Ultrasound-Assisted Synthesis, Antioxidant Activity and Computational Study of 1,3,4-Oxadiazol-2-amines

Abstract

Development of synthetic procedures for the preparation of 1,3,4-oxadiazole derivatives has always been in the interest of researchers as a result of their widespread biological activities. In this study, an ultrasound-assisted procedure was proposed for the synthesis of 1,3,4-oxadiazol-2-amines form the reaction of hydrazides and cyanogen bromide. They were efficiently produced in 81–93% yields in the presence of ethanol and potassium bicarbonate as the reaction media and the base, respectively. Their antioxidant properties were determined via DPPH free radical scavenging method as one of the most basic steps in identifying other related biological effects. IC50 values were in the range of from 0.237 to 0.863 mM. The synthesized 1,3,4-oxadiazoles are protective agents against oxidative stress, and can be used in the treatment of cancer, candidiasis, diabetes, neurodegenerative and inflammatory diseases. Furthermore, bond dissociation energies (BDEs) and electron densities based NCI (non-covalent interactions) were calculated using density-functional theory (DFT) to understand the observed reactivities. It was found that reversible dipole-dipole forces play a key role in most interactions.

Synthesis and Biological Activity of 1,3,4-Oxadiazoles Used in Medicine and Agriculture

“…The reaction mixture was subjected to an ultrasonic bath at 50 • C. The formed oxadiazole derivatives were washed with water and dried to give pure final products. The undoubted advantage of using ultrasonic prilling is the reduction of the synthesis time to several hours and the high yield of the desired 1,3,4-oxadiazole derivatives (40a-e) [104]. The obtained 2-amino-1,3,4-oxadiazole derivatives were tested for their antioxidant activity.…”

“…All obtained final products, except derivative 40d, showed antioxidant activity. The strongest properties were exhibited by derivative 40c; this was attributed to the presence of a nitro group, which is capable of withdrawing electrons and deactivating the phenyl ring [104].…”

“…Scheme 8. Synthesis of 2-amino-1,3,4-oxadiazole derivatives[104].The obtained 2-amino-1,3,4-oxadiazole derivatives were tested for their antioxidant activity. The tests were carried out against 2,2,-diphenyl-1-picrylhydrazyl (DPPH).…”

Ultrasound-assisted transition-metal-free catalysis: a sustainable route towards the synthesis of bioactive heterocycles

“…Treatment of various hydrazides 71 and cyanogen bromide 72 in the presence of potassium bicarbonate as an efficient catalyst in ethanol under ultrasonication at 50 °C was found to lead to a variety of 1,3,4-oxadiazole derivatives 73 in 81–93% yields after 2.5–7 hours ( Scheme 18 ). 88 Alkyl and heteroaryl substituted aldehydes situated on the hydrazide ring have been well sustained by this approach, like aromatic aldehydes with varied electron-withdrawing and electron-donating groups. The significant outcome of the present method was established by authenticating the antioxidant properties of most of the synthesized compounds.…”

Assessment of Phenolic and Flavonoid Contents, Antioxidant Properties, and Antimicrobial Activities of Stocksia Brahuica Benth

“…The DPPH free radical scavenging method was performed to assess IC 50 values (half-maximal inhibitory concentration) according to the previously published researches. [24][25][26] Briefly, solutions containing 1 mL of methanolic extracts of powdered seeds, fruits, and leaves of S. brahuica and 4 ml of newly made DPPH methanolic solution (0.004% w/v) were prepared in separate test tubes. The test tubes remained in blackness for 30 minutes at room temperature.…”