1,2,4-Oxadiazole as a potential scaffold in agrochemistry: a review

N,O-containing heterocycles have been incorporated into various approved pesticides and pesticide candidates. The persistent challenge in contemporary crop protection lies in the continuous pursuit of novel N,O-heterocycle-containing compounds with pesticidal properties. Among them, the 1,2,4-oxadiazole scaffold is one of the most extensively explored heterocycles in new pesticide discovery and development. This review focuses on elucidating the molecular design strategy employed along with highlighting the bioactivity of 1,2,4-oxadiazole derivatives since 2012. Throughout this time frame, tioxazafen and flufenoxadiazam have emerged as prominent examples in which 1,2,4-oxadiazole derivatives were utilized as the core active structure within numerous applications. Additionally, the preparation methods for substituted 1,2,4-oxadiazole derivatives are elaborated upon, and their potential value within agrochemistry is discussed.

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.

PdII on Guanidine-Functionalized Fe3O4 Nanoparticles as an Efficient Heterogeneous Catalyst for Suzuki-Miyaura Cross-Coupling and Reduction of Nitroarenes in Aqueous Media

This paper presents guanidine-functionalized Fe3O4 magnetic nanoparticle-supported palladium (II) (Fe3O4@Guanidine-Pd) as an effective catalyst for Suzuki-Miyaura cross-coupling of aryl halides using phenylboronic acids and also for selective reduction of nitroarenes to their corresponding amines. Fe3O4@Guanidine-Pd synthesized is well characterized using FT-IR spectroscopy, XRD, SEM, TEM, EDX, thermal gravimetric analysis, XPS, inductively coupled plasma-optical emission spectroscopy, and vibrating sample magnetometry analysis. The prepared Fe3O4@Guanidine-Pd showed effective catalytic performance in the Suzuki-Miyaura coupling reactions by converting aryl halides to their corresponding biaryl derivatives in an aqueous environment in a shorter reaction time and with a meagerly small amount of catalyst (0.22 mol %). Also, the prepared Fe3O4@Guanidine-Pd effectively reduced nitroarenes to their corresponding amino derivatives in aqueous media at room temperature with a high turnover number and turnover frequency with the least amount of catalyst (0.13 mol %). The most prominent feature of Fe3O4@Guanidine-Pd as a catalyst is the ease of separation of the catalyst from the reaction mixture after the reaction with the help of an external magnet with good recovery yield and also reuse of the recovered catalyst for a few cycles without significant loss in its catalytic activity.

Novel 1,2,4-Oxadiazole Derivatives in Drug Discovery

Five-membered 1,2,4-oxadiazole heterocyclic ring has received considerable attentionbecause of its unique bioisosteric properties and an unusually wide spectrum of biological activities.Thus, it is a perfect framework for the novel drug development. After a century since the1,2,4-oxadiazole have been discovered, the uncommon potential attracted medicinal chemists'attention, leading to the discovery of a few presently accessible drugs containing 1,2,4-oxadiazoleunit. It is worth noting that the interest in a 1,2,4-oxadiazoles' biological application has been doubledin the last fifteen years. Herein, after a concise historical introduction, we present a comprehensiveoverview of the recent achievements in the synthesis of 1,2,4-oxadiazole-based compounds and themajor advances in their biological applications in the period of the last five years as well as briefremarks on prospects for further development.