- Efficient preparation and application of monodisperse palladium loaded graphene oxide as a reusable and effective heterogeneous catalyst for suzuki cross-coupling reaction
-
A homogeneously dispersed graphene oxide supported palladium nanomaterial (Pd?GO) has been successfully synthesized and used as a catalyst in cross-coupling reactions at room temperature. Various analytical techniques such as X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) were used to characterize the monodisperse Pd?GO. Monodisperse Pd?GO nanomaterials were used for the cross-coupling reactions which brought together organic molecules with functional significance. This catalyst showed superior catalytic activity and stability for these coupling reactions. High product yields, short reaction times and mild reaction conditions, obtained by the using of developed catalysts. Importantly, the catalyst can be used at least five experiments successfully without losing its efficiency.
- Diler, Fatma,Burhan, Hakan,Genc, Hayriye,Kuyuldar, Esra,Zengin, Mustafa,Cellat, Kemal,Sen, Fatih
-
-
- Ruthenium nanoparticle-intercalated montmorillonite clay for solvent-free alkene hydrogenation reaction
-
Well-characterized, ruthenium nanoparticle-intercalated montmorillonite clay was used as a catalyst in solvent-free alkene hydrogenation reactions and the corresponding products were obtained in good yields. The catalytic activity of ruthenium nanoparticle-intercalated montmorillonite clay was successfully tested with 16 different functionalized and non-functionalized alkenes. Apart from alkene reduction, the ruthenium nanoparticle-intercalated montmorillonite clay was also tested in Wittig-type reactions for obtaining dehydrobrittonin A, an important intermediate for the synthesis of brittonin A. Ruthenium nanoparticle-intercalated montmorillonite clay was found to be active in the synthesis of dehydrobrittonin A and brittonin A. The ability to recycle the catalyst nine times, together with low catalyst loading, high catalytic activity and catalytic selectivity were noteworthy advantages of the proposed protocol.
- Upadhyay, Praveenkumar,Srivastava, Vivek
-
p. 740 - 745
(2015/02/05)
-
- Bis(phosphine)cobalt dialkyl complexes for directed catalytic alkene hydrogenation
-
Planar, low-spin cobalt(II) dialkyl complexes bearing bidentate phosphine ligands, (P - P)Co-(CH2SiMe3)2, are active for the hydrogenation of geminal and 1,2-disubstituted alkenes. Hydrogenation of more hindered internal and endocyclic trisubstituted alkenes was achieved through hydroxyl group activation, an approach that also enables directed hydrogenations to yield contrasteric isomers of cyclic alkanes.
- Friedfeld, Max R.,Margulieux, Grant W.,Schaefer, Brian A.,Chirik, Paul J.
-
supporting information
p. 13178 - 13181
(2015/03/30)
-
- Regioselective oxidation of nonactivated alkyl C-H groups using highly structured non-heme iron catalysts
-
Selective oxidation of alkyl C-H groups constitutes one of the highest challenges in organic synthesis. In this work, we show that mononuclear iron coordination complexes Λ-[Fe(CF3SO3) 2((S,S,R)-MCPP)] (Λ-1P), Δ-[Fe(CF3SO 3)2((R,R,R)-MCPP)] (Δ-1P), Λ-[Fe(CF 3SO3)2((S,S,R)-BPBPP)] (Λ-2P), and Δ-[Fe(CF3SO3)2((R,R,R)-BPBPP)] (Δ-2P) catalyze the fast, efficient, and selective oxidation of nonactivated alkyl C-H groups employing H2O2 as terminal oxidant. These complexes are based on tetradentate N-based ligands and contain iron centers embedded in highly structured coordination sites defined by two bulky 4,5-pinenopyridine donor ligands, a chiral diamine ligand backbone, and chirality at the metal (Λ or Δ). X-ray diffraction analysis shows that in Λ-1P and Λ-2P the pinene rings create cavity-like structures that isolate the iron site. The efficiency and regioselectivity in catalytic C-H oxidation reactions of these structurally rich complexes has been compared with those of Λ-[Fe(CF3SO3) 2((S,S)-MCP)] (Λ-1), Λ-[Fe(CF3SO 3)2((S,S)-BPBP)] (Λ-2), Δ-[Fe(CF 3SO3)2((R,R)-BPBP)] (Δ-2), Λ-[Fe(CH3CN)2((S,S)-BPBP)](SbF6) 2 (Λ-2SbF6), and Δ-[Fe(CH3CN) 2((R,R)-BPBP)](SbF6)2 (Δ-2SbF 6), which lack the steric bulk introduced by the pinene rings. Cavity-containing complexes Λ-1P and Λ-2P exhibit enhanced activity in comparison with Δ-1P, Δ-2P, Λ-1, Λ-2, and Λ-2SbF6. The regioselectivity exhibited by catalysts Λ-1P, Λ-2P, Δ-1P, and Δ-2P in the C-H oxidation of simple organic molecules can be predicted on the basis of the innate properties of the distinct C-H groups of the substrate. However, in specific complex organic molecules where oxidation of multiple C-H sites is competitive, the highly elaborate structure of the catalysts allows modulation of C-H regioselectivity between the oxidation of tertiary and secondary C-H groups and also among multiple methylene sites, providing oxidation products in synthetically valuable yields. These selectivities complement those accomplished with structurally simpler oxidants, including non-heme iron catalysts Λ-2 and Λ-2SbF6.
- Gómez, Laura,Canta, Merceì,Font, David,Prat, Irene,Ribas, Xavi,Costas, Miquel
-
p. 1421 - 1433
(2013/03/29)
-
- An iron catalyst for oxidation of alkyl C-H bonds showing enhanced selectivity for methylenic sites
-
Many are called but few are chosen: A nonheme iron complex catalyzes the oxidation of alkyl C-H bonds by using H2O2 as the oxidant, showing an enhanced selectivity for secondary over tertiary C-H bonds (see scheme). Copyright
- Prat, Irene,Gomez, Laura,Canta, Merce,Ribas, Xavi,Costas, Miquel
-
supporting information
p. 1908 - 1913
(2013/03/14)
-
- An iron(III)-monoamidate complex catalyst for selective hydroxylation of alkane C-H bonds with hydrogen peroxide
-
Selective oxidation: The success of the title reaction (see scheme) is caused by the strong electron donation from the amidate moiety of the dpaq ligand to the iron center (dpaq=2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8- yl-acetamidate). This process facilitates the O-O bond heterolysis of the intermediate FeIIIOOH species to generate a selective oxidant without forming highly reactive hydroxyl radicals. Copyright
- Hitomi, Yutaka,Arakawa, Kengo,Funabiki, Takuzo,Kodera, Masahito
-
supporting information; experimental part
p. 3448 - 3452
(2012/06/16)
-
- Highly efficient, regioselective, and stereospecific oxidation of aliphatic C-H groups with H2O2, catalyzed by aminopyridine manganese complexes
-
Aminopyridine manganese complexes [LMnII(OTf)2] having a similar coordination topology catalyze the oxidation of unactivated aliphatic C-H groups with H2O2, demonstrating excellent efficiency (up to TON = 970), site selectivity, and stereospecificity (up to >99%).
- Ottenbacher, Roman V.,Samsonenko, Denis G.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
-
supporting information
p. 4310 - 4313
(2012/11/06)
-
- Iron(III) chloride-catalysed aerobic reduction of olefins using aqueous hydrazine at ambient temperature
-
A chemoselective reduction of olefins and acetylenes is demonstrated by employing catalytic amounts of ferric chloride hexahydrate (FeCl 3·6 H2O) and aqueous hydrazine (NH 2NH2·H2O) as hydrogen source at room temperature. The reduction is chemoselective and tolerates a variety of reducible functional groups. Unlike other metal-catalysed reduction methods, the present method employs a minimum amount of aqueous hydrazine (1.5-2 equiv.). Also, the scope of this method is demonstrated in the synthesis of ibuprofen in aqueous medium. Copyright
- Lamani, Manjunath,Ravikumara, Guralamata S.,Prabhu, Kandikere Ramaiah
-
supporting information; experimental part
p. 1437 - 1442
(2012/07/03)
-
- Selective Aliphatic C-H Oxidation
-
A composition including a complex of a metal, a tetradentate ligand, at least one ancillary ligand, and a counterion may be used for selective sp3 C—H bond oxidation. The tetradentate ligand may include a N-heterocyclic-N,N′-bis(pyridyl)-ethane-1,2-diamine group or a N,N′-bis(heterocyclic)-N,N′-bis(pyridyl)-ethane-1,2-diamine group. The composition can be used in combination with H2O2 to effect highly selective oxidations of unactivated sp3 C—H bonds over a broad range of substrates. The site of oxidation can be predicted, based on the electronic and/or steric environment of the C—H bond. In addition, the oxidation reaction does not require the presence of directing groups in the substrate.
- -
-
Page/Page column 14-15
(2011/02/18)
-
- Transfer hydrogenation of olefins catalysed by nickel nanoparticles
-
Nickel nanoparticles have been found to effectively catalyse the hydrogen-transfer reduction of a variety of non-functionalised and functionalised olefins using 2-propanol as the hydrogen donor. The heterogeneous process has been shown to be highly chemoselective for certain substrates, with all the corresponding alkanes being obtained in high yields. A synthesis of the natural dihydrostilbene brittonin A?is also reported based on the use of nickel nanoparticles.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
-
experimental part
p. 10637 - 10643
(2010/01/16)
-
- 79Br NMR spectroscopy as a practical tool for kinetic analysis
-
79Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using 1H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed. Copyright
- Chan, Si Jia,Howe, Andrew G.,Hook, James M.,Harper, Jason B.
-
experimental part
p. 342 - 347
(2010/02/27)
-
- Reduction of carbon-carbon double bonds using organocatalytically generated diimide
-
(Chemical Equation Presented) An efficient method has been developed for the reduction of carbon-carbon double bonds with diimide, catalytically generated in situ from hydrazine hydrate. The employed catalyst is prepared in one step from riboflavin (vitamin B2). Reactions are carried out in air and are a valuable alternative when metal-catalyzed hydrogenations are problematic.
- Smit, Christian,Fraaije, Marco W.,Minnaard, Adriaan J.
-
supporting information; experimental part
p. 9482 - 9485
(2009/04/06)
-
- Deacylation of esters, thioesters and amides by a naphthalene-catalysed lithiation
-
The reaction of different esters, thioesters and amides derived from pivalic, benzoic and 4-tert-butylbenzoic acids with an excess of lithium and a catalytic amount of naphthalene (8 mol%) led, after methanolysis, to the corresponding alcohols, thiols and amines, respectively, through a reductive non-hydrolytic procedure. This methodology represents a reasonable alternative to other non-reductive protocols. Georg Thieme Verlag Stuttgart.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
-
p. 309 - 314
(2007/10/03)
-
- Desilylation procedure via a naphthalene-catalysed lithiation reaction
-
The reaction of silyl protected alcohols, amines and thiols with lithium powder and a catalytic amount of naphthalene, in THF, at 0°C led, after hydrolysis, to the recovery of the free alcohols, amines and thiols in very good yields. At least a phenyl group was required in the silyl protecting group for the success of the reaction. Some polyfunctionalised starting materials have successfully been deprotected. The stereochemical outcome of the deprotection of a silylated chiral secondary alcohol has also been studied and no racemization was observed. The process has shown to be a good alternative to the acid-catalysed desilylation procedures, the latter being not useful for the deprotection of some silylated tertiary alcohols.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
-
p. 6908 - 6915
(2007/10/03)
-
- Deallyloxy- and debenzyloxycarbonylation of protected alcohols, amines and thiols via a naphthalene-catalysed lithiation reaction
-
The naphthalene-catalysed lithiation of Alloc- and Cbz-protected alcohols, amines and thiols in THF at 0°C led, after quenching with methanol, to the recovery of the free alcohols, amines and thiols in short reaction times and with very good yields. The selectivity for the removal of the Alloc- or the Cbz- group in a polyfunctionalised substrate has been studied. The selective reductive cleavage of a benzylic carbon-oxygen bond was achieved in the presence of an allylic carbon-oxygen or carbon-nitrogen bond. This method represents a great improvement in comparison with the previously reported deprotection procedures by dissolving metals, since it avoids the use of the toxic liquid ammonia and, therefore, the need to perform the reaction at low temperatures.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
-
p. 9319 - 9324
(2007/10/03)
-
- Electrocatalytic hydrogenation of organic compounds using current density gradient and sacrificial anode of nickel
-
Preparative electrocatalytic hydrogenation (ECH) of some organic compounds were performed: cyclohexene, 2-cyclohexen-1-one, benzaldehyde, acetophenone, styrene, 1,3-cyclohexadiene, trans-trans-2,4-hexadien-1-ol, citral, linalool and geraniol. H2O/MeOH (1:1), NH4OAc or NH4Cl (0.2 M) were used as solvent and supporting electrolyte. A sacrificial anode of nickel allowed the use of an undivided cell, with a cell voltage varying between 2.3 and 1.3 V, depending on the supporting electrolyte. A current density gradient was applied to diminish the time of reaction and obtain a good electrochemical efficiency. An in situ prepared cathode of nickel deposited on iron provided a highly efficient ECH process, and the constant deposition of nickel on the electrode surface avoided catalyst poisoning. The ECH system was somewhat selective, hydrogenating conjugated olefins in good yield.
- Santana, Diogo S.,Lima, Márcio V. F.,Daniel, Jorge R. R.,Navarro, Marcelo
-
p. 4725 - 4727
(2007/10/03)
-
- Hydrogenation on granular palladium-containing catalysts: I. Hydrogenation of tertiary acetylene alcohols
-
Commercial granular palladium catalyst (0.5% of Pd on γ-Al 2O3) was modified by treating with zinc acetate (type 1) or successively with zinc acetate and ammonia (type 2). The treatment significantly increased the hydrogenation selectivity for a triple bond into a double bond: to 85.3-93.1% with the type 1 catalyst and to 96.3-97.8% with the type 2 catalyst. A construction of an autoclave with a fixed bed of the granular catalyst is described.
- Tolkacheva,Kislyi,Taits,Semenov
-
p. 150 - 152
(2007/10/03)
-
- Highly enantiospecific oxyfunctionalization of nonactivated hydrocarbon sites by perfluoro-cis-2-n-butyl-3-n-propyloxaziridine
-
(equation presented) Nonactivated hydrocarbon sites of enantiopure compounds are oxyfunclionalized enantiospecifically by perfluoro-cis-2-n-butyl-3-n-propyloxaziridine under remarkably mild reaction conditions. The reaction occurs with retention of configuration at the oxidized stereogenic center, and the enantiospecificity is highly independent from both the carbon framework of the substrate and the presence of functional groups.
- Arnone, Alberto,Foletto, Stefania,Metrangolo, Pierangelo,Pregnolato, Massimo,Resnati, Giuseppe
-
p. 281 - 284
(2008/02/14)
-
- A refined method for the removal of the methoxymethyl (MOM) protecting group for carbinols with acidic ion-exchange resin
-
The methoxymethyl protecting group for carbinols is best removed from acid-sensitive substrates by hydrolysis in aqueous methanol using a cationic exchange resin (Dowex-50W).
- Seto,Mander
-
p. 2823 - 2828
(2007/10/02)
-