Related Experiment Video
Updated: Jul 5, 2025

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Taming nonclassical carbocations to control small ring reactivity
Ryan E McNamee1, Nils Frank1, Kirsten E Christensen1
1Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, UK.
Abstract:
Prediction of the outcome of ring opening of small organic rings under cationic conditions can be challenging due to the intermediacy of nonclassical carbocations. For example, the solvolysis of cyclobutyl or cyclopropylmethyl derivatives generates up to four products on nucleophilic capture or elimination via cyclopropylcarbinyl and bicyclobutonium ions. Here, we show that such reaction outcomes can be controlled by subtle changes to the structure of nonclassical carbocation. Using bicyclo[1.1.0]butanes as cation precursors, the regio- and stereochemistry of ring opening is shown to depend on the degree and nature of the substituents on the cationic intermediates. Reaction outcomes are rationalized using computational models, resulting in a flowchart to predict product formation from a given cation precursor.
Related Concept Videos
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
Acid-Catalyzed Ring-Opening of Epoxides
Radical Reactivity: Intramolecular vs Intermolecular
Radical Reactivity: Steric Effects
Along with electronic...
ortho–para-Directing Deactivators: Halogens

![Solid-phase Synthesis of [4.4] Spirocyclic Oximes](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F58508.jpg&w=3840&q=50)