title: Minimizing side reactions in chemoenzymatic dynamic kinetic resolution: organometallic and material strategies.
abstract: Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this was observed to alter the rate and extent of oxidation of the alcohol to form ketone side products. The performance of highly active catalyst [(pentamethylcyclopentadienyl)IrCl(2)(1-benzyl,3-methyl-imidazol-2-ylidene)] was found to depend on the batch of lipase B used. The interaction between the bio- and chemo-catalysts was reduced by employing physical entrapment of the enzyme in silica using a sol-gel process. The nature of the gelation method was found to be important, with an alkaline method preferred, as an acidic method was found to initiate a further side reaction, the acid catalyzed dehydration of the secondary alcohol. The acidic gel was found to be a heterogeneous solid acid.
authors.affiliation: School of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Belfast, BT9 5AG, UK.
authors.forename: Ciara L
authors.initials: CL
authors.lastname: Pollock
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Fox
authors.forename: Sophie D
authors.initials: SD
authors.lastname: Lacroix
authors.forename: James
authors.initials: J
authors.lastname: McDonagh
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Marr
authors.forename: Alanna M
authors.initials: AM
authors.lastname: Nethercott
authors.forename: Annie
authors.initials: A
authors.lastname: Pennycook
authors.forename: Shimeng
authors.initials: S
authors.lastname: Qian
authors.forename: Linda
authors.initials: L
authors.lastname: Robinson
authors.forename: Graham C
authors.initials: GC
authors.lastname: Saunders
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Marr
mesh_terms: D002384:Catalysis; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D005782:Gels / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008049:Lipase / Q000737:chemistry / Q000378:metabolism*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010626:Phenylethyl Alcohol / Q000737:chemistry / Q000378:metabolism; D012822:Silicon Dioxide / Q000737:chemistry
chemical_list: D005656:Fungal Proteins; D005782:Gels; D009942:Organometallic Compounds; D012822:Silicon Dioxide; D006859:Hydrogen; D008049:Lipase; C431349:lipase B, Candida antarctica; D010626:Phenylethyl Alcohol