title: Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)Co(III) complexes. Practical synthesis of enantioenriched terminal epoxides and 1,2-diols.
abstract: The hydrolytic kinetic resolution (HKR) of terminal epoxides catalyzed by chiral (salen)Co(III) complex 1 x OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several appealing features from a practical standpoint, including the use of H(2)O as a reactant and low loadings (0.2-2.0 mol %) of a recyclable, commercially available catalyst. In addition, the HKR displays extraordinary scope, as a wide assortment of sterically and electronically varied epoxides can be resolved to > or = 99% ee. The corresponding 1,2-diols were produced in good-to-high enantiomeric excess using 0.45 equiv of H(2)O. Useful and general protocols are provided for the isolation of highly enantioenriched epoxides and diols, as well as for catalyst recovery and recycling. Selectivity factors (k(rel)) were determined for the HKR reactions by measuring the product ee at ca. 20% conversion. In nearly all cases, k(rel) values for the HKR exceed 50, and in several cases are well in excess of 200.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Schaus
authors.forename: Bridget D
authors.initials: BD
authors.lastname: Brandes
authors.forename: Jay F
authors.initials: JF
authors.lastname: Larrow
authors.forename: Makoto
authors.initials: M
authors.lastname: Tokunaga
authors.forename: Karl B
authors.initials: KB
authors.lastname: Hansen
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Gould
authors.forename: Michael E
authors.initials: ME
authors.lastname: Furrow
authors.forename: Eric N
authors.initials: EN
authors.lastname: Jacobsen
mesh_terms: D000438:Alcohols / Q000138:chemical synthesis*; D002384:Catalysis; D002614:Chelating Agents / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D005029:Ethylenediamines / Q000737:chemistry*; D006868:Hydrolysis; D007700:Kinetics; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D000438:Alcohols; D002614:Chelating Agents; D004852:Epoxy Compounds; D005029:Ethylenediamines; D003035:Cobalt; C011452:disalicylaldehyde ethylenediamine