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Cetinkaya B Demir S Ozdemir I Toupet L Sémeril D Bruneau C Dixneuf PH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(10):2323-2330
The reaction of electron-rich carbene-precursor olefins containing two imidazolinylidene moieties [(2,4,6-Me(3)C(6)H(2)CH(2))NCH(2)CH(2)N(R)Cdbond;](2) (2a: R=CH(2)CH(2)OMe, 2 b R=CH(2)Mes), bearing at least one 2,4,6-trimethylbenzyl (R=CH(2)Mes) group on the nitrogen atom, with [RuCl(2)(arene)](2) (arene=p-cymene, hexamethylbenzene) selectively leads to two types of complexes. The cleavage of the chloride bridges occurs first to yield the expected (carbene) (arene)ruthenium(II) complex 3. Then a further arene displacement reaction takes place to give the chelated eta(6)-mesityl,eta(1)-carbene-ruthenium complexes 4 and 5. An analogous eta(6)-arene,eta(1)-carbene complex with a benzimidazole frame 6 was isolated from an in situ reaction between [RuCl(2)(p-cymene)](2), the corresponding benzimidazolium salt and cesium carbonate. On heating, the RuCl(2)(imidazolinylidene) (p-cymene) complex 8, with p-methoxybenzyl pendent groups attached to the N atoms, leads to intramolecular p-cymene displacement and to the chelated eta(6)-arene,eta(1)-carbene complex 9. On reaction with AgOTf and the propargylic alcohol HCtbond;CCPh(2)OH, compounds 4-6 were transformed into the corresponding ruthenium allenylidene intermediates (4-->10, 5-->11, 6-->12). The in situ generated intermediates 10-12 were found to be active and selective catalysts for ring-closing metathesis (RCM) or cycloisomerisation reactions depending on the nature of the 1,6-dienes. Two complexes [RuCl(2)[eta(1)-CN(CH(2)C(6)H(2)Me(3)-2,4,6)CH(2)CH(2)N- (CH(2)CH(2)OMe)](C(6)Me(6))] 3 with a monodentate carbene ligand and [RuCl(2)[eta(1)-CN[CH(2)(eta(6)-C(6)H(2)Me(3)-2,4,6)]CH(2)CH(2)N-(CH(2)C(6)H(2)Me(3)-2,4,6)]] 5 with a chelating carbene-arene ligand were characterised by X-ray crystallography. 相似文献
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1,2‐N‐Migration in a Gold‐Catalysed Synthesis of Functionalised Indenes by the 1,1‐Carboalkoxylation of Ynamides
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Holly V. Adcock Dr. Thomas Langer Dr. Paul W. Davies 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7262-7266
Unique α‐hemiaminal ether gold carbene intermediates were accessed by a gold‐catalysed 1,1‐carboalkoxylation strategy and evolved through a highly selective 1,2‐N‐migration. This skeletal rearrangement gave functionalised indenes, and isotopic labelling confirmed the rare C?N bond cleavage of the ynamide moiety. The effect of substituents on the migration has been explored, and a model is proposed to rationalise the observed selectivity. 相似文献
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Vito VeceKhadija Ben Hadj Hassen Sylvain Antoniotti Elisabet Duñach 《Tetrahedron letters》2012,53(38):5102-5105
We described herein a Sn(NTf2)4-catalysed cyclisation of gem-(dialkoxymethyl)-1,6-dienes and derivatives where cyclohexane or tetrahydrofuran rings are formed following either a 6-enexo-endo-trig process or a 5-exo-trig process, respectively, depending on substitution patterns. The latter process features an unusual dealkylative ether cyclisation, triggered by the strong Lewis acid character of the tin(IV) triflimidate catalyst. 相似文献
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Ariadna Fuente‐Hernàndez Philippe Costes Philippe Kalck Ulises Jáuregui‐Haza Odile Dechy‐Cabaret Martine Urrutigoïty 《应用有机金属化学》2011,25(11):815-819
The CO‐bubbling effect in cycloisomerization reactions of enynes derived from monoterpenes has been studied using PtCl2, [Rh2Cl2(CO)4] and AuCl3 as catalytic systems. All the precursors are efficient catalysts for the cycloisomerization of O‐tethered enynes. The reaction proceeds through exo‐dig and endo‐dig pathways, which are consistent with the exclusive coordination of the alkyne triple bond to the metal center. The CO ligand not only increases the reaction rates but also induces significant variations in the two reaction pathways. Notably, this effect is also strongly dependent on the nature of the starting enyne. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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