143969-34-0Relevant articles and documents
Hydroboration of Alkenes Catalysed by a Nickel N-Heterocyclic Carbene Complex: Reaction and Mechanistic Aspects
Chetcuti, Michael J.,Cornaton, Yann,Djukic, Jean-Pierre,Ritleng, Vincent,Ulm, Franck
, (2020/07/13)
The pentamethylcyclopentadienyl N-heterocyclic carbene nickel complex [Ni(η5-C5Me5)Cl(IMes)] (IMes=1,3-dimesitylimidazol-2-ylidene) efficiently catalyses the anti-Markovnikov hydroboration of alkenes with catecholborane in
Synthesis and structure of indenyl rhodium(I) complexes containing unsaturated phosphines: Catalyst precursors for alkene hydroboration
Garon, Christian N.,McIsaac, Daniel I.,Vogels, Christopher M.,Decken, Andreas,Williams, Ian D.,Kleeberg, Christian,Marder, Todd B.,Westcott, Stephen A.
experimental part, p. 1624 - 1631 (2009/05/30)
The indenyl compound (η5-C9H7)Rh(coe) 2 (1, coe = cis-cyclooctene) has been prepared as a thermally stable alternative to the diethylene derivative (η5-C9H 7)Rh(η2-H2CCH2)2. Compound 1 reacts with unsaturated phosphines Ph2PR (R = CHCH 2, 2; CH2CHCH2, 3; and CC-tert-Bu, 4) to give complexes of the type (η5-C9H7)Rh(Ph 2PR)2, where bonding occurs through the phosphorus atom. Addition of Ph2PCCPPh2 to 1 gave the dimer [(η5-C9H7)Rh(μ-Ph2PCCPPh 2)]2 (5). Solution and solid state data showed that these new phosphine complexes have only a moderate amount of distortion within the indenyl ring. These compounds were found to catalyse the hydroboration of vinylarenes and the first example of an internal hydroboration of diphenylvinylphosphine has been reported. The Royal Society of Chemistry 2009.
Hydroboration of vinyl arenes using SiO2-supported rhodium catalysts
Geier, Michael J.,Geier, Stephen J.,Vogels, Christopher M.,Béland, Fran?ois,Westcott, Stephen A.
experimental part, p. 477 - 481 (2009/10/01)
The metal-catalyzed hydroboration of vinyl arenes using catecholborane (HBcat) and pinacolborane (HBpin) has been examined with SiO2- supported rhodium catalysts. Reactions with simple vinyl arenes (ArCH=CH 2) and HBcat using Rh(acac
Rh(I)-catalyzed asymmetric hydrosilylation and hydroboration/oxidation reactions using berens ligand
Marques, Carolina S.,Burke, Anthony J.
experimental part, p. 4207 - 4214 (2009/04/06)
The Berens ligand 2 was used in a number of Rh(I)-catalyzed asymmetric hydrosilylations of acetophenones under standard conditions, affording the corresponding 1-arylalcohols in ees up to 65%. Some novel Rh catalysts were generated in situ from the neutral precatalyst [Rh(μ-Cl)(COD)]2 and screened in the catalytic asymmetric hydroboration/oxidation of styrenes, gave enantioselectivities of up to 62%. Copyright Taylor & Francis Group, LLC.
Synthesis, characterization, and reactivity of rhodium(I) acetylacetonato complexes containing pyridinecarboxaldimine ligands
Kanas, Diane A.,Geier, Stephen J.,Vogels, Christopher M.,Decken, Andreas,Westcott, Stephen A.
, p. 8727 - 8735 (2009/03/11)
Addition of o-C6H4NCH=NAr to Rh(coe) 2(acac) (coe = cis-cyclooctene, acac = acetylacetonato) gave several new iminopyridine rhodium(I) complexes of the type Rh(acac)(κ2- o-C6H4NCH=NAr) (1a Ar = 4-C6H4-OMe; 1b Ar = 2,6-C6H3-Me2; 1c Ar = 2,6-C 6H3-Et2; 1d Ar = 2,6-C6H 3-i-Pr2). All new rhodium complexes have been characterized by a number of physical methods, including multinuclear NMR spectroscopy and X-ray diffraction studies for 1b and 1c. Addition of CHCl 3 to 1a afforded the corresponding rhodium(III) complex trans-Rh(κ2-o-C6H4NCH=NAr)(CHCl 2)(Cl)(acac) (2). Addition of B2cat3 (cat = 1,2-O2C6H4) to 1 gave zwitterionic Rh(η6-catBcat)(κ2-o-C6H 4NCH=NAr) (3). The molecular structure of 3b has been confirmed by a single crystal X-ray diffraction study and shows that the N2Rh fragment is bound to the catBcat anion via one of the catecholato groups in a η6-fashion. These complexes have also been examined for their ability to catalyze the hydroboration of a series of vinylarenes. Reactions using catecholborane and pinacolborane seem to proceed largely through a dehydrogenative borylation mechanism to give a number of boronated products.
Metal promoted asymmetry in the 1,2-diboroethylarene synthesis: Diboration versus dihydroboration
Ramirez, Jesus,Segarra, Anna M.,Fernandez, Elena
, p. 1289 - 1294 (2007/10/03)
Metal catalysed addition of diboranes to vinylarenes produces the desired 1,2-bis(boronate)ester and mono(boronate)esters as by-products. Their relative rate is a sensitive function between the nature of the catalytic system and the electronic effects of the substrate, that influences the mechanistic steps of the catalytic cycle. However, asymmetry is only induced as moderate enantiomeric excess values, providing an enantioface differentiation, between the bis- and mono(boronate)esters. Alternatively, the method based on the catalytic asymmetric dihydroboration/oxidation of alkynes as diphenylacetylene can provide 1,2-diphenyl-1,2-ethanediol (hydrobenzoin) with a selectivity of 68% mainly as the erythro isomer.
P1 Phenethyl peptide boronic acid inhibitors of HCV NS3 protease
Priestley,De Lucca, Indawati,Ghavimi, Bahman,Erickson-Viitanen, Susan,Decicco, Carl P.
, p. 3199 - 3202 (2007/10/03)
A series of peptide boronic acids containing extended, hydrophobic P1 residues was prepared to probe the shallow, hydrophobic S1 region of HCV NS3 protease. The p-trifluoromethylphenethyl P1 substituent was identified as optimal with respect to inhibitor potency for NS3 and selectivity against elastase and chymotrypsin.
Preparation of alcohols from alkenes via the homologation of boronates with (trimethylsilyl)diazomethane
Goddard, Jean-Philippe,Le Gall, Thierry,Mioskowski, Charles
, p. 1455 - 1456 (2007/10/03)
(Matrix presented) Alkylcatecholboranes obtained from alkenes were converted to the corresponding alkylmethanols by reaction with (trimethylsilyl)diazomethane followed by oxidation and treatment with fluoride.
Enhanced regioselectivity of rhodium-catalysed alkene hydroboration in supercritical carbon dioxide
Carter, Charles A. G.,Baker, R. Thomas,Nolan, Steven P.,Tumas, William
, p. 347 - 348 (2007/10/03)
Catalysed alkene hydroboration proceeds in supercritical CO2 with several rhodium(I) complexes using tunable fluorinated ligands and shows higher regioselectivity relative to tetrahydrofuran or perfluoromethylcyclohexane.
Vinylborane formation in rhodium-catalyzed hydroboration of vinylarenes. Mechanism versus borane structure and relationship to silation
Brown, John M.,Lloyd-Jones, Guy C.
, p. 866 - 878 (2007/10/02)
Attempted catalytic hydroboration of (4-methoxyphenyl)ethene 1 with R,R-3-isopropyl-4-methyl-5-phenyl-1,3,2-oxazaborolidine 6 proceeded extremely slowly relative to the 3-methyl analog 2 derived from φ-ephedrine when diphosphinerhodium complexes were employed. With phosphine-free rhodium catalysts, especially the 4-methoxy-phenylethene complex 7, the reaction proceeded rapidly and quantitatively to give only the corresponding (E)-vinylborane 9 and 4-methoxyethylbenzene 8 in equimolar amounts. Isotopic labeling and kinetic studies demonstrated that this reaction pathway is initiated by the formation of a rhodium hydride with subsequent reversible and regiospecific H-transfer to the terminal carbon, giving an intermediate which adds the borane and then eliminates the hydrocarbon product. Further migration of the secondary borane fragment from rhodium to the β-carbon of the coordinated olefin occurs, followed by Rh-H β-elimination which produces the vinylborane product and regenerates the initial catalytic species. When the same catalytic reaction is carried out employing catecholborane in place of the oxazaborolidine, an exceedingly rapid turnover occurs. The products are again 4-methoxyethylbenzene and the (E)-vinylborane 23 but accompanied by the primary borane 24 in proportions which vary with the experimental conditions. None of the secondary borane, which is the exclusive product when pure ClRh(PPh3)3 is employed as catalyst, is formed. The product variation as a function of initial reactant concentration was fitted to a model in which the rhodium-borane intermediate in the catalytic cycle undergoes two competing reactions-β-elimination of Rh-H versus addition of a further molecule of catecholborane. The model demonstrates that a kinetic isotope effect of 3.4 operates in the β-elimination step, but none is evident in the addition of catecholborane B-D to rhodium. A similar analysis was successfully applied to the catalytic hydrosilylation of 4-methoxystyrene, with HSiEt3, again employing the phosphine-free rhodium catalyst 7; the product distribution between primary silane 29 and vinylsilane 28 was successfully predicted. The results intimate that silation (i.e., the formation of vinylsilanes under the conditions of catalytic hydrosilylation) can best be explained by a Rh-H based mechanistic model rather than the commonly assumed variant on the Chalk-Harrod catalytic cycle. They provide an explanation for the "oxygen effect" on the rate of Rh-catalyzed hydrosilylations.
