Lipase and sulfuric acid were combined to achieve the dynamic kinetic resolution (DKR) of sec-alcohols. Concomitant use of these inherently incompatible catalysts was achieved via phase separation in a Pickering emulsion. Racemization in an acidic aqueous phase significantly suppressed the dehydrative side reactions that form alkenes and dimeric ethers, which are often encountered under DKR conditions in organic solvents.
This study reports the first chemoenzymatic dynamic kinetic resolution (DKR) of racemic sec-alcohols by simultaneously using immobilized lipase and aqueous sulfuric acid as catalysts for kinetic resolution and racemization, respectively. The nanoparticle-stabilized phase separation in a Pickering emulsion enabled the use of these inherently incompatible catalysts in a single vessel. The racemization reaction in the aqueous sulfuric acid solution significantly suppressed the dehydrative side reactions that form alkenes and dimeric ethers, which are often observed in racemization using Brønsted/Lewis acids or oxovanadium compounds in organic solvents. The efficacy of the Pickering emulsion was confirmed by the significantly lower catalytic performance in DKR without emulsification. This method achieved high yields and high optical purities in the production of a wide range of sec-alcohols.Zum Volltext