One-pot synthesis of isoxazoles from enaminones: an application of Fe(II) as the catalyst for ring expansion of 2H-azirine intermediates

We report an application of FeCl₂ as an inexpensive, nontoxic, and efficient catalyst in a clean ring expansion reaction of 2H-azirine derivatives, an intermediate formed through the PhI(OAc)₂-mediated azirination of readily available enaminones. An alternative one-pot protocol for the synthesis of various substituted isoxazoles from their corresponding enaminones has been further established based on this reaction, and herein described.