Stereodivergent (3 + 2)-cycloaddition of donor-acceptor cyclopropanes and citral imines catalyzed by Yb(NTf2)3/PyBOX
Pavel G Sergeev1, Roman A Novikov1, Yury V Tomilov1
1N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation. novikovfff@bk.ru.
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.
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Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

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