Gold-catalyzed cyclization and subsequent arylidene group transfer of O-propioloyl oximes

Gold-catalyzed cyclizations of O-propioloyl oximes via C-N bond formation followed by arylidene group transfer were successfully carried out to afford the corresponding 4-arylideneisoxazol-5(4H)-ones in good to excellent yields. As an example, (E)-benzaldehyde O-3-phenylpropioloyl oxime (1a) was reacted in acetonitrile at 25 °C in the presence of Au(PPh₃)NTf₂ (5 mol %) to give 4-benzylidene-3-phenylisoxazol-5(4H)-one (2a) in 90% yield. On the basis of crossover experiments, the arylidene "migration" was shown to proceed in an intermolecular manner.