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Background: Urea, thiourea, and 1,2,4-oxadiazole compounds are of great interest due to their different activities such as anti-inflammatory, antiviral, analgesic, fungicidal, herbicidal, diuretic, antihelminthic and antitumor along with antimicrobial activities. Objective: In this work, we provide a new series of potential biologically active compounds containing both 1,2,4- oxadiazole and urea/thiourea moiety. Methods: First, 5-chloromethyl-3-aryl-1,2,4-oxadiazoles (3a-j) were synthesized from the reaction of different substituted amidoximes (2a-j) and chloroacetyl chloride in the presence of pyridine by conventional and microwave-assisted methods. In the conventional method, 1,2,4-oxadiazoles were obtained in two steps. Oacylamidoximes obtained in the first step at room temperature was heated in toluene for an average of one hour to obtain 1,2,4-oxadiazoles. The yields varied from 70 to 96 %. 1,2,4-oxadiazoles were obtained under microwave irradiation in a single step in a 90-98 % yield at 160 °C in five minutes. 5-aminomethyl-3-aryl-1,2,4-oxadiazoles (5a-j) were obtained by Gabriel amine synthesis in two step from corresponding 5-chloromethyl-3-aryl-1,2,4- oxadiazoles. Finally, twenty new urea (6a-j) and thiourea (7a-j) compounds bearing oxadiazole ring were synthesized by reacting 5-aminomethyl-3-aryl-1,2,4-oxadiazoles with phenyl isocyanate and isothiocyanate in tetrahydrofuran (THF) at room temperature with average yields (40-70 %). Results: An efficient and rapid method for the synthesis of 1,2,4-oxadiazoles from the reaction of amidoximes and acyl halides without using any coupling reagent under microwave irradiation has been developed, and twenty new urea/thiourea compounds bearing 1,2,4-oxadiazole ring have been synthesized and characterized. Conclusion: We have synthesized a new series of urea/thiourea derivatives bearing 1,2,4-oxadiazole ring. Also, a facile synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from amidoximes and acyl chlorides under microwave irradiation was reported. The compounds were characterized using FTIR, 1H NMR, 13C NMR, and elemental analysis techniques

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Imides are an important class of compounds found in the structure of many biologically active and natural compounds. Imides are also important starting materials used in the synthesis of many heterocyclic compounds. Therefore, the synthesis of these compounds has attracted considerable attention and several innovative methods have been developed. Herein, the synthesis of acyclic imides has been reported from nitriles and carboxylic anhydrides in the presence of catalytic amounts of ptoluenesulfonic acid (PTSA) or H2SO4 under microwave irradiation. The reaction has proceeded in better yields with PTSA. When sulfuric acid was used, the product was obtained in lower yields since the degradation was increased. This new microwave-assisted method is compared with conventional heating, and the other methods, reported in the literature. The main advantages of this procedure are shorter reaction times, easier work-up, and good yields.