Related Experiment Video
Updated: Sep 8, 2025

Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry
Published on: March 4, 2021
A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole
Harrison M Bergman1, D Dawson Beattie1, Gavin R Kiel1
1Department of Chemistry, University of California Berkeley California 94720 USA tdtilley@berkeley.edu.
This study introduces stannoles as stable diene equivalents for synthesizing polycyclic aromatic hydrocarbons (PAHs). This novel approach overcomes limitations in current Diels-Alder reactions, enabling efficient π-extension for larger PAH structures.
Area of Science:
- Organic Chemistry
- Materials Science
- Nanotechnology
Background:
- Synthesis of polycyclic aromatic hydrocarbons (PAHs) and nanographenes relies on efficient ring fusion.
- Diels-Alder cycloaddition is a key method, but faces challenges with diene accessibility, stability, and adduct aromatization.
- Current limitations hinder the expansion of structural diversity in PAHs.
Purpose of the Study:
- To overcome limitations in Diels-Alder based PAH synthesis.
- To develop a modular strategy for accessing a wider range of PAHs and nanographenes.
- To introduce stannoles as versatile diene equivalents in cycloaddition reactions.
Main Methods:
- Employed a formal Cp2Zr-mediated [2 + 2 + 1] cycloaddition to create stannole-annulated PAHs.
- Utilized the synthesized stannoles as diene components in a subsequent [4 + 2] cycloaddition/aromatization cascade with arynes.
- Developed a modular synthesis for stannole precursors.
Main Results:
- Successfully generated stannole-annulated PAHs via a [2 + 2 + 1] cycloaddition.
- Demonstrated the utility of stannoles as reactive yet handleable diene equivalents in [4 + 2] cycloadditions with arynes.
- Achieved π-extension to afford larger, complex PAH structures.
Conclusions:
- Stannoles are effective diene equivalents, overcoming key limitations of traditional Diels-Alder strategies for PAH synthesis.
- The developed modular strategy and the use of stannoles significantly expand the accessible structural diversity of PAHs.
- This approach provides a powerful new route for constructing complex polycyclic aromatic hydrocarbons and related nanographenes.
Related Concept Videos
Cycloaddition Reactions: Overview
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal and Photochemical Electrocyclic Reactions: Overview
Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.

