Replacing polar aprotic solvents with water in organic synthesis

In contrast to the risks of traditional polar aprotic solvents to health, safety, and environment, water with many advantages, such as abundance, environmental compatibility, has been regarded as ideal alternative to polar aprotic solvents in organic synthesis. However, inferior reaction rate caused by depressed solubility of organic compounds and instability of water-incompatible catalysts in water hinders practical and wide utilization of water as reaction medium. Strategies employed to solve the abovementioned issues in synthetic reactions have been summarized in this review, including the use of task-specific surfactant-based catalysts in pure water and the use of water-containing cosolvents. The two comple-mentary strategies are desired to give a brighter future for replacing hazardous polar aprotic solvents with water. In addition, with the aid of pluralistic and innovative technologies, for example, biomimetic catalysis and continuous-flow reac-tion, the replacement of polar aprotic solvents with water in a large scale could be around the corner.