Process for preparation of esters in aqueous solvent systems

Abstract

The invention discloses a preparation method of ester in a water-containing solvent system, which comprises the following steps: reacting at least one carboxyl-containing compound with at least one O-alkyl isourea in the water-containing solvent system to obtain the ester, wherein the reaction temperature is controlled between 0 DEG C and the solvent reflux temperature, the molar ratio of the carboxyl-containing compound to the O-alkyl isourea is (0.02-50): 1, and the O-alkyl isourea is a compound represented by a general formula (I): in the general formula (I), R1 is cyclohexyl or isopropyl, R2 is cyclohexyl or isopropyl, and R3 is C1-C4 alkyl. O-alkyl isourea is used as a coupling agent and an alkyl donor, the implementation of carboxylic acid esterification reaction in an aqueous medium is realized, the method is suitable for esterification reaction of water-soluble carboxyl-containing compounds with biological activity, the range of oil-water partition coefficients of esterification synthesis reactants is expanded, and the reaction efficiency is improved. The application field of carboxyl compounds which are soluble in water and insoluble in grease is expanded, and the application range of an esterification reaction molecular modification method is widened.

Description

technical field [0001] The application belongs to the technical field of organic chemistry, and in particular relates to a method for preparing esters in an aqueous solvent system. Background technique [0002] Ester group is one of the most basic and important groups in organic synthetic chemistry, and plays an important role in drug synthesis, polymer synthesis, biomaterial modification and nanomaterial modification. Usually the direct esterification of carboxyl and hydroxyl is the main method for the synthesis of carboxylic acid esters. Since the esterification reaction is a reversible equilibrium reaction, it is usually necessary to remove the water in the system to move the equilibrium to the direction of the esterification reaction to ensure that the reaction proceeds. [0003] Esterification has completed the transition from laboratory to industrialized large-scale production, and is a pillar industry in chemical production. Concentrated sulfuric acid catalysis, acid...

AI Technical Summary

Problems solved by technology

However, the water generated by the esterification reaction will consume a large amount of catalyst in the system, and the consumption amount will even exceed the amount participating in the reaction.

Especially in actual production, a slight change in the water content of the reaction system will seriously affect the composition and degree of esterification of the product. Even if the ratio of raw materials is the same, the quality of the product is difficult to stabilize. This is also difficult in the prior art for partial esterification. solved problem

Moreover, in order to avoid the loss of excess reaction capacity of dehydrating agent catalysts, the reactants and solvent system can be dried before the reaction to purify the raw materials and adjust the water content, but the additional processing steps will cause cumbersome process and increase the cost ; Moreover, when the water content of the reaction system is unknown, the amount of catalyst used is uncontrollable, which brings great challenges to the precise feeding of catalysts in industrial production

[0008] On the one hand, a large number of carboxyl compounds that are easily soluble in water and poorly soluble in oil cannot be dissolved and / or dispersed in an anhydrous solvent system, and thus cannot be effectively dispersed in the reaction system; on the other hand, the existing reaction conditions that strictly control water It is very easy to cause intramolecular or intermolecular dehydration of the compound, destroy the original configuration of the carboxylic acid compound, and cannot maintain its unique biological activity and lose its function. Therefore, the green esterification synthesis method using a dehydrating agent as a catalyst cannot be applied to compounds with biological activity. , water-soluble carboxyl-containing compounds

Images