Strongly Acidic Deep Eutectic Solvent As Promoting And Recyclable Medium For Organic Synthesis

Deep eutectic solvent(DES)is a kind of solvent similar to ionic liquid,which is composed normally of a hydrogen bond donor and a hydrogen bond acceptor.Because of its simple preparation procedure,low cost and tunable composition and properties,they can usually be used as a new generation of green solvent for organic synthesis and separations.Deep eutectic solvent is usually neutral or weak alkaline.Although acidic catalysts have been widely used in organic synthesis,and searching for new and green alternative acid catalysts is also hard task of green and catalytic chemists.Until now,little attention has been paid to strongly acidic DES.In this thesis,a kind of strongly acidic DES was developed,which was then used as a catalyst in some organic transformations.The DES catalyst can be recycled and reused at least for five times with only little decrease of its catalytic activity in the first reaction,and in the second reaction,the activity of DES decreased about 10% which may d ue to the loss of DES in the transformation.Meanwhile,the DES catalyst was also characterized by FT-IR and TGA.And FT-IR investigation showed that hydrogen bond was indeed formed in the DES system composed of PTSA and PEG4000.TGA study revealed that the acidic DES is quite stable,and no decomposition was observed below 200 °C.The strongly acidic DES was examined in the following three organic transformations:1.Three-component reaction of salicylaldehyde,styrene and light alcohol.With the aid of the PEG4000/PTSA DES system,and 3,4-dihydrobenzopyran can be obtained in moderate to good yield.This reaction has not been reported before.2.Condensation of cinnamic acid and phenol to form coumarin.PEG4000/PTSA was proven to be an effective and recyclable catalyst for this transformation.3.Indole to carbazole transformation by using 2-arylindole and 1,2-diketone as starting materials.This paper not only develops a new type of homogeneous catalytic system of strongly acidic DES,but also realizes the green transformation of partial acid catalysis.