Synthesis of 4‐Phosphinylpyrrolidin‐3‐ones via [3+2] Cycloaddition of Nitrones with Phosphinylallenes

Abstract A variety of 4‐phosphinylpyrrolidin‐3‐ones was prepared via a [3+2] cycloaddition between aryl aldonitrones and phosphinylallenes. The products were isolated as unique 4,5‐ trans diastereomers, in yields between 47% and 80%, over 23 examples. In the case of chiral racemic allenes, a 2:1 to 4:1 moderate 2,5‐diastereoselectivity was observed. 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, involving the homolytic cleavage of the N−O bond of the cycloadduct. magnified image