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.
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.
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.
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.
Pd(OAc)2-biuret: A highly efficient, low cost and phosphine-free catalyst system for biaryl synthesis under aerobic conditions at room temperature
Saikia, Bishwajit
, (2021/05/10)
A highly efficient, less expensive and phosphine-free protocol for the Suzuki-Miyaura cross-coupling reactions of aryl halides and aryl boronic acids in iPrOH-H2O solvent under aerobic conditions has been developed. The results demonstrate that the biuret played a crucial role and making this protocol highly efficient. The Pd(OAc)2-biuret system exhibited superb catalytic activity towards the Suzuki-Miyaura cross-coupling reaction of a wide range of aryl halides with aryl boronic acids at room temperature, giving high yields even under very low catalytic loading. This system offers an attractive alternative to the existing protocols since the reaction proceeds in green solvent at room temperature with working simplicity, shorter reaction time, cost-effectiveness and provides the desired products in high yields. The effect of solvent, base as well as catalyst loading on the cross-coupling reaction of aryl halide with arylboronic acid is also described.
Four-Coordinated Manganese(II) Disilyl Complexes for the Hydrosilylation of Aldehydes and Ketones with 1,1,3,3-Tetramethyldisiloxane
Saito, Kyoka,Ito, Tatsuyoshi,Arata, Shogo,Sunada, Yusuke
, p. 1152 - 1156 (2020/12/18)
The coordinatively unsaturated manganase(II) bis(supersilyl) complex Mn[Si(SiMe3)3]2(THF)2 (2) was synthesized in one step via the reaction of MnBr2 with two equivalents of KSi(SiMe3)3 in THF. Complex 2 acts as an effective precatalyst for the catalytic hydrosilylation of aldehydes and ketones with 1,1,3,3-tetramethyldisiloxane (TMDS). The catalytic efficiency can be improved by combining 2 and adamantyl isocyanide (CNAd). The stoichiometric reaction of 2 and two equivalents of CNAd led to the isolation of Mn[Si(SiMe3)3]2(CNAd)2 (3) in high yield. Complex 3 shows superior catalytic performance than 2 in the hydrosilylation of relatively unreactive ketones.
Base promotedgem-difluoroolefination of alkyl triflones
Yang, Ren-Yin,Wang, Hui,Xu, Bo
supporting information, p. 4831 - 4834 (2021/05/25)
A new synthesis ofgem-difluoroalkenes from readily available alkyl triflones and difluorocarbene precursors such as TMSCF2Br has been reported. The reaction, regardless of electronic effect, givesgem-difluoroalkenes in good to excellent yields. The mechanism may involve deprotonation of triflones, nucleophilic addition, and the elimination of SO2CF3
