Chiral <i>N</i> , <i>N</i> ′-Dioxide/Magnesium(II)-Catalyzed Enantioselective [3,3]-Sigmatropic Rearrangement of 3-Propargyloxyflavones

A chiral <i>N</i>,<i>N</i>'-dioxide/Mg(II) catalytic system was developed for the efficient promotion of the enantioselective [3,3]-sigmatropic rearrangement of 3-propargyloxyflavones. Diverse allene-containing 3-propargyloxyflavone derivatives were thus obtained in moderate to good yields and excellent ee values. Mechanism investigations revealed that water serves as an accelerator for this transformation, while the C-H···π interaction between the catalyst and the chromone substrates constitutes a rational explanation for chiral recognition.