Formamide catalyzed activation of carboxylic acids - versatile and cost-efficient amidation and esterification

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Amide and ester bond formation are fundamental transformations in organic synthesis.
• Existing methods often suffer from low yields, poor functional group compatibility, or high cost.
• Trichlorotriazine (TCT) is a cost-efficient reagent for activating hydroxyl groups.

Purpose of the Study:

• To develop a novel, broadly applicable, and cost-efficient method for amide C-N and ester C-O bond formation.
• To utilize formylpyrrolidine (FPyr) as a Lewis base catalyst in conjunction with TCT.
• To enhance reaction yields, functional group tolerance, and scalability compared to existing methods.

Main Methods:

• Employing formylpyrrolidine (FPyr) as a Lewis base catalyst.
• Utilizing trichlorotriazine (TCT) for OH-group activation at ≤40 mol% loading.
• Investigating functional group compatibility, including acid-labile groups and peptide synthesis.
• Rationalizing mechanistic enhancements through acid chloride intermediates.

Main Results:

• Achieved high yields for amide bond formation (e.g., 26% to 91%) and the first synthetically useful yields for esterification.
• Demonstrated excellent cost-efficiency (E-factor down to 3) and scalability (up to >80 g).
• Showcased high functional group compatibility, including acetals, silyl ethers, and peptide C-N bonds.

Conclusions:

• The FPyr/TCT system provides a superior method for amide and ester synthesis.
• This approach offers significant improvements in yield, cost, waste reduction, and scalability.
• The method is broadly applicable and compatible with sensitive functional groups, advancing synthetic organic chemistry.