3597-91-9Relevant articles and documents
A new homogeneous polymer support based on syndiotactic polystyrene and its application in palladium-catalyzed Suzuki-Miyaura cross-coupling reactions
Shin, Jihoon,Bertoia, Julie,Czerwinski, Kenneth R.,Bae, Chulsung
, p. 1576 - 1580 (2009)
Soluble syndiotactic polystyrene-supported triphenylphosphine (sPS-TPP) was synthesized by reacting borylated syndiotactic polystyrene with (4-bromophenyl)diphenylphosphine. A palladium catalyst, supported on sPS-TPP, effectively catalyzed Suzuki-Miyaura coupling reactions of aryl halides under homogeneous conditions. The polymer-supported palladium complex was recovered quantitatively by adding an equal volume of poor solvent to the polymer, and coupling products could be easily isolated by evaporating the solvents. The recovered polymer complex was reused several times without significant loss of activity. The Royal Society of Chemistry 2009.
Facile Suzuki-Miyaura cross coupling using ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose
Kale, Dolly,Rashinkar, Gajanan,Kumbhar, Arjun,Salunkhe, Rajashri
, p. 9 - 16 (2017)
A novel ferrocene tethered N-heterocyclic carbene-Pd complex anchored on cellulose has been prepared by multi-step synthesis. The complex proved to be robust and efficient heterogeneous catalyst for synthesis of biaryls in Suzuki-Miyaura cross coupling reaction.
Improved aqueous Cannizzaro reaction in presence of cyclodextrin
Canipelle,Landy,Fourmentin
, p. 349 - 353 (2011)
An aqueous hydroxypropyl-β-cyclodextrin solution has been used to increase the conversion of 4-biphenylcarboxaldehyde into the corresponding alcoholic and carboxylic substrates, by means of a Cannizzaro reaction. The observed enhancement has been ascribed to a partial solubilization of 4-biphenylcarboxaldehyde. In addition, as the main part of the organic substrates still remains insoluble, synthesized products are easily recovered by filtration. As a consequence, the basic cyclodextrin solution might also be reused for a new synthetic cycle, without significant loss of conversion. Aqueous solid-liquid biphasic reaction in presence of cyclodextrins thus seems to be a promising tool in the green chemistry field.
Development of p-phenylbenzyl as a new protecting group: Protection and deprotection of alcohols
Sharma,Rakesh
, p. 5571 - 5573 (2001)
p-Phenylbenzyl is developed as a new 'PMB' like protecting group. p-Phenylbenzyl (PPB) ethers were prepared from alcohols with PPBBr-NaH or p-phenylbenzyl trichloroacetimidate-TfOH and subjected to oxidative deprotection using DDQ or DDQ (10 mol%)-3 equiv. Mn(OAc)3.
Target alcohol/phenol release by cyclative cleavage using glycine as a safety catch linker.
Raghavan, Sadagopan,Rajender
, p. 1572 - 1573 (2002)
The utility of glycine as a safety catch linker for the immobilization of alcohols and phenols to the solid-support is demonstrated by performing a variety of synthetic transformations.
Heterobimetallic Carbene Complexes Bearing Cyclometalated IrIII/RhIII and Mixed NHC∧ Py/PPh3 Coordinated PdII Centers: Structures and Tandem Catalysis
Majumder, Adhir,Nath Saha, Tarak,Majumder, Niladri,Naskar, Rajat,Pal, Kuntal,Maity, Ramananda
, p. 1104 - 1110 (2021)
Heterobimetallic complexes bearing NHC donor ligands are gaining immense popularity in organometallic chemistry and tandem catalysis. It is known that the NHC reacts with PdII in the presence of pyridine to yield PEPPSI type complexes and the NHC ligands having ortho-C?H proton easily orthometalate to IrIII or RhIII centers. Combining these two methodologies in a stepwise fashion, we present here a series of heterobimetallic IrIII?PdII and RhIII?PdII complexes from a dicarbene donor ligand featuring cyclometalated IrIII or RhIII and mixed (Formula presented.) /PPh3 coordinated PdII centers. All the heterobimetallic complexes have been structurally characterized by X-ray crystallographic analysis. The heterobimetallic complexes featuring mixed (Formula presented.) coordinated PdII centers show better activity in tandem Suzuki-Miyaura/transfer hydrogenation reactions compared to both, the heterobimetallic complexes possessing PEPPSI type PdIIcenters, and the equimolar mixture of their mononuclear PdII and RhIII or IrIII counterparts. The heterobimetallic complex featuring cyclometalated IrIII and mixed (Formula presented.) coordinated PdII center shows excellent selectivity for 4-biphenylmethanol (isolated yield: 92 %) in tandem catalysis.
Assessment of the reusability of Pd complexes supported on fluorous silica gel as catalysts for Suzuki couplings
Tzschucke, Carl Christoph,Andrushko, Vasyl,Bannwarth, Willi
, p. 5248 - 5261 (2005)
A thorough investigation of different perfluoro-tagged Pd complexes supported on fluorous silica gel (FSG) as catalysts for Suzuki reactions is presented. The rates of reaction upon recycling of the supported complexes were measured in order to determine the reusability of the catalysts. Perfluoro-tagged and untagged complexes adsorbed on FSG and unmodified silica gel were also compared. While with dimethoxyethane (DME) as a solvent the catalytic activity decreased upon reuse, significant activity was retained with recycled catalysts for reactions in water. With catalyst loadings of 0.001 mol-%, TONs as high as 526000 were obtained. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
Isolation of a metastable geometrical isomer of a hexacoordinated dihydrophosphate: Elucidation of its enhanced reactivity in umpolung of a hydrogen atom of water
Miyake, Hideaki,Kano, Naokazu,Kawashima, Takayuki
, p. 9083 - 9089 (2011)
Two of five conceivable geometrical isomers of a hexacoordinated dihydrophosphate bearing two sets of a bidentate ligand were investigated. X-ray crystallographic analysis of both of isomers, 1a-TPP and 1b-TEA, revealed their octahedral geometries of C2 and C1 symmetry, respectively, which were consistent with the NMR spectra. The isomer 1b-TEA underwent both hydride reduction of an aldehyde and proton exchange with water at room temperature in DMSO without any additive. A one-pot reaction of both of the reactions of 1b-TEA with D2O and an aldehyde or a ketone under the above conditions proceeded successfully to give the deuterated alcohol. Thus, umpolung of a hydrogen atom of water with 1b-TEA was achieved under much milder conditions than those used in the reaction with another isomer, 1a-TEA. Quantitative isomerization of 1b-TEA to 1a-TEA occurred in methanol at room temperature. Calculations on the five conceivable geometrical isomers of the anionic part of the dihydrophosphate revealed their relative stability, which reasonably explained the isomerization, and the larger negative charge at the atoms located at the trans positions of the oxygen atoms. The smaller coupling constants of the P-H and P-C bonds located at the rear of an oxygen atom in the NMR spectra resulted in the smaller s character of these bonds. The differences in both hydride-donation and proton-exchange reactivities between 1a-TEA and 1b-TEA could be explained by the differences in the atomic charge of the hydrogen atom and the stability difference of the initially formed phosphorane intermediates, respectively.
Novel Transformations of Zaragozic Acid A Derivatives with Cesium Fluoride
Girotra, Narindar N.,Ponpipom, Mitree M.
, p. 2485 - 2488 (1999)
C4-Hydroxy protected zaragozic acid A derivatives, upon treatment with CsF in DMF, underwent novel transformations to give tricyclic compounds. The process was initiated by intramolecular C3 proton abstraction by the C7 alkoxide anion to form the enolate ion, which can cyclie by two different pathways.
A Bifunctional Copper Catalyst Enables Ester Reduction with H2: Expanding the Reactivity Space of Nucleophilic Copper Hydrides
Kaicharla, Trinadh,Ngoc, Trung Tran,Teichert, Johannes F.,Tzaras, Dimitrios-Ioannis,Zimmermann, Birte M.
supporting information, p. 16865 - 16873 (2021/10/20)
Employing a bifunctional catalyst based on a copper(I)/NHC complex and a guanidine organocatalyst, catalytic ester reductions to alcohols with H2 as terminal reducing agent are facilitated. The approach taken here enables the simultaneous activation of esters through hydrogen bonding and formation of nucleophilic copper(I) hydrides from H2, resulting in a catalytic hydride transfer to esters. The reduction step is further facilitated by a proton shuttle mediated by the guanidinium subunit. This bifunctional approach to ester reductions for the first time shifts the reactivity of generally considered "soft"copper(I) hydrides to previously unreactive "hard"ester electrophiles and paves the way for a replacement of stoichiometric reducing agents by a catalyst and H2.
