Synthesis of 4-Phosphonylpyrrolidin-3-ones via [3+2] Cycloaddition of Nitrones with Phosphinylallenes

A variety of 4-phosphinylpyrrolidin-3-ones was prepared in good yields and excellent diastereoselectivity via a [3+2] cycloaddition between aryl aldonitrones and phosphinylallenes. Under the reaction conditions, the cycloadducts directly undergo a rearrangement to afford selectively the corresponding pyrrolidin-3-ones. DFT calculations provide some insights into the mechanism.