Asymmetric alkene epoxidation by Mn(III)salen catalyst in ionic liquids

• Type: Article in International Scientific Journal
• Date: 2010

Authors

Jorge Teixeira (Author) Other; Ana Rosa Silva (Author) Other; Luis C Branco (Author) Other; Carlos A M Afonso (Author) Other; Cristina Freire (Author) FCUP

Journal

Title: Inorganica Chimica Acta

Vol. 363

Pages: 3321-3329

ISSN: 0020-1693

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 14 Citations

Scopus - 17 Citations

Scientific classification

FOS: Natural sciences > Chemical sciences

Other information

Authenticus ID: P-003-1TJ

DOI: 10.1016/j.ica.2010.06.018

Abstract (EN): The enantioselective epoxidation of 6-cyano-2,2-dimethylchromene (Chrom) catalysed by the Jacobsen catalyst, using sodium hypochlorite (NaOCl) as oxygen source, at room temperature, was performed in a series of 1,3-dialkylimidazolium and tetra-alkyl-dimethylguanidium based ionic liquids. All the room temperature ionic liquids (RTILs) could be used as reaction media for the enantioselective epoxidation of the alkene giving, generally, moderate to good epoxide yields and enantiomeric excesses (ee%). For the series of ionic liquids derived from the 1,3-dialkylimidazolium cation, it was observed some relationship between the RTILs physical properties and the catalytic reaction parameters, exemplified by linear correlations between (i) the ee% and the alpha Kamlet-Taft parameter (hydrogen bond acidity of the solvent) for CH(2)Cl(2) and [C(4)m(n)im][BF(4)] ionic liquids (n = 1 or 2), and (ii) the ee% and the beta Kamlet-Taft parameter (hydrogen bond basicity of the solvent) for CH(2)Cl(2) and [C(4)mim][X] ionic liquids (X = PF(6), NTf(2) or BF(4)). All the RTILs could be reused in further catalytic cycles, with the exception of [C(8)mim][PF(6)]. The reutilisation of the Jacobsen catalyst for four times generally led to a decrease in the epoxide yield and to a slight decrease in the enantioselectivity. The recycling of the catalyst could be improved by imparting an ionic character to the complex through abstraction of the axially coordinated chloride anion (Cat 2). Other oxygen sources, such as iodosylbenzene, hydrogen peroxide and urea-hydrogen peroxide adduct, were also tested coupled with Jacobsen catalyst, but the best results were achieved with NaOCl.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9