Stereodivergent (3 + 2)-cycloaddition of donor–acceptor cyclopropanes and citral imines catalyzed by Yb(NTf2)3/PyBOX

Abstract

The idea of (3 + 2)-construction of pyrrolidines is realized based on a common natural substrate modified at a single position by functional groups with opposite electronic effects. Their role in switching the diastereoselectivity mode of cycloaddition is shown for the first time. In this work, Lewis-acid-complex-catalyzed (3 + 2)-cycloaddition reactions involving donor–acceptor cyclopropanes (DACs) and newly obtained citral imines were investigated and optimized. Based on the results obtained, a method for the diastereoselective synthesis of substituted 2,5-cis- and trans-pyrrolidines was developed. Our approach demonstrates broad substrate scope and significant synthetic utility, as evidenced by the directed product derivatization. This work expands the applicability of the known method to a wider range of aliphatic substrates due to the decisive participation of Yb(NTf₂)₃/PyBOX as a catalyst.