Design of tandem catalyst by co-immobilization of metal and enzyme on mesoporous foam for cascaded synthesis of (R)-phenyl ethyl acetate

Abstract

Co-operative and complex catalytic transformations in biological systems comprise a set of diverse reactions in a single compartment. Herein, palladium and Cal B lipase were sequentially co-immobilized in the microenvironment of mesocellular foam to mimic biological systems and fully characterized. At optimal conditions, complete hydrogenation of acetophenone was achieved at atmospheric hydrogen pressure. The in-situ formed racemic 1-phenyl ethanol was then kinetically resolved selectively using lipase immobilized on the same support using vinyl acetate as (R)-phenylethyl acetate. For comparison, a single pot reaction was also conducted wherein supply of hydrogen was discontinued after complete conversion of acetophenone and further kinetic resolution was carried out in nitrogen atmosphere by adding vinyl acetate to system. The reaction showed complete conversion in 10h for hydrogenation step while lipase catalyzed gave 49.11% of selectivity towards R enantiomer with respect to racemic mixture with 100% enantiomeric excess (ee). The designed tandem catalyst avoids the use of multiple supports, purification of intermediate product as well as use of multiple reactors making process green and economical.