New functionalized fused heterocycles, such as, 1,3,6,9,11-pentasubstituted-pyrido[3,2- f:6,5- f']bis([1,2,4]triazolo[4,3- a]-pyrimidin-5(1 H)-ones (6) and 1,3-disubstituted-7-[( E)-2-(thiophen-2-yl)ethenyl]-1,4,9,9a-tetrahydro-6 H-[1,2,4]triazino[4,3- b][1,2,4,5]-tetrazin-6-ones (16) were synthesized via reaction of the hydrazonoyl chlorides (1) with 1,3,6-triphenyl-9-thioxo-9,10-dihydro-pyrimido [4,5- b]pyrido[4,5- d][1,2,4]triazolo[4,3- a]pyrimidin-5,7(1 H,8 H)-di-one (5) and 4-amino-6-[(2-thiophen-2-yl)ethenyl]-3-thioxo-3,4-dihydro-[1,2,4]triazin-5(2 H)-one (11), respectively. The mechanism and the regioselectivity of the studied reactions have been discussed. The biological activity of the products has been evaluated against some fungi and bacteria species. The tested compounds exhibited moderate activity against the bacteria species.
The interest in the chemistry of hydrazonoyl halides is a consequence of the fact that they undergo a wide variety of reactions which provide routes to a number of both heterocyclic and acyclic compounds [
Some fused heterocycles showed antibacterial, antifungal [
All melting points were measured on an electrothermal melting point apparatus and are uncorrected. The 1H and 13C NMR spectra were recorded in deuterated dimethyl sulphoxide (DMSO-d6) at 300 MHz on a Varian Mercury VXR-300 NMR spectrometer (Cairo University, Egypt). 600 MHz Bruker NMR spectrometer (King Abdelaziz University, Saudi Arabia) and chemical shifts were related to that of the solvent. The infrared spectra were recorded in potassium bromide discs on a Pye-Unicam, SP300 and Shimadzu, FT IR 8101 PC infrared spectrophotometers.
Biological activity was carried out at the Microanalytical Center of Cairo University, Cairo, Egypt. Mass spectra were recorded on a Shimadzu GC MS-QP 1000 EX mass spectrometer at 70 e.V. Elemental analyses were carried out at the Microanalytical Center of Cairo University, Cairo, Egypt. The starting compounds, N-phenyl benzenecarbohydrazonoylchloride (1a) [
Reaction of N-Phenyl benzenecarbohydrazonoyl chloride (1a) with 6- aminouracil-2-thione (2): Synthesis of 7-amino-1,3-diphenyl [1,2,4]triazolo [4,3-a]pyrimidin-5(1H)-one (3) [
To a mixture of 6-aminouracil-2-thione (2) [
Reaction of 7-Amino-1,3-diphenyl[1,2,4]triazolo[4,3-a]pyrimidin-5(1H)- one (3) with benzaldehyde and ethyl cyanoacetate: Synthesis of 8-amino- 1,3,6-triphenyl-7-ethoxycarbonyl-pyrido[2,3-f][1,2,4]triazolo[4,3-a]pyrimidin-5 (1H)-one (4).
7-Amino-1,3-diphenyl[1,2,4]triazolo[4,3-a]pyrimidin-5(1H)-one (3) (2 g, 6.6 mmol) was dissolved in 40 ml of dimethylformamide. To this solution, 0.8 ml (6.6 mmol) benzaldehyde and then 0.8 ml (6.6 mmol) ethyl cyanoacetate were added. The mixture was refluxed for 6 h. After cooling, the solvent was evaporated and 20 ml H2O cold was added. The solid formed was filtered, washed with cold H2O and then crystallized from ethanol:dioxane (v/v, 9:1) to give 4.
Yield: 3.3 g (99.69%); m.p. 297˚C - 300˚C; IR (KBr):
Reaction of 4 with potassium thiocyanate: Synthesis of 1,3,6-triph- enyl-9-thioxo-9,10-dihydropyrimido[4,5-b]pyrido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidin-5,7(1H,8H)-dione (5).
To a solution of 4 (1 g, 1.99 mmol) and dioxane in acetic acid (20 ml) and drops 10% HCl, potassium thiocyanate (0.1 g, 1.03 mmol) was added and the mixture was refluxed for 7 h. After cooling, the solvent was evaporated and 20 ml H2O was added. The solid formed was filtered, washed with H2O and crystallized from ethanol and drops of dioxane to give 5 as pale yellow crystals.
Yield: 0.9 g (87.73%); m.p. 270˚C; IR (KBr):
Reaction of 5 with hydrazonoyl chlorides, (N-phenyl benzenecarbohydrazonoyl chloride(1a) & N-Phenyl-2-Phenylamino-2-oxoethanehydrazo- noyl chloride (1b)): Synthesis of 1,3,6,9,11-pentasubstituted-pyrido[3,2- f:6,5-f']bis([1,2,4]triazolo[4,3-a]-pyrimidin-5(1H)-ones (6).
General procedure:
Toa mixture of 1,3,6-triphenyl-9-thioxo-9,10-dihydropyrimido[4,5-b]pyrido [4,5-d][1,2,4]triazolo[4,3-a]pyrimidine-5,7(1H,8H)-dione (5) (0.5 g, 1 mmol) and the appropriate hydrazonoyl chloride 1a or 1b (1 mmol) in 15 ml dioxane and triethylamine (0.15 ml, 1 mmol) were added. The reaction mixture was heated under reflux until the evolution of hydrogen sulfide gas had ceased, for (24 h) (as evidenced by TLC). The reaction mixture, on cooling, afforded only one product in each case (TLC) and then the solvent was distilled off, and the residue was cooled. The solid formed was filtered, washed with H2O, and crystallized from ethanol: dioxane (v/v, 9:1) to give 6.
1,3,6,9,11-pentaphenylpyrido[3,2-f:6,5-f']bis([1,2,4]triazolo[4,3-a]-pyrimidin-5(1H)-ones (6a).
Yield: 0.2 g (30.52%);Yellow crystals; m.p. 294˚C; IR (KBr):
1,3,6,11-tetraphenyl-9-phenylaminocarbonylpyrido[3,2-f:6,5-f']di([1,2,4] triazolo[4,3-a]-pyrimidin-5(1H)-ones (6b).
Yield: 0.2 g (28.69%); Yellow solid; m.p. 272˚C - 273˚C; IR (KBr):
Reaction of hydrazonoyl chlorides (1a-d) with 4-amino-6-[(2-thiophen-2- yl)ethenyl]-3-thioxo-3,4-dihydro-[1,2,4]triazin-5(2H)-one (11).
General procedure:
To a mixture of 4-amino-6-[(2-thiophen-2-yl)ethenyl]-3-thioxo-3,4-dihydro- [1,2,4]triazin-5(2H)-one (11) (2 mmol) [
16a: 1,3-diphenyl-7-[(E)-2-(thiophen-2-yl)ethenyl]-1,4,9,9a-tetrahydro- 6H-[1,2,4]triazino[4,3-b][1,2,4,5]tetrazin-6-one.
Yield: 0.2 g, 24.39%; yellow solid; m.p. 174˚C; IR (KBr)
16b: 3-Phenylamido-1-phenyl-7-[(E)-2-(thiophen-2-yl)ethenyl]-1,4,9,9a- tetrahydro-6H-[1,2,4]triazino[4,3-b][1,2,4,5]tetrazin-6-one.
Yield: 0.2 g, 22. 15%; yellow solid; m.p. 211˚C - 214˚C; IR (KBr)
16c: 3-Acetyl-1-phenyl-7-[(E)-2-(thiophen-2-yl)ethenyl]-1,4,9,9a-tetra- hydro-6H-[1,2,4]triazino[4,3-b][1,2,4,5]tetrazin-6-one.
Yield: 0.1 g, 13.33%; pale yellow solid; m.p. 105˚C; IR (KBr)
16d: Ethyloxo-1-phenyl-7-[(E)-2-(thiophen-2-yl)ethenyl]-1,6,9,9a-tetra- hydro-4H-[1,2,4]triazino[4,3-b][1,2,4,5]tetrazin-3-carboxylate.
Yield: 0.2 g, 24.69%; orange solid; m.p. 1118˚C; IR (KBr)
Cultures of two bacterial species namely, Escherichia coli EC, and Staphylococcus aureus SA as well as well as two fungal species, namely Aspergillus flavus AF, and Candida albicans CA were used to investigate the antimicrobial activity of eight products, namely 4, 5, 6a, 6b and 16a-16d. The antimicrobial activity tests were carried out in the Microbiology Division of Microanalytical Center of Cairo university using the diffusion plate technique [
The first required starting material in this part, 7-amino-1,3-diphenyl[1,2,4] triazolo[4,3-a]pyrimidin-5(1H)-one (3) [
(4). The latter compound was cyclized by refluxing in a mixture of potassium thiocyanate and dioxane in the presence of concentrated hydrochloric acid affording1,3,6-triphenyl-9-thioxo-9,10-dihydropyrimido[4,5-b]-pyrido[4,5-d][1,2, 4]triazolo[4,3-a]pyrimidin-5,7(1H,8H)-dione (5) (Scheme 1).
The 1H NMR spectrum of each of the resulting products 4 and 5 is in agreement with the given structure [see experimental part]. Hence, the product 4 revealed characteristic signals for ethyl ester and amino groups at d = 1.25 (t, 3H, CH3), 4.31 (q, J = 7.3, 2H, CH2), 6.75 (s, 2H. NH2, D2O exchangeable), while the product 5 revealed characteristic signals of new 2 NH at d = 9.45 (s, 1H, NH, D2O exchangeable) and 11.19 (s, 1H, NH, D2O exchangeable). Reaction of
Scheme 1. Reaction of hydrazonoyl chloride with 1,3,6-triphenyl-9,10-dihydropyrimido [4,5-b]pyrido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidin-5,7[1H,i8iH]-dione(5).
1,3,6-triphenyl-9-thioxo-9,10-dihydropyrimido[4,5-b]pyrido[4,5-d][1,2,4]triazolo[4,3-a]pyrimi-din-5,7(1H,8H)-dione (5) with hydrazonoyl chlorides 1a,b were carried out in dioxane in the presence of triethylamine at reflux until the evolution of hydrogen sulfide gas had ceased. The reaction mixture, on cooling, afforded only one product in each case (as evidenced by TLC). Both spectroscopic data and elemental analyses were consistent with structure 6 or 7 (Scheme 1). An immediate distinction between these two structures was reached by comparison of the 13C NMR spectra with those of similar annulated pyrimidinones. Literature report [
The chemical shift values of the annelatedpyrimidinones A and B are shown in Chart 1 [
On the basis of this similarity, the isolated products were assigned structure 6 and the isomeric structure 7 was excluded. As depicted in Scheme 1. The reaction proceeded through S-alkylation [
Also the reaction of 6-aminouracil-2-thione (2) with benzaldehyde in acetic acid afforded the compound 10 [
Our study was extended to introduce 1,2,4-triazine containing thiophene moiety which has wide applications in different biological and medicinal fields beside its application in organic chemistry [
Chart 1. 13C NMR Shifts of strategic carbon atoms.
Scheme 2. Mechanism of the formation of 1,3,6,9,11,-pentasubstitited-pyrido [3,2-f:6,5-f] di([1,2,4])trizaolo[4,3-a]pyrimidin-5(1H)-one (6).
Scheme 3. Alternate Synthesis of 1,3,6,9,11-pentasubstituted-pyrido [3,2-f:6,5-f]di ([1,2,4])trizaolo[4,3-a]pyrimidin-5(1H)-one (6).
3,4- dihydro-[1,2,4]triazin-5(2H)-one (11) [
It was initially anticipated that such reactions would yield the respective 1,2,4- triazino[2,1-b][1,3,4,5]thiatriazine (13) by analogy to the reactions of 1a-d with 2-aminothiophenol, which were reported to afford benzothiadiazine derivatives [
Scheme 4. reaction of 4-amino-6-[2-(thiophen-2-yl) ethenyl]-3-thioxo-3,4-dihydro- 1,2,4-triazin-5(2H)-one(11) with Hydrazonoyl Chlorides 1a-d.
were identified as 1,3-disubstituted-7-[(E)-2-(thiophen-2-yl)ethenyl]-1,4,9,9a- tetrahydro-6H-[1,2,4]triazino[4,3-b][1,2,4,5]-tetrazin-6-one (16) and not 13. The structures of the latter products were elucidated on the basis of their spectra (1H & 13C NMR, IR, and MS) and microanalyses. For example, the 1HNMR spectra of the product 16a showed NH proton signal at d 8.8, and it was lacking the N-NH2 signal at d 6.5, which is characteristic of the starting substrate 11. The mass spectra of 16a were also consistent with its assigned structures, especially its molecular ion peak. The formation of 16a-d from 1a-d and 11 can be rationalized in terms of the pathway outlined in Scheme 4. It is suggested that the reaction begins with the formation of the respective hydrazide 14, that cyclized to 15, which in turn give 16 with concurrent elimination of hydrogen sulfide (Scheme 4) [
The test results revealed that all compounds exhibited moderate activity against the two bacterial species except, 5, 6b and all compounds showed no activity against all fungal species, except compounds 5, and 16c against Candida albicans (CA) (
Compound No. | (EC) G− | (SA) G+ | (AF) Fungus | (CA) Fungus |
---|---|---|---|---|
Control: DMSO | 0.0 | 0.0 | 0.0 | 0.0 |
Ampicillin Antibacterial agent | 22+++ | 18+++ | − | − |
Amphotericin B Antifungal agent | − | − | 17++ | 19++ |
4 | 11++ | 12++ | 0.0− | 0.0− |
5 | 9+ | 10++ | 0.0− | 10++ |
6a | 0.0− | 0.0− | 0.0− | 0.0− |
6b | 0.0− | 0.0− | 0.0− | 0.0− |
16a | 9+ | 9+ | 0.0− | 0.0− |
16b | 17++ | 20+++ | 0.0− | 0.0− |
16c | 11++ | 11++ | 0.0− | 11++ |
16d | 15++ | 14+++ | 0.0− | 0.0− |
*IZD = 2 - 10 mm beyond control = + (low activity). IZD = 11 - 24 mm beyond control = ++ (moderate activity). IZD = 25 - 35 mm beyond control = +++ (high activity).
In this report, it is found that hydrazonoyl chlorides (1) are good precursor to synthesize fused heterocycles. Thus the reaction of such hydrazonoyl chlorides (1) with 1,3,6-triphenyl-9-thioxo-9,10-dihydropyrimido[4,5-b]pyrido[4,5-d][1,2,4]triazolo[4,3-a]pyrimidin-5,7(1H,8H)-dione (5) and 4-amino-6-[(2-thiophen-2-yl) ethenyl]-3-thioxo-3,4-dihydro-[1,2,4]triazin-5(2H)-one (11) afforded to new functionalized fused heterocycles. Spectral data revealed that such fused heterocycles have the structures of 1,3,6,9,11-penta-substitutedpyrido[3,2-f:6,5-f']bis- ([1,2,4]triazolo[4,3-a]-pyrimidin-5(1H)-ones (6) and 1,3-disubstituted-7-[(E)-2- (thiophen-2-yl)ethenyl]-1,4,9,9a-tetrahydro-6H-[1,2,4]triazino[4,3-b][1,2,4,5]- tetrazin-6-ones (16) respectively. The antibacterial and antifungal activity screening of the prepared compounds revealed moderate activity against the bacterial species.
The authors thank King Abdulaziz City for Science and Technology (KACST), Kingdom of Saudi Arabia (KSA) for the financial support under project number AT36-062. This paper is dedicated to the memory of Prof. Dr. Dr. Ahmad Sami Abdelshakour Shawali, Cairo University, Egypt.
Mohamed, M.A.M., Abu-Alola, L.M.B., Al-Zaidi, O.N.A. and Saad, H.A.H. (2017) Cyclocondensation Re- actions of Hydrazonoyl Chlorides with Some Azines: Synthesis of New Fused Heterocycles of Expected Microbiological Activity. International Journal of Organic Chemistry, 7, 12-24. http://dx.doi.org/10.4236/ijoc.2017.71002