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    Copper-Catalysed Allylic Substitution Using 2,8,14,20-Tetrapentylresorcinarenyl-Substituted Imidazolium Salts
    (Wiley-V C H Verlag Gmbh, 2015) Kaloglu, Murat; Sahin, Neslihan; Semeril, David; Brenner, Eric; Matt, Dominique; Ozdemir, Ismail; Kaya, Cemal
    Unsymmetrical imidazolium salts, each having one nitrogen atom (N1) substituted by a cavity-shaped TPR group (TPR = 2,8,14,20-tetrapentylresorcinaren-5-yl), were tested in situ as proligands for the copper-catalysed allylic arylation of cinnamyl bromide with arylmagnesium halides. The catalytic systems produced mixtures of linear (l) and branched (b) arylated compounds in variable proportions, with the b/l ratio being the highest (78:22) for the most crowded imidazolium salt used, namely that in which the second nitrogen atom (N2) was substituted by a mesityl group. An N-heterocyclic carbene complex obtained from one of the imidazolium salts was characterised by an X-ray diffraction study.
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    The Influence of Imidazolylidene Ligands with Bulky Resorcinarenyl Substituents on Catalysts for Suzuki-Miyaura Coupling
    (Wiley-V C H Verlag Gmbh, 2016) Kaloglu, Murat; Semeril, David; Brenner, Eric; Matt, Dominique; Ozdemir, Ismail; Toupet, Loic
    PEPPSI-type imidazolylidene palladium complexes having their carbenic ring N-substituted with an aryl ring and a cavity-shaped unit [25,26,27,28-tetrapropyloxycalix[4]aren-5-yl or 6(10),12(16),18(22)-tetramethylenedioxy-2,8,14,20-tetrapentylresorcin[4]aren-5-yl (TPR)] have been prepared and assessed in Suzuki-Miyaura cross-couplings. Remarkable efficiency in the coupling of aryl chlorides with sterically hindered arylboronic acids was observed for the carbene ligand having its N atoms (N1, N2) substituted by a mesityl and a TPR group, respectively. This good performance possibly arises from strong steric interactions between the pentyl-substituted cavitand unit and the catalytic centre, which favours reductive elimination. Two of the imidazolium salts used for complex synthesis were characterised by X-ray diffraction analysis.
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    Resorcinarene-Functionalised Imidazolium Salts as Ligand Precursors for Palladium-Catalysed SuzukiMiyaura Cross-Couplings
    (Wiley-V C H Verlag Gmbh, 2013) Sahin, Neslihan; Semeril, David; Brenner, Eric; Matt, Dominique; Ozdemir, Ismail; Kaya, Cemal; Toupet, Loic
    Three imidazolium salts based on a rigid resorcinarene platform (13) were synthesised and used as catalyst precursors in the SuzukiMiyaura cross-coupling of aryl halides with phenylboronic acid. In these pro-carbene ligands, the heterocyclic moiety has one N atom connected to a C2 atom of a resorcinolic ring, and the other is substituted by an alkyl group (R=n-propyl, iso-propyl, benzyl). The methinic C atoms of the macrocyclic core are all substituted by a pentyl group. The best catalytic performances were obtained by using an imidazolium/Pd ratio of 1:1. The catalytic systems displayed high activities, which increased in the order R=n-propyl(1)
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    Subtle Steric Effects in Nickel-Catalysed Kumada-Tamao-Corriu Cross-Coupling Using Resorcinarenyl-Imidazolium Salts
    (Wiley-V C H Verlag Gmbh, 2013) Sahin, Neslihan; Semeril, David; Brenner, Eric; Matt, Dominique; Ozdemir, Ismail; Kaya, Cemal; Toupet, Loic
    Three resorcinarene-cavitands bearing a 3-R-1-imidazolylium substituent (R = alkyl) grafted to the wider rim of the cavitand (1-3) were assessed in the Kumada-Tamao-Corriu cross-coupling of aryl halides with arylmagnesium halides. Their combination with [Ni(cod)(2)] (cod = 1,5-cyclooctadiene; 1:1 stoichiometry) resulted in highly efficient catalysts, the activities of which varied in the following order: R = n-propyl (1) < isopropyl (2) approximate to benzyl (3). A remarkable turnover frequency of 60400 mol(ArX) mol(Ni)(-1) h(-1) was obtained in the coupling of 2-bromo-6-methoxynaphthalene with PhMgBr (100 degrees C in dioxane, with precursor 2). The high activities of the cavitand derivatives were attributed to steric effects that facilitate the reductive-elimination/product decoordination step. Comparative experiments carried out with a structurally modified resorcinarene, as well as cavity-free imidazolium salts bearing 2-methoxyaryl substituents, suggest that the efficiency of the catalysts mainly relies on steric interactions between the metal and the flexible substituents attached to two methine carbon atoms. These steric interactions are probably reinforced each time the metal binds one of the two oxygen atoms located next to the catalytic centre.