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Cooperative Catalysis in the Hydrolytic Kinetic Resolution of Epoxides by Chiral [(salen)Co(III)] Complexes Immobilized on Gold Colloids
Author(s) -
Belser Thomas,
Jacobsen Eric N.
Publication year - 2008
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200800028
Subject(s) - chemistry , kinetic resolution , catalysis , hydrolysis , reactivity (psychology) , metal salen complexes , monomer , enantioselective synthesis , colloid , ligand (biochemistry) , monolayer , polymer chemistry , heterogeneous catalysis , organic chemistry , combinatorial chemistry , inorganic chemistry , medicine , biochemistry , polymer , alternative medicine , receptor , pathology
Chiral salen ligands were incorporated into self‐assembled thiolate monolayers (SAMs) on gold colloids. Treatment of the immobilized ligand with Co(OAc) 2 ⋅4 H 2 O yielded the corresponding [(salen)Co(II)] complex, and aerobic oxidation in the presence of triflic acid afforded the catalytically active [(salen)Co(III)] complex. Functionalized gold colloids with a diameter of 3.4 nm, coated with a mixed monolayer of n ‐octanethiolates and thiolates with chiral [(salen)Co(III)] end groups were studied as catalysts in the hydrolytic kinetic resolution (HKR) of hexene‐1‐oxide. Extremely high selectivitiy and significant rate acceleration relative to homogeneous monomeric catalysts were observed. Recovery of the immobilized catalyst was accomplished by simple filtration, and catalyst reoxidation and repeated recycling (seven times) was possible with no loss of reactivity or enantioselectivity.