DOI: 10.1002/adsc.200700149 Noels) vs. Grubbs) Catalysts: Evidence for One Unique Active Species for Two Different Systems! Mathieu Ahr, a ChloØ Thieuleux, a, * Christophe CopØret, a Bernard Fenet, b,c and Jean-Marie Basset a, * a C2P2, UMR 5265 CNRS ESCPE Lyon, Laboratoire de Chimie OrganomØtallique de Surface, ESCPE Lyon, 43 Bd du 11 Novembre 1918, 69616 Villeurbanne Cedex, France Fax: (+ 33)- 4-7243-1795; e-mail: thieuleux@cpe.fr b Centre de RMN, UniversitØ de Lyon, 69003 Lyon, France c UniversitØ Lyon 1 Claude Bernard, ESCPE Lyon, 43, Bd du 11 Novembre 1918, 69616 Villeurbanne Cedex, France Received: March 22, 2007 Supporting information for this article is available on the WWW under http://asc.wiley-vch.de/home/. Abstract: The catalytically active propagating spe- cies involved in the self-metathesis of ethyl oleate obtained from the multi-component Noels) catalytic system {[RuCl 2 ACHTUNGTRENNUNG(p-cymene)ACHTUNGTRENNUNG(PCy 3 )] + Me 3 SiCHN 2 } are probably the same as those of the single-compo- nent well-defined Grubbs) 1st generation catalyst, [Cl 2 Ru = CHPhACHTUNGTRENNUNG(PCy 3 ) 2 ](1-Ph). In the case of the Noels) catalyst, it involves the de-coordination of p- cymene, and the redistribution of PCy 3 ligands to generate only 5–10% of [Cl 2 Ru = CHRACHTUNGTRENNUNG(PCy 3 ) 2 ], where R = CH À ACHTUNGTRENNUNG(CH 2 ) 6 À CH 3 (1-Oct) and R = CH À ACHTUNGTRENNUNG(CH 2 ) 6 À COOEt (1-E), while 1-Ph can generate 100% of these species. Keywords: active species; ethyl oleate; Grubbs) cat- alyst; Noels) catalyst; olefin metathesis Within the context of sustainable development, the use of fatty oils (obtained from the biomass) as raw materials appears to be an alternative to petroleum, [1] and metathesis can be used to produce key olefinic in- termediates from fatty acid esters. Recent advances in olefin metathesis, based on the Chauvin mechanism, [2] have allowed numerous well-defined catalysts to be developed, [3] and today olefin metathesis can be used to construct complex molecular assemblies. [4] While the catalysts developed by Grubbs have been studied for the metathesis of oleate derivatives, [5] no data have been reported on the cheaper Noels) type cata- lyst, [6] which is generated in situ by reacting [RuCl 2 ACHTUNGTRENNUNG(p- cymene)ACHTUNGTRENNUNG(PCy 3 )] or a mixture of [RuCl 2 ACHTUNGTRENNUNG(p-cymene)] 2 dimer and PCy 3 with a carbene initiator such as (tri- methylsilyl)diazomethane (TMSD). Here, we have in- vestigated in detail this catalytic system in the self- metathesis of ethyl oleate (EO) (ratio of Ru, initiatior and PCy 3 , effect of temperature and solvents) and shown that [Cl 2 Ru = CHRACHTUNGTRENNUNG(PCy 3 ) 2 ], the Grubbs) 1st generation catalyst (1-Ph, Grubbs I), [7] is in fact gen- erated in situ. First, using the experimental conditions reported by Noels et al. for the ROMP of cycloolefins {[RuCl 2 ACHTUNGTRENNUNG(p- cymene)ACHTUNGTRENNUNG(PCy 3 )] 1 mol%, 60 8C, in chlorobenzene in the presence of an excess of TMSD (12 equivs.)}, only 10% of EO is converted after 24 h (Table 1, entry 1). Note that the use of [RuCl 2 ACHTUNGTRENNUNG(p-cymene)] 2 in the ab- sence of PCy 3 gives only poor conversion (ca. 1% after 24 h, entry 2) in contrast to what is observed in ROMP of norbornene and norbornadiene esters, which can be performed without PCy 3 . [6e] In fact, in- creasing the amount of PCy 3 to 2 equivs. per Ru im- proves slightly the conversion of EO to 27% (entry 3). Second, the effect of the amount of initiator (TMSD), typically used in excess (2–7 equivs./Ru), was tested. [6b] Decreasing the amount from 12 to 4 to 1 equiv. increased the conversion at 24 h from 10 to 32 to 34%, respectively (entries 1 vs. 4 and 5). How- ever, further decreasing the amount of TMSD is detri- mental, and the conversions decreased from 25% to 3% when the amount of TMSD decreased from 0.5 to 0 equiv. (entries 5 vs. 6 and 7). Thus, the addition of a stoichiometric amount of TMSD per [RuCl 2 ACHTUNGTRENNUNG(p- cymene)ACHTUNGTRENNUNG(PCy 3 )] is better for good conversions. Third, the reaction can be run between 25 and 60 8C without major influence on the conversion (33–34%) after 24 h, while higher temperatures, e.g., 80 8C, destroy the catalyst (conversion of EO reaches 13% and stops after 2 h, in agreement with a deactivation of the catalyst; entries 5 vs. 8 and 9). Finally, while the reaction cannot be run in neat EO, concentrations varying between 0.5 and 2.0M can be used. It is also possible to replace chloroben- Adv. Synth. Catal. 2007, 349, 1587–1591 # 2007 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 1587 COMMUNICATIONS