A dienyl boronate‐aryl nitroso ene reaction entry to C‐pyrrolyl nitrones and subsequent conversion to isoxazolidines.

A new cascade reaction to access C‐pyrrolyl nitrones en route to isoxazolidines is reported; a process that involves four successive steps, the first key step being an ene‐reaction of a 3‐methyl‐1,3‐dienylboronate ester with an aryl nitroso compounds to derive uncommon 1,3‐dipoles which react with various alkenes to access isoxazolidines. The scope and mechanism of the cascade sequence is discussed.