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

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.本研究开发了一种以硝酸铁(III)为介导试剂，由炔烃与腈类选择性合成3-酰基-1,2,4-恶二唑的直接合成策略。该反应机制包含三步连续过程：首先由硝酸铁(III)介导炔烃发生硝化反应生成α-硝基酮，随后α-硝基酮经脱水得到腈氧化物，最后在铁介导条件下，腈氧化物与腈类发生1,3-偶极环加成反应生成3-酰基-1,2,4-恶二唑。硝酸铁(III)在炔烃硝化与腈类活化过程中发挥双重作用，同时可有效抑制嘧啶/异恶唑类副产物的生成。