A Diversified Assembly of 1,2,4-Oxadiazol-3-amines: Metallic Thiophile Catalyzed Chemoselective One-Pot Reaction of Aryl Isothiocyanates, Amidines/Guanidines, and Hydroxylamine

Abstract

An efficient one-pot synthesis of 1,2,4-oxadiazol-3-amines from simple starting materials, isothiocyanates, amidines/guanidines, and hydroxylamine, is described. The reaction is facilitated by metallic-thiophile-assisted desulfurization of in situ formed amidino-or guanidinothiourea to give chemoselectively Nhydroxyguanidine intermediates that give exclusively various 1,2,4-oxadiazol-3-amines in good to excellent yields. The reaction mechanistic pathway may proceed through an intramolecular 5-exotrig cyclization.

Past, present and future of ecotourism, a systematic literature review from last decade.

“…The people who are related to the livelihood, positive word of mouth create opportunities for the livelihood sector gradually. That is a positive sign for people are involved in timber smuggling and fishing turn to ecotourism activities, the reason is tourism is a higher income-generating sector [20]. The proper and conceptual interpretation of ecotourism explains that all problems situated with the tourism solved by the ecotourism., like economic development, environmental conversation, poverty reduction, and cultural preservation with the aim to educate the tourists about all problems [2].…”

Facile synthesis of N-1,2,4-oxadiazole substituted sulfoximines from N-cyano sulfoximines

“…Our proposed approach relied on the conventional construction of the N -1,2,4-oxdiazole ring from a N -hydroxy guanidine type intermediate of sulfoximine (Method E , Scheme 1). Construction of oxadiazole amidoxime derivatives has been well documented 11 but relatively few reports 12 exist for the same from N -hydroxyguanidine type intermediates. We perceived that employing this ring construction approach would be better than developing a new metal catalyzed N-heteroarylation method.…”

1,3-Dipolar Cycloaddition Reaction of Nitrile Oxide to Thiocyanates: An Efficient and Eco-Friendly Synthesis of N-Aryl-2-((3-aryl-1,2,4-oxadiazol-5-yl)thio)acetamides

“…11 Among the different strategies available for the synthesis of 1,2,4-oxadiazole derivatives, the more popular procedures involve reactions of amidoximes with carboxylic acids, [12][13][14] carboxylic acid chlorides, 15,16 dicarboxylic acid anhydrides, 17,18 aldehydes, 19 Erlenmeyer azlactones, 20 protected amino acids, 21 benzoyl cyanides, 22 nitrilium salts, 23 and oxidative cyclization by DDQ. 24 The formation of this scaffold was also accomplished by the reaction of hydroximoyl chloride with aryl thiocyanates, 25,26 hydroxylamine with cyanamides, 27 and by one-pot reactions of hydroxylamine involving either aryl isothiocyanates and amidines 28 or nitriles and Meldrum's acid. 29 Other notable methods that afforded the 1,2,4-oxadiazoles employed substrates such as nitriles, [30][31][32] N-(cyanomethyl)amide, 33 and nitrosoimidazoles.…”