Cyclooctene

Abstract: Le dioxo(tetramesitylporphyrinato) ruthenium(VI) catalyse l'epoxydation des olefines (cyclooctene, cis- et trans-β-methylstyrene, norbornene) a temperature et pression ambiantes

Abstract: A new class of sterically hindered dendrimer-metalloporphyrins was synthesized for use as shape-selective oxidation catalysts. A series of oxidatively robust poly(phenylesters) dendrimers were prepared through a convergent synthesis. Monodendrons were appended to the meta-positions of the 5,10,15,20-tetrakis(3‘,5‘-hydroxyphenyl)porphinatomanganese(III) chloride to obtain a sterically protected metal center. These complexes have been examined as regioselective oxidation catalysts for both intra- and intermolecular cases. Epoxidation of nonconjugated dienes and alkene mixtures of 1-alkene and cyclooctene catalyzed by dendrimer-metalloporphyrins has been carried out using iodosylbenzene as the oxygen donor. Significantly greater regioselectivity is observed with the dendrimer-metalloporphyrins, relative to the corresponding parent, 5,10,15,20-tetraphenylporphyrinatomanganese(III) cation. To examine the extent of steric crowding around the porphyrin from the dendrimers, molecular modeling studies were perform...

Abstract: Refluxing mixed solutions of palladium(II) chloride and hexachloroplatinic(IV) acid in ethanol–water (1 : 1, v/v) in the presence of poly(N-vinyl-2-pyrrolidone) results in well dispersed and stable colloidal dispersions of polymer-protected palladium/platinum bimetallic clusters. The UV–VIS absorption spectra and transmission electron micrographs indicate that these bimetallic cluster particles are homogeneous in size, each particle containing both palladium and platinum atoms. Dispersions of these bimetallic clusters were used as catalysts for the selective hydrogenation of cycloocta-1,3-diene to cyclooctene at 30 °C under hydrogen gas at atmospheric pressure. The catalytic activity for the partial hydrogenation was found to depend on the metal composition of the particles. A bimetallic cluster with a mole ratio of Pd : Pt = 4 : 1 was the most active catalyst, twice as active as a typical colloidal palladium catalyst, for the diene hydrogenation. The dependence of the activity and the selectivity on the surface structure of the cluster particle strongly indicates that the cluster particle with the highest catalytic activity had a ‘Pd-surrounded Pt core’ structure.

Abstract: The novel P–C–P pincer complex, [IrH2{C6H3(CH22PBut2)2}] has long-term stability and 200 ° C and catalyses the transfer dehydrogenation of cyclooctnane to cyclooctene at the rate of 12 turnovers min1 min–1.

Abstract: Computation was used to design a trans-cyclooctene derivative that displays enhanced reactivity in the tetrazine-trans-cycloctene ligation. The optimized derivative is an (E)-bicyclo[6.1.0]non-4-ene with a cis-ring fusion, in which the eight-membered ring is forced to adopt a highly strained 'half-chair' conformation. Toward 3,6-dipyridyl-s-tetrazine in MeOH at 25 °C, the strained derivative is 19 and 27 times more reactive than the parent trans-cyclooctene and 4E-cyclooct-4-enol, respectively. Toward 3,6-diphenyl-s-tetrazine in MeOH at 25 °C, the strained derivative is 160 times more reactive than the parent trans-cyclooctene.