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Synlett 2013; 24(10): 1250-1254
DOI: 10.1055/s-0033-1338877
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© Georg Thieme Verlag Stuttgart · New York

Testing New Ruthenium Complexes bearing Chiral 1,2,4-Triazol-5-ylidene ­Ligands as Catalysts for Asymmetric Olefin Metathesis

Rafał Gawin
a   Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Fax: +48(22)343-2109   eMail: klgrela@gmail.com
,
Michał Pieczykolan
a   Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Fax: +48(22)343-2109   eMail: klgrela@gmail.com
,
Maura Malińska
b   University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland
,
Krzysztof Woźniak
b   University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland
,
Karol Grela*
a   Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland   Fax: +48(22)343-2109   eMail: klgrela@gmail.com
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Publikationsverlauf

Received: 12. April 2013

Accepted after revision: 08. Mai 2013

Publikationsdatum:
28. Mai 2013 (online)

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Abstract

New ruthenium complexes bearing chiral 1,2,4-triazol-5-ylidene ligands were obtained and tested in model asymmetric metathesis reactions. Low enantioselectivity in asymmetric ring-closing metathesis (ARCM) and moderate enantioselectivity in asymmetric ring-opening/ring-closing metathesis (AROCM) was observed.

Key words

ruthenium - carbene complexes - NHC - olefin meta­thesis - asymmetric catalysis

Supporting Information

    for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
  • Supporting Information
 

  • References and Notes


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      Ruthenium carbene complexes bearing achiral 1,2,4-triazol-5-ylidene have been obtained. See:
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  • 16 Synthesis of 7d: (S)-5-sec-Butylmorpholin-3-one (13; 692 mg, 4.40 mmol) was dissolved in anhyd CH2Cl2 (10 mL) and Me3OBF4 (651 mg, 4.4 mmol) was added. The mixture was stirred at r.t. for 24 h. Pentafluorophenyl hydrazine (872 mg, 4.40 mmol) was added in one portion and the mixture was further stirred for 24 h at r.t. The solvent was evaporated and residue was dried in high vacuum. Chlorobenzene (5 mL) and triethyl orthoformate (1.8 mL, 11.0 mmol) were added and the mixture was heated to 130 °C for 24 h and then stored overnight in fridge. The precipitated crystals were filtered off and washed with toluene and dried in high vacuum to give the desired product as a white solid (1.40 g, 72%).
  • 17 AROCM of 11 with In Situ Prepared Catalyst 8d: To a solution of bis(tricyclohexylphosphine)benzylidene ruthenium dichloride (8.2 mg, 0.01 mmol, 5 mol%) in anhyd THF (0.5 mL) silver complex 15 (6.2 mg, 0.007 mmol, 3.5 mol%) was added under argon and the reaction mixture was stirred at r.t. for 15 min. After that time the reaction mixture was transferred to a solution of 11 (32.8 mg, 0.2 mmol) and styrene (104.2 mg, 1.0 mmol) in anhyd THF (0.5 mL) and the formed mixture was stirred at 24 °C for 24 h under an argon atmosphere. The reaction was quenched by addition of ethyl vinyl ether and the reaction mixture was concentrated under vacuum. Conversion was determined by 1H NMR while the ee value was determined by HPLC analysis using a chiral column (Daicel Chiralcel® OJ).