Preparation Of The Functionalized Benzothiazole Ionic Liquids And Research In Catalytic Reaction

The ionic liquid is widely used in the field of organic synthesis because of its characteristics of non-volatile, high stability and changeable structure. Four novel acidic ionic liquid was prepared by using benzothiazole as a raw material. They are as follows:[(CH2)3SO3HBth][CH3SO3],[(CH2)3SO3HBth][OTs],[(CH2)3SO3HBth][H2PO4] and [(CH2)3SO3HBth][HSO4]. Their solubility, acidity, and thermodynamic properties were characterized using some methods. Through molecular simulation technology, we found the main factors of affecting the acidity of ionic liquids was the interaction between the proton on the sulfonic acid groups and the anion, this conclusion is consistent with the experimental results. The ionic liquids [(CH2)3SO3HBth][HSO4] were used for catalyzing the ketalization of cyclohexanone with glycol. The optimal reaction conditions was attained as follows:n(cyclohexanone):n(glycol)=1:2, catalyst amount was0.05mol/1mol cyclohexanone, the amount of water carrying agent was1000mL/1mol cyclohexanone, reaction time was3h. Under that condition, yield of product was over97.30%. Additionally, the catalyst had good stability and the catalytic activity. The catalytic activity was almost not decreased significantly after reused for five times. In order to overcome the drawback of ionic liquid with the complicated recovery, silica-immobilized acidic ionic liquid [(CH2)3SO3HBth]HSO4/silica gel was prepared by silica sol-gel method. Through characterization of IR, acidity and thermodynamic properties, we found that the silica-immobilized acidic ionic liquid had a high acidity and thermal stability. The ionic liquids [(CH2)3SO3HBth]HSO4/silica gel was used for catalyzing the ketalization of benzaldehyde with glycol. The optimal reaction conditions was attained as follows: n(benzaldehyde):n(glycol)=1:1.5, catalyst amount was0.053g, the amount of water carrying agent was800mL/1mol benzaldehyde, reaction time was3h. Under that condition, yield of product was over98.99%and the catalyst could be recycled and reused many times. In addition, the catalyst also showed excellent catalytic activity in catalyzing the condensation reaction between the different aldehyde (ketone) and various alcohols. It is shows that the catalyst can be applied to the general acetal (ketal) reaction.