Deep Eutectic Solvents（ZnCl₂/ChCl） Catalyzed Friedel-Crafts Reaction

At the beginning of this century, scientists discovered a special solvent- Deep Eutectic Solvents(DES), a novel solvent and catalyst. Compared with the traditional organic solvent, DES has several advantages such as a low vapor pressure, non-flammable, good stability, non-toxic, biodegradable, recyclable, easily available. Thus it is called new green solvent and catalyst, and has a wide application prospect. As novel reaction medium or catalyst, DES has been used in traditional organic synthesis reactions, for example, halo reaction, Diels-Alder reaction, Knoevenagel condensation, Henry reaction, Perkin reaction, Paal-Knorr reaction, Biginelli reaction.Currently DES has not been reported as catalyst in Friedel-Crafts acylation reactions and Friedel-Crafts alkylation reactions in which alcohol compounds as substrate. In this paper, some new DES were designed and synthesized. Some factors, such as reaction temperature, amount of catalyst and different reaction substrate were investigated. Moreover, the recycling and reuse of [Ch Cl] [Zn Cl2]2 were investigated. Finally, the posbile reaction mechanisms were probed. Specific content is as follows:(1) Designed and synthesized a series of DES, investigated the effect on Friedel-Crafts alkylation reaction of electron-rich aromatic compounds with alcohols. Some important factors including the choice of deep eutectic solvent, amount of catalyst, reaction temperature and other conditions were optimized, and the recycling and reuse of DES were also studied. The results showed that in the absence of additional solvent, the optimal reaction conditions were 2.0 eq of [Ch Cl] [Zn Cl2]2 as catalyst and solvent, 80 ?C as reaction temperature, and the yield can reach up to 95 %; DES could be reused for 5 times and the yields could be kept from 87 % to 94 %, which implied that DES was relatively stable.(2) At the same time, different catalysises including DES and several Br?nsted acid ionic liquids(BAILs) were chosen for catalyzing Friedel-Crafts alkylation of 1,2,4-trimethoxybenzene(1a) with Diphenylmethanol(2a). The results showed that the yields catalyzed by BAILs were slightly higher than DES, but during the catalytic process Br?nsted acid was deactivated, acidification was needed to restore activity when it was reused, while DES could be reused directly without activating.(3) Friedel-Crafts acylation reaction of electron-rich aromatic compounds with chloride was investigated., the choice of deep eutectic solvent, catalyst, reaction temperature and other conditions were optimized, and the recycle rate of DES was also studied. The results showed that in the absence of additional solvent, the optimal reaction conditions were 1.0 eq of [Ch Cl] [Zn Cl2]2 as catalyst and solvent, 70 ?C as reaction temperature, and the yield can reach up to 85 %; DES could be reused for 5 times and the yields could be kept from 79 % to 85 %, which implied that DES was relatively stable.(4) In this paper, 29 kinds of compounds were synthesized and characterized by 1H NMR,13C NMR and melting point, in which 6 kinds compounds were novel; 15 kinds of DES including 5 new compounds were synthesized; 7 kinds of BAIL incoulding 1 new compounds were synthesized. The synthesized DES and BAILs(except the ones containing metal ions) were characterized through nuclear magnetic spectra.