The Best Performance of the Combined CAL-B/VOSO4 System Depending on the Good Mutual Coordination of Reactions

Abstract

Enantiomerically pure secondary alcohols were prepared in the combined CAL-B/VOSO4 system in one-pot conditions. Under the optimum conditions, the conversion, enantiomeric excess, selectivity and enantioselectivity reached 92%, >99%, 99% and >200 respectively. The significant improvement of the system performance should be attributed to the mutual coordination of reactions in a chemoenzymatic dynamic kinetic resolution system and reduction of by-reaction. In conclusion, our experimental data and literature data confirm that there must be an optimal amount of V-MPS (VOSO4) to coordinate the in-situ racemic reaction with the kinetic resolution reaction with which the enantiomer required is produced and the adverse kinetic resolution reaction producing adverse enantiomer and minimize the rate of the side reaction in which the substrate was consumed and the selectivity was reduced, resulting in an optimal DKR system. Considering the large activation energy of the in-situ racemic reaction and at least 76% excess catalytic capacity of VOSO4, the strategy adopted is to greatly reduce the amount of VOSO4, and thus an optimal reaction condition should be established, making the DKR system optimal.