Iron-Mediated Synthesis of Isoxazoles from Alkynes: Using Iron(III) Nitrate as a Nitration and Cyclization Reagent

A simple and direct method for the iron(III) nitrate-mediated synthesis of isoxazoles from alkynes has been developed; both self-coupling and cross-coupling products could be successfully prepared from alkynes. Meanwhile, for the cross-coupling and cyclizing of two different alkynes examined, the iron-mediated system shows a good chemoselectivity for the synthesis of corresponding isoxazoles. In our method, cheap and eco-friendly iron(III) nitrate is used as the nitration and cyclization reagent, and KI is used as the additive; they both play a positive role in this transformation. Furthermore, a different mechanism for the formation of isoxazoles from alkynes has been proposed.