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Isolation of an Antiaromatic 9-Hydroxy Fluorenyl Cation
Daniel Duvinage1, Stefan Mebs2, Jens Beckmann1
1Institut für Anorganische Chemie und Kristallographie, Universität Bremen, Leobener Straße 7, 28359, Bremen, Germany.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|April 9, 2021
Summary
Researchers isolated a stable 9-hydroxy fluorenyl cation, a previously transient antiaromatic system. This discovery offers new insights into fluorenyl cation chemistry and stability.
Area of Science:
- Organic Chemistry
- Aromaticity Studies
Background:
- Fluorenyl cations are known 4π electron antiaromatic systems.
- Previously, fluorenyl cations were only observed as short-lived intermediates under harsh conditions like superacidic environments or flash photolysis.
Purpose of the Study:
- To synthesize and characterize a stable fluorenyl cation.
- To investigate the formation pathways of fluorenyl cations under specific reaction conditions.
Main Methods:
- Attempted synthesis of a m-terphenyl acylium cation via fluoride abstraction from benzoyl fluoride.
- Characterization of the resulting stable cation.
Main Results:
- An isolable 9-hydroxy fluorenyl cation was formed instead of the target acylium cation.
- The cation formation involved an intramolecular electrophilic attack on a mesityl group, followed by a 1,2-methyl shift and proton transfer to oxygen.
Conclusions:
- The study reports the first isolable 9-hydroxy fluorenyl cation.
- The findings demonstrate a novel pathway for generating stable fluorenyl cations, expanding knowledge beyond transient intermediates.
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