Intramolecular pyridine-based frustrated Lewis-pairs

Area of Science:

• Organometallic Chemistry
• Boron Chemistry
• Organic Synthesis

Background:

• Methylpyridines are versatile organic compounds.
• Organoboron compounds are important synthetic intermediates.
• Intramolecular interactions can significantly affect chemical reactivity.

Purpose of the Study:

• To synthesize novel borylmethylpyridine derivatives.
• To investigate the structural and electronic properties of these compounds.
• To explore the reactivity of borylmethylpyridines towards various substrates.

Main Methods:

• Deprotonation of methylpyridines using strong bases (n-butyllithium, n-butyllithium/KO-t-Bu).
• Reaction of organometallic intermediates with chlorobis(pentafluorophenyl)borane (ClB(C6F5)2).
• Crystallographic analysis and H/D-scrambling experiments to study structure and reactivity.

Main Results:

• Formation of monomeric 2-borylmethylpyridines with intramolecular B-N bonds and four-membered rings.
• Observation of a short B-N distance in a dimethylamino-functionalized derivative, correlating with low reactivity.
• Hydroboration of a functionalized pyridine yielded a product lacking intramolecular B-N bond formation due to steric hindrance.
• Demonstrated reactivity towards hydrogen in H/D-scrambling experiments.

Conclusions:

• The synthesized borylmethylpyridines exhibit unique structural features with intramolecular B-N bonding.
• Steric and electronic factors, particularly the B-N interaction, govern the reactivity of these compounds.
• These findings contribute to the understanding of organoboron chemistry and the design of novel functional molecules.