Highly Substituted 2,3-Dihydroisoxazoles by Et₃N-Catalyzed Tandem Reaction of Electron-Deficient 1,3-Conjugated Enynes with Hydroxylamines

An Et₃N-catalyzed tandem reaction of electron-deficient 1,3-conjugated enynes with hydroxylamines was developed which provided rapid, metal-free, and regioselective access to highly substituted multifunctionalized 2,3-dihydroisoxazoles under mild conditions. The reactions of 3-(2-arylethynyl)-4H-chromen-4-ones with hydroxylamines afford β-amino enones under the same reaction conditions.