Scientific paper
A Facile One-pot Synthesis and Antimicrobial Activity of Pyrido [2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones
Thoraya A. Farghaly, Sayed M. Riyadh, Magda A. Abdallah* and Mohamed A. Ramadan
Department of Chemistry, Faculty of Science, University of Cairo, Giza, 12613, Egypt * Corresponding author: E-mail: abdallah_197554@yahoo.com Received: 19-08-2010
Abstract
A series of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones (8) has been synthesised via reaction of 5-substituted-2-thioxo-2,3-dihydro-1_ff-pyrido[2,3-d]pyrimidin-4-one (3) or its methylthio derivative 4 with hydrazonoyl chlorides 5. Alternative syntheses of products 8 were carried out either by reaction of enaminone 1 with 7-amino-1,3-disubstitu-ted[1,2,4]triazolo[4,3-a]pyrimidin-5-one (10) or via the Japp-Klingemann reaction of compound 13. Both conventional thermal and microwave irradiation techniques were used for synthesis of the target products 8 and a comparative study of these techniques using triethylamine or chitosan, as basic catalysts, was carried out. The mechanisms of the reactions under investigation are discussed. In addition, the antimicrobial activity of the newly synthesized products was evaluated.
Keywords: Enaminone, 2-thioxo-2,3-dihydro-1_ff-pyrido[2,3-d]pyrimidin-4-one, hydrazonoyl chlorides, microwave irradiation, chitosan, antimicrobial activity.
1. Introduction
[1,2,4]Triazolo[4,3-a]pyrimidines are pharmacological scaffolds displaying a wide range of biological activities such as antitumor,1 human A3 adenosine receptor,2 antibacterial,3 CNS depressant,4 antiallergy,5 and anti-inflammatory.6 In the field of coordination chemistry, [1,2,4]triazolo[4,3-a]pyrimidine can be used as a bridging ligand.7 On the other hand, pyridopyrimidi-nes, another class of heterocyclic compounds, can be used as active modulators of cannabinoid-1 receptor (CB1R).8 Fusion of [1,2,4]triazole ring to pyridopyrimi-dines tends to expose novel biological activities. Based on these findings and as a part of our research program aiming at synthesis of heterocyclic systems with biological and pharmacological activities,915 we became interested in extending the scope of this approach for synthesis of novel pyrido[2,3-d][1,2,4]triazolo[4,3-a] pyrimidin-5-ones incorporating the [1,2,4]triazolo [4,3-a]pyrimidine moiety. Also, in this context the antimicrobial evaluation of the newly synthesized compounds was performed.
2. Results and Discussion
The starting reactant 3, namely 5-substituted-2-thio-xo-2,3-dihydro-1H-pyrido[2,3-d]pyrimidin-4-one which has not previously been reported, was prepared by reaction of 3-[3-(dimethylamino)-2-propenoyl]-1,7-diphenyl-1,5-dihydro[1,2,4]triazolo[4,3-a]pyrimidin-5-one (1)16 with 6-amino-2-thioxo-2,3-dihydropyrimidin-4(1H)-one (2)17 under reflux in acetic acid (Scheme 1). Also, the new compound, 2-methylthio derivative 4 was prepared by reaction of 3 with methyl iodide in dimethylformamide in the presence of anhydrous potassium carbonate at room temperature (Scheme 1).
The reaction of 3 with the appropriate hydrazonoyl chlorides 5a-l was carried out in dioxane in the presence of triethylamine under reflux until all hydrogen sulfide gas ceased to evolve (Scheme 2). After work up the reaction gave in each case, only one isolable product as evidenced by TLC analysis of the crude product. The assigned structure 8 for the isolated products is based on microanalysis and spectral (IR, 1H NMR, MS) data. For example, the IR spectra of products 8 revealed in each ca-
Scheme 1
se an absorption band at v (1751-1693) cm-1 due to the carbonyl group of the substituent at position-3. 1H NMR spectra showed no signals assignable to the 2 NH groups in compound 3 and instead revealed the appearance of signals due to the protons of the acetyl, ester, and anilide sub-stituents at position-3 (see Experimental). The mass spectra revealed in each case a molecular ion peak at the expected m/z value.
To account for the direct formation of products 8a-l from reaction of 3 with 5a-l, the mechanism outlined in Scheme 2 is proposed. The reaction starts with the forma-
pn
Compd. no-	R-	Ar	Compd. rto-	R"	Ar	Compd. no.	R'	Ar
Sa, an	CHjCO	CJt,	5«, Be	CO-Et	C,H,	5i. Bi	PhNHCO	
5 b. ill	CHJOO	4-CHjCtMj	Sf,«	co.ei	a<HjC,Mt	sa- es	PhNHCO	4-CHJC,H<
5c, Be	CHJCQ	J-CLCfiHj	5G.Bg	COjE!	4-CICfiH4	5 k. Bk	PhNHCO	4-CIC6H4
5d, SO	CHjCO	■1 NOzC,	5h, >11	CO:E!	4-NOiOsH,	51. Si	PhNHCO	4-NO:C5H,
Scheme 2
tion of thiohydrazonates 6a-l which undergo Smiles rearrangement18,19 to yield the corresponding thiohydrazides 7a-l. The latter compounds undergo in situ cyclization with elimination of hydrogen sulfide gas to give 8a-l as the end products (Scheme 2). The regioselective cycliza-tion of the thiohydrazides 7a-l was further evidenced by an alternative synthesis of 8 via reaction of 4 with hydra-zonoyl chlorides 5a,e,i under the same conditions. Thus, treatment of 4 with 5a,e,i in dioxane in the presence of triethylamine under reflux led to formation of products identical in all respects (mp, mixed mp, IR) with products 8a,e,i (Scheme 2). The reaction of 4 with 5a,e,i proceeds via the formation of the amidrazones 9a,e,i, which in turn, undergo cyclization with elimination of methanethiol to give 8a,e,i as end products (Scheme 2). The intermediates 6a-l, 7a-l, and 9a,e,i could not be isolated in any case, which indicates that such intermediates are consumed in situ under the reaction conditions employed.
Further evidence for the assigned structure of compounds 8 was obtained via alternative synthesis of these products. Thus, reaction of 7-amino-3-acetyl-1-phenyl [1,2,4]triazolo[4,3-a]pyrimidin-5(1#)-one (l0)20 with enaminone 1 in acetic acid under reflux gave a product identical in all respects (mp, mixed mp, IR) with the isolated product 8a (Scheme 3).
Scheme 3
Final evidence for the assigned structure of the target products 8a-l was based on alkylation of 3 with chlo-roactivemethylene compound 12 followed by coupling obtained with diazonium salt.18,19,21 Thus, reaction of 3 with 3-chloropentane-2,4-dione22-24 12 in ethanol in the presence of triethylamine at room temperature yielded substitution product 13 (Scheme 4). The structure of the new product 13 was elaborated by its spectral data (IR, 1H NMR, and MS) and elemental analysis. For example, the 1H NMR spectrum showed two characteristic singlet signals near d 2.4 and 4.9 ppm assigned to the protons of CH3CO and SCH groups, in addition to the signals of the
Scheme 4
=NH and aromatic protons (see Experimental). Treatment of compound 13 with phenyldiazonium chloride in etha-nol in the presence of sodium acetate at low temperature (0-5 °C) led to formation of a single substance as evidenced by TLC analysis of the crude product. The microanalyses and mass spectral data of the isolated product were consistent with structure 8a (Scheme 4).
The formation of the product 8a obtained by the reaction sequence outlined in Scheme 4, was reasonably formed by Japp-Klingemann21 elimination of the acetyl group during the azo coupling reaction of compound 13, to form the corresponding thiohydrazonate 6a. The latter undergo Smiles rearrangement18,19 as mentioned above to give the thiohydrazide 7a, which in turn undergo in situ cyclization, to give 8a, as the end product (Scheme 4).
Finally, we use microwave irradiation as an alternative method for the synthesis of products 8a, 8e, and 8i using the same reaction sequence outlined in Scheme 1. It is noteworthy that the catalyst used in this method may be either triethylamine or chitosan, i.e., a copolymer containing both glucoseamine units and acetylglucoseamine units, which is a very efficient and environmentally benign heterogeneous basic catalyst. In Table 1 the reaction results (time, % yield) are compared with those of the traditional thermal procedure using triethylamine as basic catalyst.
As shown in Table 1, the use of microwave irradiation substantially reduced the reaction times from hours to minutes and appreciably increased the yield of the products. Also, chitosan can be used as an ecofriendly basic catalyst for preparation of the desired products 8a,e,i in high yield under thermal heating or microwave irradiation.
3. Antimicrobial Activity
The compounds 8a-g,k were tested for their antimicrobial activities using two bacteria species namely, Gram (+) bacteria as Staphylococcus aureus Sa and Gram (-) bacteria as Esherichia coli Ec. The organisms were tested against the activity of solutions of concentration 20 mg/mL of each compound and using an inhibition zone diameter (IZD) in (mm/mg sample) as criterion for the antimicrobial activity.25,26 The bactericide Tetracycline was used as reference to evaluate the potency of the tested compounds under the same conditions. The results are depicted in Table 2. The tested products (8a-g,k) exhibited antimicrobial and antipseudomonal effect. Products 8a,c,e have moderate activity against both of Gram-positive and Gram-negative bacteria.
Table 1. Formation of 8a, 8e, and 8i using microwave and conventional heating techniques
Compound Microwave irradiation	Thermal heationg
number Time Yield (%) Yield (%)	Time Yield (%) Yield (%)
(Minutes) (Chitosan) (TEA)	(Hours) (Chitosan) (TEA)
8a 4 93 92	2 88 82
8e 4 95 93	2 90	85
8i 4 82 82	2 81 80
Table 2. Antimicrobial activity of products 8*
Sample no. Inhibition zone diameter	Sample no. Inhibition zone diameter
(mm / mg sample)	(mm / mg sample)
Ec (G-)	Sa (G+)	Ec (G-) Sa (G+)
8a	14	14	8f	11	11
8b	11	12	8g	11	11
8c	16	16	8k	10	10
8d	11	12	Tetracycline	30	30
8e	12	13			
* A solution of 20.0 mg/ml was tested Ec: Esherichia coli; (G ): Gram negative bacteria
Sa: Staphylococcus aureus; (G+): Gram positive bacteria Tetracycline used as standard antibacterial agent
4. Conclusions
Pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones 8, with an incorporated [1,2,4]triazolo[4,3-a]pyrimidine moiety, have been prepared via one-pot reaction of pyri-dopyrimidine thione 3 or its methylthio derivative 4 with hydrazonoyl chloride 5 using triethylamine or chitosan as basic catalysts. Microwave irradiation and conventional thermal heating techniques were employed for carrying out these reactions. Some of the newly synthesized products 8 have a mild effect against Sa (G+) and Ec (G-) bacteria.
5. Experimental Section
All melting points were determined on an electrothermal Gallenkamp apparatus and they are uncorrected. Solvents were generally distilled and dried by standard literature procedures prior to use. The IR spectra were measured on a Pye-Unicam SP300 Infrared Spectrophotometers in potassium bromide discs. The 1 H NMR spectra were recorded on a Varian Mercury VXR-300 spectrometer (300 MHz) and the chemical shifts were related to that of the solvent DMSO-d6. The mass spectra were recorded on a GCMS-Q1000-EX Shimadzu and GCMS 5988-A HP spectrometers, the ionizing voltage was 70 eV. Elemental analyses were carried out by the Microanalytical Center of Cairo University, Giza, Egypt. Microwave experiments were carried out using CEM Discover Labmate microwave apparatus (300 W with Chem. Driver Software).
The antimicrobial activity of products 8 was evaluated at the Microanalytical Center of Cairo University. Compounds 1,16 2,17 10,20, 12,22-24 and hydrazonoyl chlorides 527-33 were prepared following literature methods.
Synthesis of 5-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-2-thioxo-2,3-dihydro-1_ff-pyrido[2,3-d]pyrimidin-4-one (3)
A mixture of 3-[3-(dimethylamino)-2-propenoyl]-1,7-diphenyl-1,5-dihydro[1,2,4]triazolo[4,3-a]pyrimidin-5-one (1) (3.85 g, 10 mmol) and 6-amino-2-thioxo-2,3-
dihydropyrimidin-4(1H)-one (2) (1.43 g, 10 mmol) in acetic acid (40 mL) was refluxed for 6 hours. The reaction mixture was cooled and diluted with methanol and the solid product was collected by filtration and recrystallized from dioxane to give 3.
Yellow crystals [3.72 g, 80%], mp > 300 °C; IR (KBr) u 3261, 3245 (2 NH), 1677, 1662 (2 CO), cm1; 1H NMR (300 MHz, DMSO-d6) S 6.70 (s, 1H, pyrimidine-H), 7.49-8.20 (m, 10H, Ar-H), 8.29 (d, 1H, J = 4.5 Hz, pyridine-H), 8.48 (d, 1H, J = 4.5 Hz, pyridine-H), 12.72 (s, 1H, NH), 13.34 (s, 1H, NH) ppm; MS, m/z (relative intensity) 465 (M+, 40), 287 (20), 178 (40), 77 (100). Anal. Calcd. for C24H15N7O2S (465.10): C, 61.93; H, 3.25; N, 21.06; S, 6.829. Found: C, 61.82; H, 3.44; N, 21.12; S, 6.79%.
Synthesis of 2-methylsulfanyl-5-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a] pyrimidin-3-yl)]-3ff-pyrido[2,3-d]pyrimidin-4-one (4)
To a stirred solution of 5-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-2-thioxo-2,3-dihydro-1H-pyrido[2,3-d]pyrimidin-4-one (3) (0.47 g, 1 mmol) in dimethylformamide (10 mL) was added anhydrous potassium carbonate (0.21 g, 1.5 mmol), and methyl iodide (0.14 g, 1 mmol). The reaction mixture was stirred overnight at room temperature then poured into ice-water. The solid formed was filtered, washed with water, dried and recrystallized from dioxane to give compound 4 as yellow solid, mp > 300 °C; IR (KBr) u 3325 (NH), 1690, 1666 (2 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) S 2.58 (s, 3H, CH3), 6.68 (s, 1H, pyrimidine-H), 7.25-8.13 (m, 10H, Ar-H), 8.24 (d, J = 5 Hz, 1H, , pyridine-H), 8.31 (d, J = 5 Hz, 1H, pyridine-H), 11.94 (s, 1H, NH) ppm. Anal. Calcd. for C25H17N7O2S (479.52): C, 62.62; H, 3.57; N, 20.45; S, 6.69. Found: C, 62.37; H, 3.28; N, 20.32; S, 6.51%.
Synthesis of pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimi-din-5-one derivatives (8a-l)
Method A: To a mixture of equimolar amounts of 3 and the appropriate hydrazonoyl chloride 5a-l (1 mmol of each) in dioxane (15 mL) was added triethylamine (0.14
mL, 1 mmol). The reaction mixture was refluxed till all of the starting materials had disappeared and hydrogen sulfide gas ceased to evolve (2 h, monitored by TLC). The solvent was evaporated and the residue was treated with methanol. The solid formed was filtered and recrystallized from dioxane to give compounds 8a-l.
Method B: To a mixture of equimolar amounts of 4 and the appropriate hydrazonoyl chloride 5a,e,i (1 mmol of each) in dioxane (15 mL) was added triethylamine (0.14 mL, 1 mmol). The reaction mixture was refluxed until methanethiol gas ceased to evolve (2 h, monitored by TLC). The solvent was evaporated and the residue treated with methanol. The solid that formed was filtered and re-crystallized from dioxane to give products identical in all respects (mp, mixed mp and IR) with 8a,e,i..
Method C: To a solution of 3 and the appropriate hydrazonoyl chloride 5a,e,i (1 mmol of each) in dioxane (15 mL) was added triethylamine (0.14 mL, 1 mmol) at room temperature. The reaction mixture was irradiated in a pressurized microwave (17.2 Bar, 140 °C) for 4 min. at a power of 300 W. After cooling, dil. HCl was added till the pH became acidic, and the solid product was collected and recrystallized from dioxane to give products 8a,e,i.
Method D: To a solution of 3 (0.13 g, 1 mmol) and the appropriate hydrazonoyl chloride 5a,e,i (1 mmol of each) in dioxane (15 mL) was added chitosan (0.1 g) at room temperature. The reaction mixture was irradiated under constant pressure (17.2 Bar, 140 °C) for 4 min. at a power of 300 W. The hot solution was filtered to remove chitosan. After cooling, dil. HCl was added till the pH became acidic, and the solid product was collected and re-crystallized from dioxane to give products 8a,e,i. The physical constants together with the spectral data of products 8 a-l are listed below:
3-Acetyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-phenyl-1,5-dihy-dropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidm-5-one
(8a)
Yellow crystals, mp 195-197 °C; IR (KBr) u 1733, 1698, 1650 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) S 2.81 (s, 3H, COCH3), 6.69 (s, 1H, pyrimidine-H), 7.43-8.33 (m, 15H, Ar-H), 7.88 (d, J = 4.5 Hz, 1H, pyridi-ne-H), 8.79 (d, J = 4.5 Hz, 1H, pyridine-H) ppm; 13C NMR (300 MHz, DMSO-d6) S 30.3, 123.9, 124.2, 124.5, 125.9, 126.4, 126.5, 128.2, 128.4, 128.8, 129.1, 129.4, 129.8, 139.8, 142.2, 143.9, 147.4, 147.7, 148.8, 152.4, 153.3, 155.3, 159.1, 159.3, 167.7, 168.1, 176.4 ppm; MS, m/z (relative intensity) 591 (M+, 25), 408 (20), 233 (40), 91 (100), 77 (60). Anal. Calcd. for C33H21N9O3 (591.18): C, 67.00; H, 3.58; N, 21.31. Found: C, 67.09; H, 3.48; N, 21.19%.
3-Acetyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-methylphenyl)-
1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimi-din-5-one (8b)
Dark orange crystals, mp 285-287 °C; IR (KBr) u 1726, 1691, 1654 (3 CO), cm-1; :H NMR (300 MHz, DMSO-d6) S 2.44 (s, 3H, Ar-CH3), 2.79 (s, 3H, COCH3), 6.67 (s, 1H, pyrimidine-H), 7.43-7.70 (m, 10H, Ar-H), 7.86 (d, J = 5 Hz, 1H, pyridine-H), 8.11 (d, J = 8 Hz, 2H, Ar-H), 8.30 (d, J = 8 Hz, 2H, Ar-H), 8.77 (d, J = 5 Hz,1H, pyridine-H) ppm; MS, m/z (relative intensity) 605 (M+, 23), 233 (17), 132 (22), 91 (100), 77 (56). Anal. Calcd. for C34H23N9O3 (605.19): C, 67.43; H, 3.83; N, 20.82. Found: C, 67.29; H, 3.72; N, 21.03%.
3-Acetyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-chlorophenyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-
one (8c)
Yellow crystals, mp 190-192 °C; IR (KBr) u 1730,
1697,	1647 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) S 2.81 (s, 3H, COCH3), 6.68 (s, 1H, pyrimidine-H), 7.31-7.75 (m, 10H, Ar-H), 7.88 (d, J = 8 Hz, 2H, Ar-H), 8.19 (d, J = 8 Hz, 2H, Ar-H), 8.20 (d, J = 4.5Hz, 1H, pyridine-H), 8.79 (d, J = 4.5 Hz, 1H, pyridine-H) ppm; MS, m/z (relative intensity) 627 (M++2, 14), 625 (M+, 18), 129 (34), 103 (46), 91 (100), 77 (70). Anal. Calcd. for C33H20ClN9O3 (625.14): C, 63.31; H, 3.22; N, 20.14. Found: C, 63.19; H, 3.28; N, 20.25%.
3-Acetyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-nitrophenyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-
one (8d)
Yellow crystals, mp > 300 °C; IR (KBr) u 1738,
1698,	1655 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) S 2.82 (s, 3H, COCH3), 6.69 (s, 1H, pyrimidine-H), 7.46-7.79 (m, 10H, Ar-H), 8.47 (d, J = 8 Hz, 2H, Ar-H), 8.52 (d, J = 8 Hz, 2H, Ar-H), 7.79 (d, J = 4.5 Hz, 1H, pyridine-H), 8.87 (d, J = 4.5 Hz, 1H, pyridine-H) ppm; MS, m/z (relative intensity) 636 (M+, 25), 465 (60), 129 (40), 103 (35), 91 (100), 77 (50). Anal. Calcd. for C33H20N10O5 (636.16): C, 62.26; H, 3.17; N, 22.00. Found: C, 62.19; H, 3.24; N, 22.15%.
Ethyl 5-oxo-6-[(1,7-diphenyl-1,5-dihydro-5 -oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-phenyl-1,5-dihy-dropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (8e)
Yellow crystals, mp 215-217 °C; IR (KBr) u 1750, 1707, 1645 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) S 1.44 (t, J = 7 Hz, 3H, CH3), 4.57 (q, J = 7 Hz, 2H, CH2), 6.69 (s, 1H, pyrimidine-H), 7.44-8.30 (m, 15H, Ar-H), 7.87 (d, J = 5 Hz, 1H, pyridine-H), 8.77 (d, J = 5 Hz, 1H, pyridine-H) ppm; 13C NMR (300 MHz, DMSO-d6) S 30.6, 35.6, 122.9, 124.1, 124.8, 125.7, 126.6, 126.9, 127.9, 128.4, 128.9, 129.3, 129.8, 129.9, 139.5, 142.7, 143.9, 147.7, 147.9, 148.8, 152.9, 153.8, 155.4, 159.6,
159.9, 167.8, 168.6, 177.8 ppm; MS, m/z (relative intensity) 621 (M+, 25), 212 (75), 157 (20), 91 (100), 77 (80). Anal. Calcd. for C34H23N9O4 (621.19): C, 65.70; H, 3.73; N, 20.28. Found: C, 65.59; H, 3.68; N, 20.39%.
Ethyl 5-oxo-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-methylphenyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimi-dine-3-carboxylate (8f)
Yellow crystals, mp 256-258 °C; IR (KBr) u 1753, 1709, 1687 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) 8 1.42 (t, J = 7 Hz, 3H, CH3), 2.39 (s, 3H, Ar-CH3), 4.56 (q, J = 7 Hz, 2H, CH2), 6.69 (s, 1H, pyrimid3ne-H), 7.55-7.77 (m, 10H, Ar-H), 7.85 (d, J = 5 Hz, 1H, pyridi-ne-H,), 8.11 (d, J = 8 Hz, 2H, Ar-H), 8.31 (d, J = 8 Hz, 2H, Ar-H), 8.78 (d, J = 5 Hz, 1H, pyridine-H) ppm; MS, m/z (relative intensity) 635 (M+, 25), 591 (25), 261 (40), 171 (20), 91 (100), 77 (60). Anal. Calcd. for C35H25N9O4 (635.20): C, 66.14; H, 3.96; N, 19.83. Found: C, 65.99; H, 3.88; N, 20.03%.
Ethyl 5-oxo-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-chlorophenyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (8g)
Yellow crystals, mp 175-177 °C; IR (KBr) u 1749, 1698, 1662 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6)
81.43	(t, J = 7 Hz, 3H, CH3), 4.56 (q, J = 7 Hz, 2H, CH2),
6.68	(s, 1H, pyrimidine-H), 7.55-8.30 (m, 10H, Ar-H), 8.31 (d, J = 8 Hz, 2H, Ar-H), 8.35 (d, J = 8 Hz, 2H, Ar-H), 8.38 (d, J = 5 Hz, 1H, pyridine-H), 8.78 (d, J = 5 Hz, 1H, pyridine-H) ppm; MS, m/z (relative intensity) 657 (M++2, 10), 655 (M+, 25), 281 (20), 194 (10), 91 (100), 77 (60). Anal. Calcd. for C34H22ClN9O4 (655.15): C, 62.25; H, 3.38; N, 19.22. Found: C, 62.19; H, 3.30; N, 19.13%.
Ethyl 5-oxo-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-nitrophenyl)-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxylate (8h)
Yellow crystals, mp > 300 °C; IR (KBr) u 1751, 1706, 1669 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6)
81.44	(t, J = 7 Hz, 3H, CH3), 4.56 (q, J = 7 Hz, 2H, CH2),
6.69	(s, 1H, pyrimidine-H), 7.56-8.29 (m, 10H, Ar-H), 8.38 (d, J = 8 Hz, 2H, Ar-H), 8.41 (d, J = 8 Hz, 2H, Ar-H), 7.84 (d, J = 4.5 Hz, 1H, pyridine-H), 8.82 (d, J = 4.5 Hz, 1H, pyridine-H) ppm; MS, m/z (relative intensity) 666 (M+, 25), 281 (20), 194 (10), 91 (100), 77 (60). Anal. Calcd. for C34H22N10O6 (666.17): C, 61.26; H, 3.33; N, 21.01. Found: C, 61.19; H, 3.38; N, 21.11%.
V3,1-Diphenyl-5-oxo-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-1,5-dihy-dropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (8i)
Yellow crystals, mp 170-172 °C; IR (KBr) u 3388
(NH), 1697, 1688, 1651 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) 86.65 (s, 1H, pyrimidine-H), 7.21-8.35 (m, 20H, Ar-H), 7.76 (d, J = 5.5 Hz, 1H, pyridine-H), 8.80 (d, J = 5.5 Hz, 1H, pyridine-H), 11.12 (s, 1H, NH) ppm; 13C NMR (300 MHz, DMSO-d6) 8 108.4, 120.3, 120.9, 121.5, 122.7, 124.1, 124.7, 125.7, 126.5, 126.9, 127.6, 128.4, 128.9, 129.1, 129.5, 129.9, 139.3, 142.7, 143.8, 145.9, 147.5, 147.8, 148.6, 152.7, 153.8, 155.4, 159.6, 163.9, 167.8, 168.6 ppm; MS, m/z (relative intensity) 668 (M+, 25), 548 (20), 120 (100), 91 (80), 77 (75). Anal. Calcd. for C38H24N10O3 (668.20): C, 68.26; H, 3.62; N, 20.95. Found: C, 68.09; H, 3.58; N, 21.09%.
5-Oxo-V3-phenyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-methylp-henyl)-1,5-dihydropyrido[2,3-rf][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (8j)
Yellow crystals, mp 202-204 °C; IR (KBr) u 3386 (NH), 1695, 1682, 1650 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) 8 2.22 (s, 3H, Ar-CH3), 6.58 (s, 1H, pyrimidine-H), 77.13-8.25 (m, 19H, Ar-H), 7.85 (d, J = 5 Hz, 1H, pyridine-H), 8.74 (d, J = 5 Hz, 1H, pyridine-H), 11.24 (s, 1H, NH) ppm; MS, m/z (relative intensity) 682 (M+, 25), 562 (50), 120 (100), 91 (80), 77 (60). Anal. Calcd. for C39H26N10O3 (682.22): C, 68.61; H, 3.84; N, 20.52. Found: C, 68.49; H, 3.68; N, 20.49%.
5-Oxo-V3-phenyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-chlorop-henyl)-1,5-dihydropyrido[2,3-rf][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (8k)
Yellow crystals, mp 166-168 °C; IR (KBr) u 3382 (NH), 1693, 1684, 1652 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) 86.69 (s, 1H, pyrimidine-H), 7.36-8.35 (m, 15H, Ar-H), 7.90 (d, J = 8 Hz, 2H, Ar-H), 8.45 (d, J = 8 Hz, 2H, Ar-H), 8.52 (d, J = 5 Hz, 1H, pyridine-H), 8.65 (d, J = 5 Hz, 1H, pyridine-H), 11.15 (s, 1H, NH) ppm; MS, m/z (relative intensity) 704 (M+ +2, 10), 702 (M+, 25), 582 (20), 120 (40), 111 (40), 91 (60), 77 (100). Anal. Calcd. for C38H23ClN10O3 (702.16): C, 64.91; H, 3.30; N, 19.92. Found: C, 64.79; H, 3.38; N, 20.09%.
5-Oxo-V3-phenyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-1-(4-nitrop-henyl)-1,5-dihydropyrido[2,3-rf][1,2,4]triazolo[4,3-a]pyrimidine-3-carboxamide (8l)
Yellow crystals, mp >300 °C; IR (KBr) u 3381 (NH), 1696, 1689, 1657 (3 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) 86.69 (s, 1H, pyrimidine-H), 7.41-8.45 (m, 15H, Ar-H), 8.43 (d, J = 8 Hz, 2H, Ar-H), 8.49 (d, J = 8 Hz, 2H, Ar-H), 8.58 (d, J = 5 Hz, 1H, pyridine-H), 8.69 (d, J = 5 Hz, 1H, pyridine-H), 11.19 (s, 1H, NH) ppm; MS, m/z (relative intensity) 713 (M+, 25), 593 (20), 122 (40), 91 (60), 77 (100). Anal. Calcd. for C38H23N11O5 (713.19): C, 63.95; H, 3.25; N, 21.59. Found: C, 63.781; H, 3.18; N, 21.49%.
Alternative synthesis of 3-acetyl-6-[(1,7-diphenyl-1,5-dihydro-5-oxo- [1,2,4]triazolo[4,3-a]pyrimidin-3-yl)]-1-phenyl-1,5-dihydropyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-one (8a)
A mixture of 7-amino-1,3-diphenyl[1,2,4]triazo-lo[4,3-a]pyrimidin-5(1H)-one (10)20 (0.30 g, 1 mmol) and enaminone (1) (0.22 g, 1 mmol) in acetic acid was reflu-xed for 6 hours. After cooling, the mixture was poured into ice and the solid product was filtered off and recrystal-lized from dioxane to give product identical with 8a (mp, mixed mp, IR).
Reaction of 5-[(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4] triazolo[4,3-a]pyrimidin-3-yl)]-2-thioxo-2,3-dihydro-1_ff-pyrido[2,3-d]pyrimidin-4-one (3) with 3-chloro-2,4-pentanedione (12)
To a stirred solution of 3 (0.47 g, 1 mmol) in absolute ethanol (20 mL) was added triethylamine (0.2 mL), and the mixture was warmed for 10 min at 60 °C and cooled. To the resulting clear solution was added 3-chloro-2,4-pentanedione (12) (1 mmol) dropwise while stirring the reaction mixture. After complete addition, the reaction mixture was stirred overnight at room temperature. The solid that precipitated was filtered off, washed with water, dried and finally crystallized from ethanol to give 3-[4-oxo-5-(1,7-diphenyl-1,5-dihydro-5-oxo-[1,2,4]triazo-lo [4,3-a]pyrimidin-3-yl)-3,4-dihydropyrido[2,3-d]pyri-midin-2-yl]sulfanyl-2,4-pentanedione (13) as yellow crystals, mp >300 °C; IR (KBr) u 3225 (NH), 1710, 1700, 1692, 1685 (4 CO), cm-1; 1H NMR (300 MHz, DMSO-d6) ¿2.39 (s, 3H, COCH3), 2.45 (s, 3H, COCH3), 4.95 (s, 1H, CH), 6.35 (s, 1H, pyrimidine-H), 7.12-8.06 (m, 10H, Ar-H), 8.58 (d, 1H, J = 4.5 Hz, pyridine-H), 8.69 (d, 1H, J = 4.5 Hz, pyridine-H), 11.57 (s, 1H, NH) ppm; MS, m/z (relative intensity) 563 (M+, 40), 520 (70), 464 (60), 432 (50), 131 (40), 99 (60), 77 (100). Anal. Calcd. for C29H21N7O4S (563.13): C, 61.80; H, 3.76; N, 17.40; S, 5.(59. Found: C, 61.71; H, 3.58; N, 17.29; S, 5.52%.
Alternative synthesis of 8a via coupling of 13 with ben-zenediazonium chloride
To a solution of 13 (1 mmol) in ethanol (20 mL) was added sodium acetate trihydrate (0.14 g, 1 mmol), and the mixture was cooled to 0-5 °C in an ice bath. To the resulting cold solution was added portionwise a cold solution of benzenediazonium chloride [prepared by diazotizing aniline (1 mmol) dissolved in hydrochloric acid (6 M, 1 mL) with a solution of sodium nitrite (0.07 g, 1 mmol) in water (2 mL)]. After complete addition of the diazonium salt, the reaction mixture was stirred for a further 30 min in an ice bath. The solid precipitated was filtered off, washed with water, dried and crystallized from dioxane to give the respective product identical in all respects (mp, mixed mp, IR) with 8a.
6. References
1.	H. N. Hafez, A. B. A. El-Gazzar, Bioorg. Med. Chem. Lett. 2009, 19, 4143-4147.
2.	P. Baraldi, C. Gioanni, B. Cacciari, R. Romagnoli, G. Spallu-to, K. Varani, S. Gessi, S. Merighi, P. Borea, Drug. Dev. Rev. 2001, 52, 406-411.
3.	A. B. A. El-Gazzar, H. N. Hafez, Acta Chim. Solv. 2008, 55, 359-371.
4.	A. A. Deshmukh, M. K. Mody, T. Ramalingam, P. B. Sattur, Indian J. Chem. 1984, 23B, 793-795.
5.	B. Loev, J. H. Musser, R. E. Brown, H. Jones, R. Kahen, F. C. Huang, A. Khandwala, P. Sonnino-Goldman, M. J. Leibo-witz, J. Med. Chem. 1985, 28, 363-366.
6.	R. Gupta, A. K. Gupta, S. Paul, P. L. Kachroo, Indian J. Chem. 1998, 37B, 1211-1213.
7.	S. Salameh, M. Abul-Haj, M. Quiro's, J. M. Salas, Inorg. Chim. Acta 2005, 358, 824-827.
8.	J. S. Debenham, C. B. Madsen-Duggan, J. Wanga, X. Tong, J. Lao, T. M. Fong, M. T. Schaeffer, J. C. Xiao, C. R. R. Huang, C. P. Shen, S. Stribling, L. P. Shearman, A. M. Strack, E. MacIntyre, J. J. Hale, T. F. Walsh, Bioorg. Med. Chem. Lett. 2009, 19, 2591-2594.
9.	T. A. Farghaly, S. M. Riyadh, Arkivoc 2009, (x), 54-64.
10.	S. M. Gomha, S. M. Riyadh, Arkivoc 2009, (xi), 58-68.
11.	A. S. Shawali, T. A. Farghaly, Tetrahedron 2009, 65, 644-647.
12.	T. A. Farghaly, Z. A. Abdallah, Arkivoc, 2008, (xvii), 295306.
13.	S. M. Riyadh, T. A. Farghaly, M. A. Abdallah, M. M. Abdalla, M. R. Abd El-Aziz, Eur. J. Med. Chem. 2010, 45, 1042-1050.
14.	A. S. Shawali, M. A. N. Mosselhi, F. M. A. Eltalbawy, T. A. Farghaly, N. M. Tawfik, Tetrahedron 2008, 64, 5524-5530.
15.	A. S. Shawali, T. A. Farghaly, Arkivoc 2008, (i), 18-64.
16.	T. A. Farghaly, J. Chem. Res. 2008, 152-155.
17.	E. C. Taylor, C. C. Cheng, J. Org. Chem. 1960, 25, 148-149.
18.	A. J. Elliott, P. D. Callaghan, M. S. Gibson, S. T. Nemeth, Can. J. Chem. 1975, 53, 1484-1490.
19.	K. Ishii, M. Hatanaka, I. Ueda, Chem. Pharm. Bull. 1991, 39, 3331-3334.
20.	M. A. N. Mosselhi, Monatsh. Chem. 2002, 133, 1297-1304.
21.	R. R. Phillip, Org. Reactions 1959, 10, 143-178.
22.	Suzuki, M.; Nagawa, M. J. Pharm. Soc. Jpn., 1955, 75, 394.
23.	M. O. Lozinskii, S. N. Kukoka, P. S. Pel'kis, Ukr. Khim. Zh. 1967, 33, 1295-1300. Chem. Abst. 1968, 69, 51762g.
24.	A. J. Hodgkinson, B. Staskan, J. Org. Chem. 1969, 34, 1709-1713.
25.	R. J. Grawer, J. B. Harborne, Phytochemistry 1994, 37, 19-25.
26.	O. N. Irob, M. Noo-Young, W. A. Anderson, Int. J. Pharm. 1996, 34, 87-91.
27.	N. F. Eweiss, A. Osman, J. Heterocycl. Chem. 1980, 17, 1713-1717.
28.	A. S. Shawali, A. Osman, Tetrahedron 1971, 27, 2517-2528.
29.	A. S. Shawali, N. F. Eweiss, H. M. Hassaneen, M. S. Algha-rib, Bull. Chem. Soc. Jpn. 1973, 48, 365-371.
30.	M. W. Moon, J. Org. Chem. 1972, 37, 386-390.
31.	C. Bullow, E. King, Ann. 1924, 439, 211-220.
32.	A. S. Shawali, A. O. Abdelhamid, Bull. Chem. Soc. Jpn.
33. C. Parkanyi, A. S. Shawali, J. Heterocycl. Chem. 1980, 17, 897-903.
1976, 49, 321-324.
Povzetek
V prispevku je opisana priprava vrste pirido[2,3-d][1,2,4]triazolo[4,3-a]pirimidin-5-onov (8) z reakcijo hidrazonil kloridov 5 z 5-substitukanimi-2-tiokso-2,3-dihidro-1_ff-pmdo[2,3-d]pirimidin-4-oni (3) oziroma njihovimi metiltio derivati 4. Produkti 8 so bili pripravljeni tudi po dveh alternativnih poteh; a) z reakcijo enaminona 1 in 7-amino-1,3-disubsti-tuiranega[1,2,4]triazolo[4,3-a]pirimidin-5-ona (10), oziroma b) z Japp-Klingemannovo reakcijo spojine 13. Za sintezo ciljnih spojin 8 sta bili uporabljeni tako konvencionalna tehnika kot tudi obsevanje z mikrovalovi. Narejena je primerjalna študija obeh tehnik z uporabo trietilamina oziroma citozana kot bazičnega katalizatorja. Avtorji v študiji razpravljajo o možnih mehazmih študiranih reakcij. Na novih produktih je bila preizkušena tudi antimikrobna aktivnost.