Microwave-assisted Dynamic Ki- Netic Resolution Of Aromatic Sec-Alcohols

On the basis of successful kinetic resolution (KR) and racemization, the racemi-zation catalysts were combined in one pot with the biocatalyst Novozym 435 to per-form the dynamic kinetic resolution (DKR) under microwave heating. Fot granted the influence of microwave irradiation was compared to conventional heating. Results showed that the use of microwave irradiation, in most cases, could enhance the reac-tion rate in KR, racemization and DKR dramatically.Firstly, effects of different reaction parameters including solvent, temperature, enzyme loading and acyl donor were investigated in the KR of 1-phenylethanol by microwave heating. Under the optimum condition (solvent:petroleum ether, tempera-ture:50℃, enzyme loading:8 mg/mL), reaction rate of 2-4 fold over conventional heating was obtained using microwave. And high conversion (>49%) and eep (>99%) were achieved with two types acyl donors, alkene ester and phenolic ester.Secondly, the transformation of the unwanted enantiomer was studied by race-mization. Effects of reaction conditions, such as temperature and solvents were inves-tigated on four racemization catalysts, acid resin Purolite (?) CT151, TiO2/SO42-, ZrO2/SO42- and sulfonated sepiolite. Petroleum ether was the optimum solvent for Purolite CT151 and toluene was for the others under microwave irradiation. The formation of the secondary product styrene could be strongly suppressed at lower temperature. So 40℃ was chosed. Totally the racemization rate was strongly en-hanced by microwave. Additionaly, the catalysts were characterized by BET, aperture, FT-IR, SEM, TEM and XRD.After the investigation of KR and racemization of (S)-1-phenylethanol, the cou-pling process of Novozym 435 and racemization catalyst about aromatic secondary alcohols was discussed. First of all, the DKR of rac-l-phenylethanol was successful constructed. High conversion (>99%) and eep (>99%) were achieved with vinyl val-erate as acyl donor catalyzed by Purolite (?) CT151 and sulfonated sepiolite. The reac-tion rate measured for the microwave irradiated DKR was approximately 1.5-3 fold that observed for the conventional heated system. High conversion (>99%) and eep (>99%) were obtained with 4-chlorophenyl valerate as acyl donor catalyzed by TiO2/SO42- and ZrO2/SO42-. The reaction rate of DKR could be enhanced by 1.2-8 fold over classical heating. Next broad substrate adaptivity and good reusability were achieved in the DKR catalyzed by the four racemization catalysts. High conversion and good eep were obtained and DKR of aromatic secondary alcohols under micro-wave irradiation showed competitive reaction rate.