Iron Nitrate-Mediated Selective Synthesis of 3-Acyl-1,2,4-oxadiazoles from Alkynes and Nitriles: The Dual Roles of Iron Nitrate

Abstract

A direct strategy for the selective synthesis of 3-acyl-1,2,4-oxadiazoles from alkynes and nitriles has been developed under iron­(III) nitrate-mediated conditions. The mechanism includes three sequential procedures: iron­(III) nitrate-mediated nitration of alkynes leads to α-nitroketones, dehydration of α-nitroketones provides the nitrile oxides, and 1,3-dipolar cycloaddition of nitrile oxides with nitriles produces 3-acyl-1,2,4-oxadiazoles under iron-mediated conditions. Iron­(III) nitrate plays dual roles in the nitration of alkynes and the activation of nitriles, while the formation of pyrimidine/isoxazole byproducts can be efficiently inhibited.

Oxidative [3+2]Cycloaddition of Alkynylphosphonates with Heterocyclic N-Imines: Synthesis of Pyrazolo[1,5-a]Pyridine-3-phosphonates

“…Fe(NO 3 ) 3 is broadly used as a catalyst in a wide scope of oxidation reactions. Recently, it has been found to be effective in the promotion of 3-acyl-1,2,4oxadiazole synthesis from alkynes and nitriles [45]. Moreover, iron (III) nitrate mediated synthesis of acylisoxazoles from terminal alkynes was reported [46].…”

New efficient synthesis of bis-1,2,4-oxadiazole derivatives via subsequent Staudinger/aza-Wittig reaction

“…There were many synthetic methods [16][17][18][19][20] of oxadiazole, but there were only few literatures on the synthesis of bisoxadiazole ring. diaminoglyoxime, as the only basic starting material, was used to obtain bis-1,2,4oxadiazole derivatives through condensation and cyclization reaction with various reagents, such as triethyl orthoformate 21,22 , triethyl orthoacetate 21 , trifluoroacetic acid 21 , trifluoroacetic anhydride 23 or acetoxyacyl chloride 23,36 and chloroacyl chloride 24 in the existed literatures.…”

Copper‐Catalyzed Three‐Component Cascade Reaction of Benzaldehyde with Benzylamine and Hydroxylamine or Aniline: Synthesis of 1,2,4‐Oxadiazoles and Quinazolines

“…Additionally, some works focused on transforming substrates that contained amidine/guanidinium group to 1,2,4‐oxadiazole scaffold by NBS/iodobenzene diacetate (IBD)‐mediated oxidative cyclization [8] . The latest synthesis strategy uses iron (III) nitrate to mediate the 1,3‐dipolarization of alkynes and nitriles, the iron (III) nitrate plays dual roles in the nitration of alkynes and the activation of nitriles [9] …”