Manganese oxide nanoparticles supported on graphene oxide as an efficient nanocatalyst for the synthesis of 1,2,4‐oxadiazoles from aldehydes

Thiol-promoted intermolecular cyclization to synthesize 1,2,4-oxadiazoles including tioxazafen under transition metal-free conditions

A simple and efficient one-pot intermolecular annulation reaction for the synthesis of 1,2,4-oxadiazoles from amidoximes and benzyl thiols has been developed, in which benzyl thiols act as not only reactants but also organo-catalysts. The control experiments proved that thiol substrates could facilitate the dehydroaromatization step. High yield, functional group diversity and transition metal-free, extra oxidant-free, and mild conditions are the important practical features. Moreover, this protocol provides an effective alternative method for the synthesis of a commercially available broad-spectrum nematicide, tioxazafen.

A Novel Protocol for the Synthesis of 1,2,4-Oxadiazoles Active against Trypanosomatids and Drug-Resistant Leukemia Cell Lines

Cancer and parasitic diseases, such as leishmaniasis and Chagas disease, share similarities that allow the co-development of new antiproliferative agents as a strategy to quickly track the discovery of new drugs. This strategy is especially interesting regarding tropical neglected diseases, for which chemotherapeutic alternatives are extremely outdated. We designed a series of (E)-3-aryl-5-(2-aryl-vinyl)-1,2,4-oxadiazoles based on the reported antiparasitic and anticancer activities of structurally related compounds. The synthesis of such compounds led to the development of a new, fast, and efficient strategy for the construction of a 1,2,4-oxadiazole ring on a silica-supported system under microwave irradiation. One hit compound (23) was identified during the in vitro evaluation against drug-sensitive and drug-resistant chronic myeloid leukemia cell lines (EC₅₀ values ranging from 5.5 to 13.2 µM), Trypanosoma cruzi amastigotes (EC₅₀ = 2.9 µM) and Leishmania amazonensis promastigotes (EC₅₀ = 12.2 µM) and amastigotes (EC₅₀ = 13.5 µM). In silico studies indicate a correlation between the in vitro activity and the interaction with tubulin at the colchicine binding site. Furthermore, ADMET in silico predictions indicate that the compounds possess a high druggability potential due to their physicochemical, pharmacokinetic, and toxicity profiles, and for hit 23, it was identified by multiple spectroscopic approaches that this compound binds with human serum albumin (HSA) via a spontaneous ground-state association with a moderate affinity driven by entropically and enthalpically energies into subdomain IIA (site I) without significantly perturbing the secondary content of the protein.

Convenient one-pot synthesis of 1,2,4-oxadiazoles and 2,4,6-triarylpyridines using graphene oxide (GO) as a metal-free catalyst: importance of dual catalytic activity

A convenient and efficient process for the synthesis of 3,5-disubstituted 1,2,4-oxadiazoles and 2,4,6-triarylpyridines has been described using an inexpensive, environmentally benign, metal-free heterogeneous carbocatalyst, graphene oxide (GO). GO plays a dual role of an oxidizing agent and solid acid catalyst for synthesizing 1,2,4-oxadiazoles and triarylpyridines. This dual catalytic activity of GO is due to the presence of oxygenated functional groups which are distributed on the nanosheets of graphene oxide. A broad scope of substrate applicability and good sustainability is offered in this developed protocol. The results of a few control experiments reveal a plausible mechanism and the role of GO as a catalyst was confirmed by FTIR, XRD, SEM, and HR-TEM analysis.