Chemo-enzymatic Dynamic Kinetic Resolution Of Secondary Alcohols

The dynamic kinetic resolution (DKR) of aromatic alcohols has been studied in this paper. In the research, two acid resins were found not only had the catalytic ability of racemic but also had the ability of catalyze non-selective transesterification reaction of substrate with acyl donors. This side reaction in the DKR of secondary happens to be an important factor in the selectivity of DKR products. And how to suppress the side reaction just to be our primary goal.A new and efficient dynamic kinetic resolution (DKR) process of secondary aromatic alcohols by using long carbon-chain esters as acyl donors was developed. During the process, the non-selective transesterification catalyzed by CD8604 and CD550 was found to be the main reason for the decreasing of enantiomeric excess (e.e.) value. The non-selective transesterification catalyzed by acid resins with different acyl donors was found effectively suppressed while the structures of acyl donors were made complex. According to this law, we found that using complex acyl donors, such as 4-chlorophenyl valerate could effectively inhibit the resin-catalyzed transesterification, and excellent e.e. value (>99%) at high conv. (>99%) can be achieved. It is noteworthy that the system can be reused for more than 20 times without loss of conv. and e.e. value.Solid superacid Al2O3/SO42-,TiO2SO42-ZrO2/SO42- was prepared as racemization catalyst with excellent racemization capacity and also showed great potential to apply to DKR of several secondary aromatic alcohols. In the DKR ofaromatic alcohols with these three acid resins as racemization catalyst, when 4-chlorophenyl valerate was used as the acyl donor, the DKR of most secondary aromatic alcohols were achieved successfully. Most of the DKRs were achieved at>99% conversion and>99% e.e. value.