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Fast Olefin Metathesis at Low Catalyst Loading.
Fast Olefin Metathesis at Low Catalyst Loading.
- Source :
- Chemistry - A European Journal; Oct2012, Vol. 18 Issue 40, p12845-12853, 9p
- Publication Year :
- 2012
-
Abstract
- Reactions of the Grubbs 3rd generation complexes [RuCl<subscript>2</subscript>(NHC)(Ind)(Py)] (N-heterocyclic carbene (NHC)=1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene (SIMes), 1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene (SIPr), or 1,3-bis(2,6-diisopropylphenylimidazol)-2-ylidene (IPr); Ind=3-phenylindenylid-1-ene, Py=pyridine) with 2-ethenyl- N-alkylaniline (alkyl=Me, Et) result in the formation of the new N-Grubbs-Hoveyda-type complexes 5 (NHC=SIMes, alkyl=Me), 6 (SIMes, Et), 7 (IPr, Me), 8 (SIPr, Me), and 9 (SIPr, Et) with N-chelating benzylidene ligands in yields of 50-75 %. Compared to their respective, conventional, O-Grubbs-Hoveyda complexes, the new complexes are characterized by fast catalyst activation, which translates into fast and efficient ring-closing metathesis (RCM) reactivity. Catalyst loadings of 15-150 ppm (0.0015-0.015 mol %) are sufficient for the conversion of a wide range of diolefinic substrates into the respective RCM products after 15 min at 50 °C in toluene; compounds 8 and 9 are the most catalytically active complexes. The use of complex 8 in RCM reactions enables the formation of N-protected 2,5-dihydropyrroles with turnover numbers (TONs) of up to 58 000 and turnover frequencies (TOFs) of up to 232 000 h<superscript>−1</superscript>; the use of the N-protected 1,2,3,6-tetrahydropyridines proceeds with TONs of up to 37 000 and TOFs of up to 147 000 h<superscript>−1</superscript>; and the use of the N-protected 2,3,6,7-tetrahydroazepines proceeds with TONs of up to 19 000 and TOFs of up to 76 000 h<superscript>−1</superscript>, with yields for these reactions ranging from 83-92 %. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 09476539
- Volume :
- 18
- Issue :
- 40
- Database :
- Complementary Index
- Journal :
- Chemistry - A European Journal
- Publication Type :
- Academic Journal
- Accession number :
- 80236264
- Full Text :
- https://doi.org/10.1002/chem.201201010