Facile synthesis of monomeric alumatranes

Area of Science:

• Organometallic Chemistry
• Supramolecular Chemistry
• Lewis Acid Catalysis

Background:

• Alumatranes are tricyclic molecules with a transannular N --> Al bond.
• They function as Lewis acids, activating substrates at the axial coordination site.

Purpose of the Study:

• To synthesize and characterize novel dimeric alumatranes.
• To investigate their reactivity with various substrates.
• To explore their catalytic potential in organic reactions.

Main Methods:

• Treatment of tris(2-hydroxy-3,5-dimethylbenzyl)amine with AlMe(3) to form dimeric (AlL)(2).
• X-ray diffraction analysis for structural elucidation.
• Reactions with oxygen and nitrogen donors, including water and benzaldehyde.
• Catalytic testing in the benzaldehyde and trimethylsilyl cyanide reaction.

Main Results:

• Synthesis of dimeric alumatrane (AlL)(2) 1 and its characterization.
• Formation of various alumatranes (2-6) upon reaction with different substrates.
• Observation of structural changes and varying transannular bond distances.
• Hydrolysis of alumatrane 6 to form a complex framework 7, existing in polymorphic forms (7a, 7b).
• Dimeric alumatrane 1 catalyzed the synthesis of 2-trimethylsilyoxyphenylacetonitrile with 95% yield.

Conclusions:

• Dimeric alumatranes are versatile Lewis acids capable of substrate activation.
• The coordination of apical ligands influences the aluminum center's electronic properties.
• Alumatranes can form complex supramolecular frameworks upon hydrolysis.
• Dimeric alumatrane 1 shows significant catalytic activity in organic transformations.