Biomedical subjects
Publications and source records attributed to Loïc Toupet.
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Two synthetic routes to Pd(I) dimers that feature a bridging 1-phenyl- and 1-cyclohexyl-2,5-di(2-pyridyl)phosphole ligand, 3 a and 3 b, respectively, are described. The first involves a conproportionation process between Pd(II) and Pd(0) complexes, while the second involves ligand displacement from a preformed Pd(I) dimer. Both routes are operable for 1-phenylphosphole 1 a, whereas the former failed with 1-cyclohexylphosphole 1 b. A mechanistic study revealed that the conproportionation pathway implies a reversible oxidative addition of the P-C(phenyl) bond of Pd(II)-coordinated 1 a to Pd(0) leading to a bimetallic Pd(II) complex 5. The structures of complexes 3 a and 3 b were studied by means of X-ray diffraction. The similarity of these solid-state structures suggests that the bridging mode of the P atom is due to mu-1kappaN:1,2kappaP:2kappaN coordination of ligands 1 a, b. The electrochemical behaviour and UV/Vis absorption properties of complexes 3 a, b are reported. Complex 3 a is inert towards CO, PPh(3) and 1,3-dipoles. It reacted with dimethylacetylene dicarboxylate to give complex 6 as a result of insertion of the alkyne into the Pd-Pd bond. X-ray diffraction studies of complexes 5 and 6 are also presented.
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.
The X-ray structure of [Zn(4-bromocalcimycin)2 x H2O] complex shows two highly different conformations of the ligand in the dimeric association, unusual in this ionophore family.
The development of a new strategy for the synthesis of alpha-hydroxyalkyl dihydropyrans is reported. This approach is based on a tandem hetero[4+2]/allylboration reaction.
1-(Z)-Alkoxy-4-(E)-methoxybutadiene derivatives have been reacted with ethylgyoxylate and diethyl ketomalonate under thermal or hyperbaric conditions. They provide, with a total regioselectivity and fair to total endoselectivities, the expected dihydropyranic cycloadducts. Three of those pseudo-glycals have been converted in a few classical steps (deprotection, reduction, and dihydroxylation) into (racemic) allose, mannose, and gullose derivatives. The order of these three steps has a direct influence on the efficiency of the transformation and determines the stereochemistry of the final sugar.
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Explore the source record for details and available documents.