Highly efficient and green esterification of carboxylic acids in deep eutectic solvents without any other additives

ABSTRACT

A protocol that carboxylic acids esterifies with the quaternary ammonium salt of deep eutectic solvent (DES) is presented, which opens a new access to ester using DES as alkylating agent, solvent, and catalyst. The reaction runs smoothly in DES without any other additives. Substituted cinnamic acids, aromatic acids, and aliphatic acids can be esterified in moderate to good yields. The advantages of this reaction include excellent functional group compatibility and simple reaction procedure.

GRAPHICAL ABSTRACT

KEYWORDS:

• Carboxylic acids
• catalyst-free
• deep eutectic solvent
• esterification

Notes

¹Note: In consideration of the decomposition of quaternary ammonium salt in deep eutectic solvent, tertiary amines were put into the reaction and the results were listed in Table 2 (Entries 5 and 6), the results of Table 2 showed that tertiary amines were not good alkylating agent of carboxylic acids.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (81374062 and 85673179), the Natural Science Foundation of Hunan Province (2015JJ6082), the Education Department of Hunan Province (17C1192), and Hunan Science and Technology Department Funds (2014SK4037, 2014FJ1007).