A Versatile Iron‐Catalyzed Protocol for the One‐Pot Synthesis of Isoxazoles or Isoxazolines from the Same Propargylic Alcohols

The use N-sulfonyl-protected hydroxylamines as bi-nucleophiles in iron-catalyzed propargylic substitutions allows the selective one-pot synthesis of four classes of substituted isoxazoles or isoxazolines from the same propar- gylic alcohols (21 examples) by simply tuning the nature of the base. By using an ironA catalyst and a base such as triethylamine (3 equiv), isoxazoles 3 are obtained in good isolated yields (56-95%), whereas N-sulfonyl-protect- ed isoxazolines 6 are selectively ob- tained (77-93% yield) by using iron and gold catalysts in the presence of a catalytic amount of pyridine (10 mol%).