In this project, a 1,2,4-triazole and eight 1,2,4-triazole-1,3,4-thiadiazole derivatives were successfully synthesized and characterized. On the other hand, 1,2,4-triazole-1,3,4-thiadiazoles were synthesized by refluxing 1,2,4-triazole and benzoic acid derivatives in the presence of phosphorus oxychloride as the cyclizing agent. The structure of 1,2,4-triazole and 1,2,4-triazole-1,3,4-thiadiazole derivatives (XT1-XT8) were characterized by FT-IR, 1H NMR, 13C NMR, DEPT, HMQC and HMBC spectroscopies as well as melting point apparatus.
The percentage yield of 1,2,4-triazole obtained was 31 %, while XT1-XT8 were synthesized with the percentage yield in the range of 8 – 69. Structure 1,2,4-triazole and derivative 1,2,4- triazolo -1,3,4-thiadiazole (XT1-XT8) shows a large number of spectra from FT-IR, 1H NMR, 13C NMR, DEPT, HMQC and HMBC. I hereby declare that this final year project report is based on my original work except for quotations and citations duly acknowledged.
It is certified that LOO XIN TONG (ID No: 19ADB02955) has completed this final year project report entitled "SYNTHESIS AND CHARACTERIZATION OF 1,2,4-TRIAZOLO-1,3,4-THIADIAZOLES" under the supervision of ASSOCIATE. 23 3.3 List of chemicals used in thin layer chromatography (TLC) 24 3.4 List of chemicals used in nuclear magnetic resonance.
Triazole
New triazole drugs have been discovered and developed using the bioisosteric substitution technique. Since then, they have attracted attention for medicinal chemistry research due to their prominent biological activities that have been discovered (Kumari et al., 2021). The technique addresses these limitations while still maintaining the strength of the lead compound.
When bioisosteres are used and structural changes are introduced to the lead compound, changes can be made. The lone pairs of electrons from the two pyridine-like nitrogen atoms in the triazole behave as hydrogen bond acceptors, mimicking the role of the oxygen atom in the amide. On the other hand, the strong dipole moment exhibited by the CH bond of triazole allows it to act as a hydrogen bond donor comparable to the NH bond of an amide.
These properties allow the initiation of hydrogen bonds by the triazole, followed by participation in π-interactions (Sainas and Lolli, 2021). Some marketed medicines that contain triazole moiety include anastrazole, lithazole, vorozole, fluconazole, itraconazole, myclobutanil, paclobutrazole, posaconazole, tebuconazole, rizatriptan and ribavirin (Kumari et al., 2021). Among the two isomeric forms of triazole which are 1,2,3-triazole and 1,2,4-triazole, substitution can be done at positions three, four and five of triazole ring, but it is found that the groups attached to the nitrogen attached is atom at the fourth position contributes to the greatest change in physico-chemical and biological properties.
1,2,4-triazole has received the attention of researchers due to its ability in terms of biological activities such as anticancer, anticonvulsant, antiinflammatory, antimicrobial, antimigraine, antioxidant, antiparasitic, antiurease, and antiviral (Kumari et al., 2021). One of the substituted 1,2,4-triazoles is 3-mercapto-1,2,4-triazole, which is studied in this project. There are two tautomeric forms for this compound, which are shown in Figure 1.3.
The thion form has the mobile hydrogen attached to the nitrogen, while for the thiol form, the sulfur has the attachment of the mobile hydrogen, where the thion form predominates (Shneine and Alaraji, 2016).
Thiadiazole
Some marketed drugs containing a thiadiazole moiety include acetazolamide, cefazolin, methazol amide, megazole, and sulfamethizole (Babalouei and Tahghighi, 2017). The chemistry of 1,3,4-thiadiazole was developed after the discovery and discovery of hydrazine and phenylhydrazines in the late 19th century. 1,3,4-thiadiazoles are widely used in agriculture, including bactericides, fungicides, insecticides, herbicides, and pesticides (Yakan, 2020).
Compounds bearing this thiadiazole group are reported to have the potential of antibacterial, analgesic, anticonvulsant, antifungal, antileishmanial, anti-inflammatory, antidepressant, antipsychotic, antituberculosis and anticancer agents, in particular. The heterocyclic ring of 1,3,4-thiadiazole is a bioisostere of a pyrimidine, which is the backbone of the structures of three nucleobases of DNA. As a result, 1,3,4-thiadiazole molecules that are cytostatically active can interfere with DNA synthesis and subsequently hinder the replication of human tumor and bacterial cells.
Synthesis with bond formation is accomplished via the ring-closing reaction of an acylated thiosemicarbazide, as shown in Figure 1.5. On the other hand, synthesis with the formation of two bonds is carried out via 1,3-dipolar cycloaddition as shown in Figure 1.6. 12 In addition, 1,3,4-thiadiazoles can also be synthesized by refluxing 1,3,4-oxadiazoles in ethanolic hydrochloric acid as shown in Figure 1.8 (Othman, Kihel, and Amara, 2019).
Objectives
Synthesis of 1,2,4-triazole
The 5-substituted 4-amino-3-mercapto-1,2,4-triazole was synthesized through the cyclocondensation of thiocarbohydrazide with various carboxylic acids, including acetic acid, butyric acid, formic acid, and propionic acid. In addition, 1,2,4-triazole is also reported to be synthesized by a one-pot reaction by heating potassium dithiocarbazinate, hydrazine hydrate, and water under reflux. In this study, 0.1 mol of potassium dithiocarbazine, 0.3 mol of hydrazine hydrate, and 5 mL of water were heated under reflux for 8 h.
The reaction mixture was then diluted with 5 mL of cold water, before being acidified with dilute hydrochloric acid to give a white precipitate.
Synthesis of 1,3,4-thiadiazole
The reaction is shown in Figure 2.3. 16 According to Janowski et al, thiadiazoles were synthesized from the reaction between 1,4-disubstituted thiosemicarbazides and concentrated sulfuric acid at room temperature. The fusion of 1,2,4-triazole and 1,3,4-thiadiazole rings leads to the formation of heterocyclic compounds that have a wide range of pharmacological properties (Trafalis et al., 2021). The resulting compounds were found to exhibit a wide range of biological activities, including bactericidal, fungicidal, herbicidal, insecticidal, analgesic, anticancer, anticonvulsant, and anti-inflammatory (Lin et al., 2017).
For example, Trafalis et al. 2021) reported that 1,2,4-triazolo-1,3,4-thiadiazoles were found to have good binding to the ATP (adenosine triphosphate) binding site of Akt1 and Akt2, where Akt is known as protein kinase B with three isoforms consisting of Akt1, Akt2 and Akt3. After completion of the reaction, the mixture was allowed to cool to room temperature and then placed in ice, followed by the addition of aqueous potassium carbonate to adjust the pH to the value of eight. The drying of the organic extracts was done with sodium sulfate, followed by filtration.
18 On the other hand, Baburajeev et al. 2017) reported the synthesis of 1,2,4-triazolo-1,3,4-thiadiazoles by sulfated cerium-catalyzed cyclization reaction. The removal of solvent was carried out under reduced pressure and the concentrated mass was placed in ice, followed by adjusting the pH to the value of eight using potassium carbonate and potassium hydroxide. They reported that the efficiency of the catalyst for the cyclization was improved by the modification of sulfated cerium oil with anions such as sulfate ions which led to the formation of excellent acid catalyst.
At the same time, an intermediate was formed upon attack of an electron-deficient acyl ion by a lone pair of electrons from nitrogen. After the reaction was complete, the mixture was placed in ice water, to which sodium hydroxide solution was added to adjust the pH to a value of eight. The reaction is shown in the figure, which shows the synthesis of 1,2,4-triazolo-1,3,4-thiadiazoles by condensation of equimolar 1,2,4-triazole with various substituted or unsubstituted aryl acids for 5 to 6 hours in the presence of 10 mL of phosphorus oxychloride.
The reaction mixture was then stirred in ice-cold water for 4 to 5 hours before being left overnight.
List of chemicals
List of equipment
Fourier-Transform Infrared (FT-IR) Spectroscopy
During the absorption process, the absorbed frequencies of the infrared radiation will match the natural vibrational frequencies of the sample molecule. The amplitude of the vibrational movements of the bonds in the molecule is increased by the absorbed energy. Then the die insert was inserted into the carrier plate and placed on the lower die.
After the upper die was connected, the assembly was inserted into the press to press the sample into a pellet. Upon completion of the press, the upper die and lower die were removed and the sample pellet was retrieved. The pellet was then inserted into the instrument for analysis which produced the IR spectrum.
NMR works on the principle of the spin property of the nucleus of an atom, where the magnetic field is created by a rotating charge. This makes it possible to determine the chemical environment in the immediate vicinity of a particular hydrogen atom, such as nearby double bonds and atoms and bond types. During the analysis, some nuclei in the aligned state are excited to the opposite state by the impact of a strong pulse of radio frequency energy.
When the nuclei relax to the aligned state, they release radio frequency energy at the exact resonance frequency of the relaxing nucleus. This leads to the NMR spectrum which is a graph of frequency versus intensity that depicts the different frequencies as peaks in the graph (Jacobsen, 2017). 28 In the laboratory, 10 mg of sample was dissolved by deuterated chloroform and dimethyl sulfoxide solvent in a sample vial.
Deuterated chloroform was used as the solvent to prevent the appearance of interfering signals from protons present in the solvent itself.
Conclusion
Since studies have reported that 1,2,4-triazolo-1,3,4-thiadiazoles exhibit strong pharmacological properties, further studies can be done on the properties such as antibacterial, anticancer, antimicrobial, antimigraine and antioxidant activities. Moreover, 1,2,4-triazolo-1,3,4-thiadiazoles can also be synthesized with certain structural modifications using benzoic acids with different substituents. Furthermore, green synthesis of 1,2,4-triazolo-1,3,4-thiadiazoles can be studied where more green methods can be utilized during the synthesis such as the use of microwave radiation to increase the energy efficiency of the reaction.
Identification of a new class of triazolothiadiazoles as potent inhibitors of human heparanase and their anticancer activity. Synthesis under microwave irradiation of [1,2,4]Triazolo[3,4-b][1,3,4]thiadiazoles and other diazoles containing indole moieties and their antimicrobial evaluation. Synthesis, urease inhibition, antioxidant and antibacterial studies of some 4-amino-5-aryl-3H-1,2,4-triazol-3-thiones and their 3,2,4-triazolo[3,4 6- substituted -b] 1,3,4-thiadiazole derivatives.
Novel triazolothiadiazole and triazolothiadiazine derivatives as Eg5 and HIV kinesin inhibitors: synthesis, QSAR and modeling studies. Synthesis and Characterization of New Series of 1,2,4-Triazolo[3,4-b]-1,3,4-Thiadiazole Derivatives of Anilinoacetic Acids as Promising Antioxidant Agents.
