In the last decade, cooperative catalysis has received considerable attention as a powerful synthetic method. [1] Two or more catalysts function simultaneously or sequentially in a single reaction vessel to construct complicated molecules, which provides a means to perform unprecedented syntheses that cannot be achieved by a single catalyst. Various catalytic combinations involving transition metals, organocatalysts, and biocatalysts have been developed thus far. [2] A typical example is the combined use of lipases and transition metals to attain the dynamic kinetic resolution (DKR) of racemic secondary alcohols for producing single enantiomer products in up to 100 % yields, [3] in contrast to the use of lipases alone, which can only achieve maximum yields of 50 %. In this DKR process, the enzymatic enantioselective esterification of racemic alcohols is combined with the transition-metal-catalyzed continuous racemization of optically active alcohols, which remain intact during the enzymatic reaction, through a redox process. However, such cooperative cocatalysis often encounters crucial issues of low compatibility between the lipases and the transition metals. Although intense efforts have been devoted to developing highly active racemization catalysts, [4, 5] only a few ruthenium complexes have met both the requirement of sufficient compatibility with lipases and high racemization activity. [5] We recently reported that a combination of oxovanadium compounds (4 or 5) with lipases accomplished the efficient and direct conversion of racemic allylic alcohols (AE)-1 and (AE)-2 into optically active allyl esters (R)-3. [6] This method featured a unique racemization process wherein 4 (or 5) catalyzed the racemization of (S)-1 with 1,3-transposition of the hydroxy group of 1 or 2, while the lipases effected chemoand enantioselective esterification. This is significantly different from the above-mentioned ruthenium-catalyzed DKRs and offered a synthetic advantage in that both (AE)-1 and (AE)-2 were available as equivalent substrates. However, this method required further improvement in both catalytic activity and compatibility of the oxovanadium catalysts with the lipases. [7,8] Herein, we report the preparation of a novel oxovanadium catalyst (V-MPS) immobilized inside mesoporous silica (MPS) with pores of approximately 3 nm in diameter, which enabled a complete division of the racemization site and the enzymatic reaction site. The combined lipase-V-MPS catalyst is reusable and achieved DKR of a wide range of racemic alcohols with excellent chemical and optical yields (Scheme 1).The immobilization of oxovanadium species inside a solid carrier with microsized pores or multilayered structures [9] enables the minimization of interactions between the oxovanadium species and lipases while maintaining easy access of substrate molecules to the metal center. The solid carrier should be neutral and non-charged in order to exert little adverse effect on the lipases. Among the various potential solid carriers, [10,11] MPS,...
