Issue 19, 2020

Rationalizing the diverse reactivity of [1.1.1]propellane through σ–π-delocalization

Abstract

[1.1.1]Propellane is the ubiquitous precursor to bicyclo[1.1.1]pentanes (BCPs), motifs of high value in pharmaceutical and materials research. The classical Lewis representation of this molecule places an inter-bridgehead C–C bond along its central axis; ‘strain relief’-driven cleavage of this bond is commonly thought to enable reactions with nucleophiles, radicals and electrophiles. We propose that this broad reactivity profile instead derives from σ–π-delocalization of electron density in [1.1.1]propellane. Using ab initio and DFT calculations, we show that its reactions with anions and radicals are facilitated by increased delocalization of electron density over the propellane cage during addition, while reactions with cations involve charge transfer that relieves repulsion inside the cage. These results provide a unified framework to rationalize experimental observations of propellane reactivity, opening up opportunities for the exploration of new chemistry of [1.1.1]propellane and related strained systems that are useful building blocks in organic synthesis.

Graphical abstract: Rationalizing the diverse reactivity of [1.1.1]propellane through σ–π-delocalization

Supplementary files

Article information

Article type
Edge Article
Submitted
07 Mar 2020
Accepted
10 Apr 2020
First published
13 Apr 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2020,11, 4895-4903

Rationalizing the diverse reactivity of [1.1.1]propellane through σ–π-delocalization

A. J. Sterling, A. B. Dürr, R. C. Smith, E. A. Anderson and F. Duarte, Chem. Sci., 2020, 11, 4895 DOI: 10.1039/D0SC01386B

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