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Reactivity Studies of Donor-Acceptor Cyclopropanes: Is there a Relation to Structural and Electronic Properties?

Affiliation
Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, 38106, Braunschweig, Germany.
Kreft, Alexander;
Affiliation
Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, 38106, Braunschweig, Germany.
Lücht, Alexander;
Affiliation
Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, 38106, Braunschweig, Germany.
Grunenberg, Jörg;
Affiliation
Technische Universität Braunschweig, Institut für Anorganische und Analytische Chemie, Hagenring 30, 38106, Braunschweig, Germany.
Jones, Peter G;
ORCID
0000-0002-3973-2212
Affiliation
Technische Universität Braunschweig, Institut für Organische Chemie, Hagenring 30, 38106, Braunschweig, Germany.
Werz, Daniel B

The kinetics of (3+2) cycloaddition reactions of 18 different donor-acceptor cyclopropanes with the same aldehyde were studied by in situ NMR spectroscopy. Increasing the electron density of the donor residue accelerates the reaction by a factor of up to 50 compared to the standard system (donor group=phenyl), whereas electron-withdrawing substituents slow down the reaction by a factor up to 660. This behavior is in agreement with the Hammett substituent parameter σ. The obtained rate constants from the (3+2) cycloadditions correlate well with data from additionally studied (3+n) cycloadditions with a nitrone (n=3) and an isobenzofuran (n=4). A comparison of the kinetic data with the bond lengths in the cyclopropane (obtained by X-ray diffraction and computation), or the 1 H and 13 C NMR shifts, revealed no correlation. However, the computed relaxed force constants of donor-acceptor cyclopropanes proved to be a good indicator for the reactivity of the three-membered ring.

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License Holder: This is the peer reviewed version of the following article: Kinetic Studies of Donor–Acceptor Cyclopropanes: The Influence of Structural and Electronic Properties on the Reactivity, which has been published in final form at https://doi.org/10.1002/anie.201812880. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

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