3239-03-0Relevant articles and documents
Heterogeneous Hydroxyl-Directed Hydrogenation: Control of Diastereoselectivity through Bimetallic Surface Composition
Shumski, Alexander J.,Swann, William A.,Escorcia, Nicole J.,Li, Christina W.
, p. 6128 - 6134 (2021/05/29)
Directed hydrogenation, in which product selectivity is dictated by the binding of an ancillary directing group on the substrate to the catalyst, is typically catalyzed by homogeneous Rh and Ir complexes. No heterogeneous catalyst has been able to achieve equivalently high directivity due to a lack of control over substrate binding orientation at the catalyst surface. In this work, we demonstrate that Pd-Cu bimetallic nanoparticles with both Pd and Cu atoms distributed across the surface are capable of high conversion and diastereoselectivity in the hydroxyl-directed hydrogenation reaction of terpinen-4-ol. We postulate that the OH directing group adsorbs to the more oxophilic Cu atom while the olefin and hydrogen bind to adjacent Pd atoms, thus enabling selective delivery of hydrogen to the olefin from the same face as the directing group with a 16:1 diastereomeric ratio.
Disilaruthena- and Ferracyclic Complexes Containing Isocyanide Ligands as Effective Catalysts for Hydrogenation of Unfunctionalized Sterically Hindered Alkenes
Sunada, Yusuke,Ogushi, Hajime,Yamamoto, Taiji,Uto, Shoko,Sawano, Mina,Tahara, Atsushi,Tanaka, Hiromasa,Shiota, Yoshihito,Yoshizawa, Kazunari,Nagashima, Hideo
, p. 4119 - 4134 (2018/03/29)
Disilaferra- and disilaruthenacyclic complexes containing mesityl isocyanide as a ligand, 3′ and 4′, were synthesized and characterized by spectroscopy and crystallography. Both 3′ and 4′ showed excellent catalytic activity for the hydrogenation of alkenes. Compared with iron and ruthenium carbonyl analogues, 1′ and 2′, the isocyanide complexes 3′ and 4′ were more robust under the hydrogenation conditions, and were still active even at higher temperatures (～80 °C) under high hydrogen pressure (～20 atm). The iron complex 3′ exhibited the highest catalytic activity toward hydrogenation of mono-, di-, tri-, and tetrasubstituted alkenes among currently reported iron catalysts. Ruthenium complex 4′ catalyzed hydrogenation under very mild conditions, such as room temperature and 1 atm of H2. The remarkably high catalytic activity of 4′ for hydrogenation of unfunctionalized tetrasubstituted alkenes was especially notable, because it was comparable to the activity of iridium complexes reported by Crabtree and Pfaltz, which are catalysts with the highest activity in the literature. DFT calculations suggested two plausible catalytic cycles, both of which involved activation of H2 assisted by the metal-silicon bond through σ-bond metathesis of late transition metals (oxidative hydrogen migration). The linear structure of M C≡N - C (ipso carbon of the mesityl group) played an essential role in the efficient hydrogenation of sterically hindered tetrasubstituted alkenes.
Palladium on graphene: The in situ generation of a catalyst for the chemoselective reduction of α,β-unsaturated carbonyl compounds
Morimoto, Naoki,Yamamoto, Shun-Ichi,Takeuchi, Yasuo,Nishina, Yuta
, p. 15608 - 15612 (2013/09/12)
Palladium-supported graphene oxide has been successfully applied as a catalyst precursor for the selective reduction of α,β-unsaturated carbonyl compounds. Pd nanoparticles were formed during the course of the reduction with only negligible leaching of the Pd species into the reaction mixture.
Polymer supported 2,2'-dipyridylmethane: catalytic activity of transition metal complexes in hydrogenations and oligomerizations
Moberg, Christina,Rakos, Laszlo
, p. 125 - 132 (2007/10/02)
The palladium(II) acetate complex of the chelating ligand 2,2'-dipyridylmethane supported on polystyrene-2percent divinylbenzene is an efficient catalyst for hydrogenation of alkenes and alkynes.Cyclopentadiene can be reduced with high selectivity to cyclopentene, but no selectivity is observed for the non-conjugated diene 1,5-cyclooctadiene.In the hydrogenation of 3-methylcyclohex-2-en-1-ol only small amounts of ketone are formed as a by-product, in contrast to the reaction catalysed by palladium on charcoal.Nickel(II) complexes of the same ligand catalyze the trimerization of butadiene to 1,5,9-cyclododecatrienes.
Directing Effects in Homogeneous Hydrogenation with PF6
Crabtree, Robert H.,Davis, Mark W.
, p. 2655 - 2661 (2007/10/02)
The presence of a ligating group, e.g., OH, CO2Me, C=O, or OMe, on an olefinic substrate is shown to direct the attack of the hydrogenation catalyst PF6/H2/CH2Cl2 from the face of the molecule containing the directing group.Isomerization is a minor side reaction in the cases studied.The origin of this effect is discussed and a model intermediate isolated.
PHOTOCHEMICAL TRANSFORMATIONS-IV. OXYFUNCTIONALIZATION OF SOME SATURATED HYDROCARBONS WITH HYDROXYL RADICALS
Sharma, S. N.,Sonawane, H. R.,Dev, Sukh
, p. 2483 - 2492 (2007/10/02)
It is shown that hydroxylation of saturated hydrocarbons by hydrogen peroxide occurs under the influence of light.This reaction has been investigated on acyclic, monocyclic and bicyclic hydrocarbons.These reactions were also studied using performic acid as the source of hydroxyl radicals and results compared with those obtained with peracetic acid.As expected, the preferred attack was on tertiary centres, followed by secondary and then primary.
Hydrogen Participation vs. Elimination. The Role and Fate of Neighboring Hydrogen in Solvolysis of Neomenthyl Tosylate
Hirsl-Starcevic, Sanja,Majerski, Zdenko,Sunko, Dionis E.
, p. 3388 - 3393 (2007/10/02)
Product composition and α-d1 and β-d3 isotope effects in the solvolysis of neomenthyl tosylate (8-OTs) were determined in 70 percent aqueous trifluoroethanol and 70 percent aqueous ethanol.Both trifluoroethanolysis and ethanolysis gave 1-2 percent neomenthol (97percent d3), 12-13percent cis-4-menthanol (100percent d3), 2-3percent trans-4-menthanol (100percent d3), 66-70percent 3-p-menthene (83percent d3 and 17percent d2), and 5-9percent 4,8-p-menthene (97percent d3), respectively.These results and the high value of the β-d3 isotope effect (kH/kD=2.45) were interpreted in terms of rate-determining hydride shift followed by elimination which accounts for 75percent of all products.In 85percent of the elimination productsthe migrating hydrogen (deuterium) is not the one being eliminated.
