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Rationalizing the diverse reactivity of [1.1.1]propellane through sigma-pi-delocalization

preprint
revised on 05.02.2020 and posted on 07.02.2020 by Alistair Sterling, Alexander Durr, Russell C. Smith, Edward Anderson, Fernanda Duarte

[1.1.1]Propellane has gained increased attention due to its utility as a precursor to bicyclo[1.1.1]pentanes (BCPs) – motifs of high value in pharmaceutical and materials research – by addition of nucleophiles, radicals and electrophiles across its inter-bridgehead C–C bond. However, the origin of this broad reactivity profile is not well-understood. Here, we present a comprehensive computational study that attributes the omniphilicity of [1.1.1]propellane to a moldable, delocalized electron density, characterized by the mixing of the inter-bridgehead C–C bonding and antibonding orbitals. Reactions with anions and radicals are facilitated by stabilization of the adducts through sigma-pi-delocalization of electron density over the cage, while reactions with cations involve charge transfer that relieves Pauli repulsion inside the cage. These results provide a unified framework to rationalize propellane reactivity, opening up opportunities for the exploration of new chemistry of [1.1.1]propellane and related strained systems.

History

Email Address of Submitting Author

fernanda.duartegonzalez@chem.ox.ac.uk

Institution

University of Oxford

Country

United Kingdom

ORCID For Submitting Author

0000-0002-6062-8209

Declaration of Conflict of Interest

The authors declare no competing financial interest.

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