Phosphane‐Catalyzed [4+1] Annulation between Nitroalkenes and Morita–Baylis–Hillman Carbonates: Facile Synthesis of Isoxazoline N ‐Oxides by Phosphorus Ylides

A phosphane‐catalyzed [4+1] annulation between nitroalkenes and Morita–Baylis–Hillman carbonates has been realized; this provides facile and diastereoselective access to polysubstituted isoxazoline N‐ oxides in moderate to excellent yields. In the annulation, an in situ formed allylic phosphorus ylide presumably serves as a pivotal active intermediate. This reaction accordingly represents the first example of phosphorus ylide initiated [4+1] cyclization of nitroalkenes to give isoxazoline N ‐oxides.