Boron-mediated sequential alkyne insertion and C-C coupling reactions affording extended π-conjugated molecules

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Main Group Chemistry

Background:

• C-C bond coupling reactions are fundamental in organic synthesis.
• Organotransition metal complexes typically mediate these transformations.
• There is a need for alternative, efficient synthetic methodologies.

Purpose of the Study:

• To demonstrate a novel C-C bond coupling strategy using a borafluorene derivative.
• To explore sequential alkyne insertion and deborylation/coupling reactions.
• To synthesize complex aromatic and π-conjugated systems.

Main Methods:

• Utilizing a borafluorene with a B-Cl moiety.
• Sequential reactions involving alkyne insertion (1,2-carboboration).
• One-electron oxidation to trigger deborylation and Csp(2)-Csp(2) coupling.

Main Results:

• Efficient formation of borepin derivatives via carboboration.
• Successful synthesis of phenanthrene frameworks through oxidation-induced coupling.
• In situ transformation to dibenzo[g,p]chrysene derivatives under excess oxidant conditions.

Conclusions:

• The borafluorene reagent mediates sequential C-C bond formations effectively.
• This method provides a powerful new synthetic tool for extended π-conjugated systems.
• The findings advance the understanding of main group element reactivity in organic synthesis.