Dynamic kinetic resolution of amines by using palladium nanoparticles confined inside the cages of amine-modified MIL-101 and lipase

Abstract Dynamic kinetic resolution (DKR) of amines is an important strategy for the synthesis of chiral drugs and their building blocks; however, improving the matchability of metal-catalyzed racemization and enzymatic resolution is still a task. In this paper, Pd nanoparticles (NPs) were encapsulated inside the cages of ethylenediamine-grafted MIL-101 (ED-MIL-101), giving highly efficient catalysts (Pd/ED-MIL-101) for the racemization of primary amines. The racemization can be combined with lipase-catalyzed resolution in a one-pot DKR of rac -1-phenylethylamine leading to optically pure product (>99% ee value) with an excellent conversion and selectivity up to 99% and 93%, respectively, superior to other catalysts, such as Pd/MIL-101, Pd/MCM-41 and commercially available Pd/C. Furthermore, the heterogeneous chemoenzymatic catalyst combination can be recovered and recycled 8 times without significant loss of efficiency. The enhance catalytic performances were found to depend on the amine modification of MIL-101 that not only endows the surface of its cages with basic property, but also enables efficiently confining Pd NPs in the cages. In addition, the matchability of such chemoenzymatic catalyst combination can be further enhanced by conducting the DKR process under microwave irradiation.