Copper-Free Sonogashira coupling in water with an amphiphilic resin-supported palladium complex

The palladium-catalyzed coupling reaction of aryl halides with terminal alkynes, the Sonogashira coupling, took place in water under copper-free conditions by use of an amphiphilic polystyrene-poly(ethylene glycol) (PS-PEG) resin-supported palladium-phosphine complex to give the corresponding aryl-substituted alkynes in high yields. The PS-PEG resin-supported palladium catalyst was recovered by simple filtration and reused four times without any loss of catalytic activity.     

An amphiphilic resin-supported palladium catalyst for high-throughput cross-coupling in water

[reaction: see text] The Suzuki-Miyaura coupling of aryl halides (8 varieties) and aryl- or vinylboronic acids (12 varieties) took place in water in the presence of a palladium complex of an amphiphilic polystyrene-poly(ethylene glycol) copolymer resin-supported N-anchored 2-aza-1,3-bis(diphenylphosphino)propane ligand and potassium carbonate to give uniform and quantitative yields of the corresponding biaryls (96 varieties).     

Asymmetric allylic amination in water catalyzed by an amphiphilic resin-supported chiral palladium complex

[reaction: see text] Catalytic asymmetric allylic amination of cycloalkenyl carbonates (methyl cyclohexen-2-yl carbonate, methyl cyclohepten-2-yl carbonate, methyl 5-methoxycarbonylcyclohexen-2-yl carbonate, methyl cyclohexenyl carbonate, tert-butyl 5-methoxycarbonyloxy-1,2,5,6-tetrahydropyridinedicarboxylate) with dibenzylamines ((C6H5CH2)2NH, (C6H5CH2)(4-CH3OC6H4CH2)NH, (4-CH3OC6H4CH2)2NH) was achieved in water under heterogeneous conditions by use of a palladium complex of (3R,9aS)-3-[2-(diphenylphosphino)phenyl]-2-phenyltetrahydro-1H-imidazo[1,5-a]indole-1-one anchored on polystyrene-poly(ethylene glycol) copolymer resin to give the corresponding cycloalkenylamines with high enantiomeric selectivity (90-98% ee).     

Asymmetric π-allylic etherification of cycloalkenyl esters with phenols in water using a resin-supported chiral palladium complex

Catalytic asymmetric etherification of cycloalkenyl esters with phenolic nucleophiles was achieved in water as the sole reaction medium under heterogeneous conditions by using 2 mol % palladium of a PS-PEG resin-supported palladium–imidazoindolephosphine complex to give optically active aryl(cycloalkenyl) ethers with up to 94% ee.     

Asymmetric nitroaldol reaction using nitromethane labeled with C

Nitro[¹¹C]methane produced from [¹¹C]O₂ reacted with several aldehydes in the presence of chiral metal catalyst prepared from LaLi₃{tris(binaphtoxide)}, n-BuLi, H₂O, and (R)-binaphtol. The molar ratios of La, Li, and binaphtol for effective catalysis in the ¹¹C-labeling were 1/4/4.5 and 1/4/6, respectively. The ¹¹C-nitroaldol products were obtained in 3-25% radiochemical yields with 39-51% ee within 20 min starting from the preparation of nitro[¹¹C]methane.     

Telomerization of allene with water catalyzed by palladium complexes

Conclusions The telomerization of allene with water catalyzed by palladium complexes leads to the preparation of 3-methyl-2-methylene-3-buten-1-ol and 2,3,6,7-tetramethylene-1-octanol in high yields.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2624–2626, November, 1985.     

Dimerization of isoprene in methanol using palladium complexes

Conclusions The systems Pd(acac)₂-Ph₃P and Pd(OAc)₂-Ph₃P cause the dimerization and telomerization of isoprene in methanol to give linear isoprene dimers and methoxydimethyloctadienes. In isopropanol these systems dimerize isoprene to 2,7-dimethyl-1,3,7-octatriene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2099–2100, September, 1976.     

Preparation of an amphiphilic resin-supported BINAP ligand and its use for rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid in water

[reaction: see text] The axially chiral bisphosphine ligand, 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (binap), was supported on a polystyrene-poly(ethylene glycol) copolymer (PS-PEG) resin and was used successfully for the rhodium-catalyzed asymmetric 1,4-addition of phenylboronic acid to alpha,beta-unsaturated ketones in water.     

PS-PEG resin-supported palladium-MOP complexes. Application in asymmetric π-allylic reduction

Homochiral palladium complexes of polymeric 2′-, 6-, and 6′-anchored 2-diphenylphosphino-1,1′-binaphthyl (MOP) ligands were prepared on polystyrene-poly(ethylene glycol) (PS-PEG) resin. The PS-PEG resin-supported palladium-MOP complexes exhibited high catalytic activity, stereoselectivity (up to 80% ee), and recyclability (six times) in the asymmetric allylic reduction of 1-vinyl-1,2,3,4-tetrahydronaphth-1-yl benzoate to give 1-vinyl-1,2,3,4-tetrahydronaphthalene.     

Chiral palladium complexes with monoterpenoids oximes

Oximes of cis-caran-4-one, 3α- and 3β-hydroxycaran-4-ones, cis-verbanone, menthone, and 2β-hydroxybornan-3-one have been synthesized. The obtained oximes react with lithium tetrachloropalladate to give new chiral palladium complexes containing mono-or bidentate oxime ligands.     

Improved Sonogashira CC coupling through clay supported palladium complexes with tridentate pincer bis-carbene ligands

Highly active recyclable Pd catalysts modified with a rigid C,N,C-tridentate pincer carbene ligand were successfully applied to the coupling of aryl halides with terminal acetylenes. The immobilization of Pd(II) complexes onto clays has beneficial effects on the recyclability of the catalytic activity over consecutive runs and also on the catalyst's stability, preventing it from Pd(0) formation.     

Forming biocompatible and nonaggregated nanocrystals in water using amphiphilic polymers

High-quality nanocrystals formed in organic solvents can be completely solubilized in water using amphiphilic copolymers containing poly(ethylene glycol) or PEG. These copolymers are generated using a maleic anhydride coupling scheme that permits the coupling of a wide variety of PEG polymers, both unfunctionalized and functionalized, to hydrophobic tails. Thermogravimetric analysis, size exclusion chromatography, cryogenic transmission electron microscopy, and infrared spectroscopy all indicate that the copolymers effectively coat the nanocrystals surfaces. The composite nanocrystal-polymer assemblies can be targeted to recognize cancer cells with Her2 receptor and are biocompatible if their surface coatings contain PEG. In the particular case of semiconductor nanocrystals (e.g., quantum dots), the materials in water have the same optical spectra as well as quantum yield as those formed initially in organic solutions.     

The Nitration of Pentamethylbenzene with Nitronium Hexafluorophosphate and water in nitromethane

The nitration of pentamethylbenzene in nitromethane has been studied under conditions that allow two mechanisms of nitration to be distinguished. One has been identified as nitration via the nitronium ion; the other nitration involves an oxidation of the molecular complex ArH-NO^⊕PF₆^? by nitrogen dioxide followed by reaction of the aromatic substrate with the incipient nitronium ion and loss of nitric oxide. Either reaction can be made predominant by an appropriate change in the proportions of the reactants in the system. A consideration of the σ-complexes formed by attack of the electrophile at aromatic carbon bearing a methyl substituent can provide a satisfactory explanation for the features observed in this and in other nitrations of pentamethylbenzene.     

Albumin-mediated asymmetric nitroaldol reaction of aromatic aldehydes with nitromethane in water

We succeeded in the asymmetric nitroaldol (Henry) reaction of aromatic aldehydes with nitromethane using human serum albumin (HSA) in water at neutral pH. The reaction of 4-nitrobenzaldehyde smoothly proceeded for 24 h at 30 °C to afford the corresponding (R)-2-nitro-1-(4-nitrophenyl)ethanol (27% ee). Lowering the reaction temperature to 0 °C improved the enantioselectivity (53% ee). Although the denatured HSA also catalyzed the coupling reaction, no enantioselectivity was observed. The reaction was also applicable to other substrates bearing various substitutions on the benzene ring, and the ee of (R)-1-(biphenyl-4-yl)-2-nitroethanol was up to 79% ee.     

The role of water molecules in formation of heterometallic palladium acetate complexes with cerium and neodymium

The reactions of palladium(II) acetate with neodymium(III) and cerium(III) acetates in acetic acid containing a specified amount of water have been studied. The following homo- and heterometallic complexes have been synthesized and characterized by X-ray diffraction: Nd₂(μ-OOCMe)₂(μ,η²-OOCMe)₂(η²-OOCMe)₂(HOOCMe)₂(OH₂)₂ · 4HOOCMe, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 2HOOCMe · 6H₂O, [Pd(μ-OOCMe)₄Ce(OH₂)₂(μ,η²-OOCMe)]₂ · 14H₂O, [Pd(μ-OOCMe)₄M(HOOCMe)₂(OH₂)₂]⁺ [Pd(μ-OOCMe)₄M(μ-OOCMe)₄Pd]⁻ · 2MeCOOH · 1.5H₂O (M = Nd, Ce), and {[Pd(μ-OOCMe)₄Ce(OOCMe)₄]₂ [Pd₄(μ-OOCMe)₄]₂(μ₄-O)₈CePd₄}(OH)₃ · 27H₂O. From kinetic and structural data and optical spectra of reaction solutions, the conclusion was drawn that hydrolytic processes play a decisive role in complexation reactions.