Reversible Aromaticity Transfer in a Bora-Cycle: Boron-Ligand Cooperation

Area of Science:

• Organic Chemistry
• Organometallic Chemistry
• Materials Science

Background:

• Aromaticity is a fundamental chemical principle.
• Reversible ligand dearomatization is key for bond activation in metal complexes.
• Metal-free systems offer alternative reaction pathways.

Purpose of the Study:

• To explore metal-free dearomatization sequences.
• To synthesize and characterize pyridine-coordinated aminoboranes.
• To investigate aromaticity switching and its application in bond activation.

Main Methods:

• Synthesis of pyridine-coordinated aminoboranes.
• Temperature-induced reactions.
• Nuclear Magnetic Resonance (NMR) spectroscopy.
• Density Functional Theory (DFT) calculations.

Main Results:

• A temperature-induced formal dearomatization of the pyridine ring was observed.
• An aromaticity switch occurred, forming a six-π-electron boron-containing heteroaromatic system.
• Coordination of amine or carboxylic acid disrupted aromaticity, enabling N-H and O-H bond cleavage.

Conclusions:

• The metal-free system demonstrates reversible aromaticity switching.
• This process facilitates unprecedented N-H and O-H bond activation.
• The findings open new avenues in synthetic chemistry and catalysis.