Borate-catalysed direct amidation reactions of coordinating substrates

Area of Science:

• Organic Chemistry
• Catalysis
• Green Chemistry

Background:

• Amidation reactions are crucial for synthesizing amides.
• Boron-based catalysts offer potential for efficient amidation.
• Challenges exist in catalyst activity and substrate scope for boron catalysts.

Purpose of the Study:

• To investigate the catalytic activity of different boron catalyst classes in amidation.
• To identify a highly reactive and broadly applicable boron catalyst for amidation.
• To understand the deactivation mechanism of boronic acid catalysts.

Main Methods:

• Screening of various boronic acids and borate esters as catalysts.
• Testing catalyst performance with different amine/carboxylic acid substrate pairs.
• Investigating catalyst deactivation using spectroscopic methods.

Main Results:

• Simple boronic acids showed limited substrate scope, being inactive with 2-aminopyridine.
• Borate ester catalysts exhibited moderate activity across tested substrates.
• A novel borate ester catalyst demonstrated high reactivity with challenging substrates.
• The deactivation of boronic acids by 2-aminopyridine was attributed to boroxine stabilization.

Conclusions:

• Novel borate ester catalysts offer effective and scalable amidation.
• The developed method provides an accessible route for synthesizing amides.
• Understanding catalyst deactivation mechanisms is key to designing improved boron catalysts.