Deep eutectic solvents(DES) is a new type of environmentally green solvents. Compared with conventional organic solvents, DES have more advantages, such as negligible vapor pressure, non-flammability, good chemical and thermal stability, non-toxicity, biodegradability, recyclability and low price among others. As a new type of solvent, DES has an extremely extensive application prospect. The latest research results of DES is reviewed in this paper. DES as a novel solvent and catalyst was applied in the traditional organic synthesis reaction, mainly including Helogenation reaction, Diels-Alder reaction, Knoevenagel reaction, Henry reaction, Perkin reaction, Paal-Knorr reaction, Biginelli reaction. At last, we hope that DES has a good application prospect in the field of organic synthesis.

Contents
1 Introduction
2 DES in the replacement reaction
2.1 Alkylation of nitrogen
2.2 Alkylation of the alcohol
2.3 Friedel-Crafts alkylation reaction
2.4 Halogenation
2.5 Esterification
3 DES in addition reactions
3.1 Diels-Alder reaction
3.2 Henry reaction
3.3 Cycloaddition
4 DES in condensation reaction
4.1 Knoevenagel condensation
4.2 Perkin reaction
5 DES in the cyclization
5.1 Fischer indole synthesis
5.2 Paal-Knorr reaction
5.3 Biginelli reaction
6 DES in the elimination reactions
7 DES in rearrangement reactions
8 DES in reducing reactions
9 Conclusions and outlook