A chiral N,N′-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.
Liu et al. (Wed,) studied this question.