Design of tandem catalyst by co-immobilization of metal and enzyme on mesoporous foam for cascaded synthesis of (R)-phenyl ethyl acetate Prof G. D. Yadav, a * Deepali Magadum, a a Department of chemical Engineering, Institute of Chemical Technology, Nathalal Parekh Marg, Matunga, Mumbai- 400019, INDIA. *Corresponding author: Fax: (+) 022-33611020 E-mail: gdyadav@yahoo.com; gd.yadav@ictmumbai.edu.in Abstract: Herein, palladium and Cal B lipase were sequentially co-immobilized in the microenvironment of mesocellular foam to mimic biological systems and fully characterized. 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. The reaction showed complete conversion in 10 h 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. Keywords: Tandem catalysis; Cascade reactions; Enantio-selectivity 1. Introduction A broad range of catalytic reactions using esterases, alcohol dehydrogenases or lipases in combination with encapsulated gold or ruthenium complexes were used for cascade reactions 1 . Lang et al. constructed novel sequential biosensors by co-immobilizing glucoamylase and glucose oxidase for detection of starch with a limit of 0.003% (w/w) 2 . Gustafsson et al. co-immobilized glucose oxidase and horse radish peroxidase on silica support in a spatially controlled way in association with poly-cationic dendridomers polymer 3 . Co-porphyrin and HNTf2incore and Rh-TsDPEN in shell type of catalyst was used for hydration of terminal alkynes followed by Rh-catalyzed asymmetric transfer hydrogenation in the shell 4 . Dynamic kinetic resolution of racemic alcohols using supramolecular-cluster lipase was demonstrated using oxo- vanadium as a racemizing co-catalyst inside mesoporous silica 5 . Backvall et al. successfully supported palladium and lipase on the single support wherein palladium efficiently racemized primary amines and the dynamic kinetic resolution was catalyzed by lipase 6 .The foregoing suggests that there is a great scope for co- immobilization of different moieties, particularly chemical and enzymatic sites on a suitable support can be used in industrially important reactions having chiral centers. 2. Experimental (or Theoretical) Mesocellular foam (MCF) was synthesized by using TEOS as a source of silica. The wet impregnation method was used for the loading 8% of palladium on the surface of MCF. After loading of palladium, Lipase was immobilized on the support. Catalyst characterization was performed by FTIR, SEM, surface area analyzer, XRD, ICP OES, pulse chemisorption at every stage of the process. The prepared tandem catalyst was employed for enantioselective synthesis of (R)-phenyl ethyl acetate from acetophenone as starting material. Various parameters were optimized by conducting experiments one factor at a time. 3. Results and discussion The GC analysis of the reaction proved that designed tandem catalyst successfully hydrogenated acetophenone to a racemic mixture of 1-phenyl ethanol which in turn acylated by vinyl acetate on lipase. Figure 1 showed the concentration profile of cascaded synthesis of the (R)-phenyl ethyl acetate using prepared catalyst. Table 1 represent different control experiments and their outcomes for the reaction.