12.57 ppm (NH) pyrazole group and 10.25 ppm for C=NH. However,when the imidoformate derivative 7 was subjected to react with ammonium hydroxide in methanol, hydrolysis of the imidoformate functionality to the formamide derivative 9 occurred instead of the formation of the pyrimidinone derivative 2. Further, treatment of the enaminonitrile1 with carbondisulfide afforded carbamodithioic acid 10 instead of pyrimidenedithione derivative 11. The IR spectrum of 10 revealed the absorption band attributable for C=N group at 2215 cm -1 and a sharp band at 1390 cm due to C=S group. The antibacterial activity of the The% activity index for the complex was calculated by the synthesized compounds 2, 3, 7, 8, 10and 13 was tested formula as shown below: against a panel of two gram positive bacteria (Staphylococcus aureus, Bacillus subtilis and two Gramnegative bacteria (Escherichia coli, Pseudomonas aeuroginosa). The antifungal activities of the compounds were tested against two fungi (Candida albicans, Aspergillusflavus).
Each compound was dissolved in DMSO and The antimicrobial activity of the synthesized solution of the concentration 1 mg /ml were prepared heterocycles was shown in Table 1  The MIC was determined using the disc diffusion aseptically in the petri dishes containing nutrient agar technique by preparing discs containing 1.9-1000 µg/ml of media (agar 20g + beef extract 3g +peptone 5g) seeded each compound against gram positive Staphylococcus with Staphylococcus aureus, Bacillus subtilis, aureus, Bacillus subtilis and gram negative Escherichia Escherichia coli, Pseudomonas aeuroginosa, Candida coli, Pseudomonas aeuroginosa. The antifungal activities albicans and Aspergillusflavus. The petri dishes were of the compounds were tested against two fold fungi incubated at 36°C and the inhibition zones were recorded Candida albicans, Aspergillus flavus and applying the after 24 h of incubation. Each treatment was replicated protocol. The two fold dilutions of the solution were three times. The antibacterial activity of a common prepared. The microorganism suspensions at 10 CF-U/ ml standard antibiotic ampicillin and antifungal colitrimazole (colony forming unit/ml) concentration were inoculated to was also recorded using the same procedure as above at the corresponding wells. The plates were incubated at the same concentration and solvents.
36°C for 24 h. for the bacteria. The standard antibiotic ampicillin and antifungal colitrimazole was also recorded Experimental: All melting points were determined on an using the same procedure as above at the same electro-thermal apparatus and are uncorrected. The concentration and solvents. At the end of the incubation infrared spectra were recorded in potassium bromide disks period, the minimum inhibitory concentration (MIC) on PyeUnicam SP3-300 and Shimdazu FTIR 8101PC values were recorded as the lowest concentration of the Infrared spectrophotometers. The H-NMR was recorded substance that had no visible turbidity. Control on a Varian Mercury VX-300 NMR spectrometer. H-NMR experiments with DMSO and uninoculated media were run spectra were run at 300MHz and on a Varian Gemini 200 parallel to the test compounds under the same condition.
MHz, Bruker AC 200 MHz using TMS as internal standard The MIC measurement of the synthesized in deuterated chloroform (CDCl ) or deuterated dimethyl heterocyclic compounds was shown in Table 2: sulfoxide (DMSO-d ). Chemical shifts are quoted in