Oxazoline Complexes Research Articles

Half-Sandwich Ruthenium Phenolate–Oxazoline Complexes: Experimental and Theoretical Studies in Catalytic Transfer Hydrogenation of Nitroarene

In this work, five ruthenium complexes [Ru(p-cymene)LCl] containing phenolate-oxazoline ligands [L = 2-(4,5-dihydrooxazol-2-yl)phenol (1); L = 2-(4-methyl-4,5-dihydrooxazol-2-yl)phenol (2); L = 2-(4-ethyl-4,5-dihydrooxazol-2-yl)phenol (3); L = 2-(4-phenyl-4,5-dihydrooxazol-2-yl)phenol (4); and 2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)phenol (5)] were synthesized and characterized. The solid-state structures of all ruthenium complexes were determined by single-crystal X-ray diffraction. The catalytic activities of these complexes in the transfer hydrogenation reaction of nitroarene to aniline were investigated. Aniline and their derivatives were obtained in good to excellent yields with isopropanol as the hydride source. The present protocol provides an environmentally benign synthetic method for the reduction of nitroarenes to anilines without employing harsh reaction conditions. Theoretical studies employing density functional theory were carried with the aim to propose a feasible reaction mechanism and to...

A silica-supported palladium-bis(oxazoline) complex efficiently catalyzes the synthesis of cinnamic acid derivatives via Mizoroki–Heck coupling reactions

A palladium(II)-bis(oxazoline) complex supported on silica (Pd-BOX-Si) was prepared, characterized and applied as a catalyst in Mizoroki–Heck cross-coupling reactions. The bis(oxazoline) (BOX) ligand has a hydroxyl group that can be anchored to 4-benzyl chloride-functionalized silica gel, followed by the coordination of palladium(II) chloride. The catalytic activity and the recyclability of Pd-BOX-Si have been investigated in the production of cinnamic acid derivatives via Mizoroki–Heck coupling reactions of acrylates with aryl halides; The Pd-BOX-Si catalyst demonstrated excellent catalytic activity. Characterization of the recycled Pd-BOX-Si catalyst revealed its good stability under the reaction conditions employed.

New palladium-oxazoline complexes: Synthesis and evaluation of the optical properties and the catalytic power during the oxidation of textile dyes.

The present paper describes the synthesis of new palladium–oxazoline complexes in one step with good to high yields (68–95%). The oxazolines were prepared from enantiomerically pure α-aminoalcohols. The structures of the synthesized palladium complexes were confirmed by NMR, FTIR, TOFMS, UV–visible spectroscopic analysis and X–ray diffraction. The optical properties of the complexes were evaluated by the determination of the gap energy values (Eg) ranging between 2.34 and 3.21 eV. Their catalytic activities were tested for the degradation of Eriochrome Blue Black B (a model of azo dyes) in the presence of an ecological oxidant (H2O2). The efficiency of the decolorization has been confirmed via UV–visible spectroscopic analysis and the factors affecting the degradation phenomenon have been studied. The removal of the Eriochrome reached high yields. We have found that the complex 9 promoted 84% of color elimination within 5 min (C0 = 30 mg/L, T = 22 °C, pH 7, H2O2 = 0.5 mL) and the energetic parameters have been also determined.

Asymmetric Diels-Alder Reaction of 2-Arylidene-1,3-indanediones with 2-Vinylindoles Catalyzed by a Sc(OTf)3/Bis(oxazoline) Complex：Enantioselective Synthesis of Tetrahydrocarbazole Spiro Indanedione Derivatives

报道了Sc(OTf)3/Bis(oxazoline)复合物催化的2-芳基-1,3-茚二酮与2-乙烯基吲哚的不对称Diels-Alder反应,简便、高效的构建了一系列手性四氢咔唑螺茚酮衍生物.通过考察不同的金属盐和手性配体、溶剂、温度等因素对反应的影响,获得了优良的收率(up to 92%yield)和优异的对映选择性(up to 94%ee).该反应条件温和,具有宽广的底物适用范围和较好的官能团兼容性.

Diastereoselective Synthesis of Chiral Octahedral Iridium(III) Phosphano–Oxazoline Complexes

Reaction of the dimer [Ir(μ-Cl)(η2-coe)2]2 (coe = cyclooctene) with chiral phosphano–oxazoline ligands (PN*) renders neutral mononuclear iridium(I) complexes of the formula [IrCl(η2-coe)(PN*)] (1, 2), which in turn are oxidized to the corresponding iridium(III) hydride species [IrCl2H(η2-coe)(PN*)] (3, 4) by treatment with aqueous HCl. The latter react with diphosphanes (PP) in the presence of NaSbF6 to afford cationic complexes of stoichiometry [IrClH(PN*)(PP)][SbF6] (5–16). The fluorophenyldiphosphane-containing compounds [IrClH(PN*)(dfppe)][SbF6] (15, 16) evolve to the corresponding Ir(I) species [Ir(PN*)(dfppe)][SbF6] (17, 18) by HCl loss. The new compounds have been fully characterized by analytical and spectroscopic means, including the molecular structure determination of [IrCl2H(η2-coe)(PNInd)] (3), [IrClH(PNInd)(dppen)][SbF6] (6a,b), [IrClH(PNInd)(dppp)][SbF6] (7a), [IrClH(PNiPr)(dppp)][SbF6] (13a), [IrClH(PNInd)(dfppe)][SbF6] (15), [Ir(PNInd)(dfppe)][SbF6] (17), and [Ir(PNiPr)(dfppe)][SbF6] (18)...

ChemInform Abstract: Iridium Catalyzed Enantioselective Hydrogenation of α‐Alkoxy and β‐Alkoxy Vinyl Ethers.

AbstractA variety of functionalized acid‐sensitive vinyl ethers is successfully hydrogenated in the presence of a chiral Ir—N‐carbene—oxazoline complex (ICOC).

Iridium catalyzed enantioselective hydrogenation of α-alkoxy and β-alkoxy vinyl ethers

Iridium catalyzed, enantioselective hydrogenations of functionalized, acid-sensitive vinyl ethers are reported. These reactions are mediated by the chiral N-carbene–oxazoline complex 1 that, unlike similar N,P-ligated catalysts (6 and 7), gives hydrogenation products (with enantioselectivities up to 96%) without significant acid-mediated degradation. In general, higher enantioselectivities were observed for the allylic alcohol derivatives (2) than the α-methoxycinnamate-based compounds (4).

Recycling Chiral Copper Bis(oxazoline) Complexes in an Original Multireaction Procedure

Recycling Chiral Copper Bis(oxazoline) Complexes in an Original Multireaction Procedure

Platinum-oxazoline complexes as anti-cancer agents: syntheses, characterisation and initial biological studies

The syntheses, characterisation and biological activities (IC50; DNA binding) of four mononuclear Pt oxazoline complexes are reported. These materials are the compounds cis-[PtCl2(NH3)(Etox-κ1N)] (1: Etox = 2-ethyl-2-oxazoline), [PtCl2(anilox-κ2N,N′)] (2: anilox = 4,4-dimethyl-2-[o-anilinyl]-2-oxazoline), cis-[PtCl2(Etox-κ1N)2] (3) and [PtCl(pyox-κ3N,N′,N′)] (4: pyoxH = pyridine-2-carboxyanil-[o-{4,4-dimethyl-2-oxazolinyl}-ide]) and all four are shown to have slightly lower cytotoxicities in vitro when compared to cisplatin against the A2780 ovarian cancer cell line. These new materials all appear to be bio-active via the formation of DNA adducts. Complexes 1 and 2 have been further characterised in the solid-state by X-ray diffraction methods.

ChemInform Abstract: Enantioselective Hydrogenation of α‐Aryloxy and α‐Alkoxy α,β‐Unsaturated Carboxylic Acids Catalyzed by Chiral Spiro Iridium/Phosphino‐Oxazoline Complexes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Solvent-Free Method for Making Dioxolane and Dioxane from the Biorenewables Glycerol and Furfural Catalyzed by Oxorhenium(V) Oxazoline

Low catalyst loading of a cationic oxorhenium(V) oxazoline complex, [2-(2'-hydroxyphenyl)-2-oxazolinato(-2)]oxorhenium(v), condenses diols and aldehydes to give 1,3-dioxolanes in excellent yields under neat conditions and reasonably mild temperatures. The reaction is applicable to biomass-derived furfural and glycerol. The resulting cyclic acetals may find use as value-added chemicals and/or oxygenate fuel additives. Differences in the stereoselectivity of the reaction for epoxides versus diols provide insight into the reaction mechanism.

Catalytic oxidation of sulfides to sulfoxide using manganese(III) complexes with bidentate O,N-donor oxazoline ligand and UHP oxidizing agent

Abstract The efficient catalytic systems were investigated for the oxidation of various sulfide by manganese(III)–oxazoline complexes, [Mn(phox)2(MeOH)2]ClO4 and Mn(phox)3 (Hphox = 2-(2′-hydroxyphenyl)oxazoline). These complexes were found efficient catalysts for the oxidation of sulfides with urea hydrogen peroxide (UHP) in short reaction times (5 min) and under mild condition. Sulfoxides were obtained as the main products together with variable amounts of sulfones. The efficiency of the catalytic system was strongly influenced by the nature of solvents and axial ligands so the best yields were achieved in a mixture of methanol: dichloromethane and in the presence of imidazole as co-catalyst.

Asymmetric Hydrogenation Approaches to Valuable, Acyclic 1,3-Hydroxymethyl Chirons

An iridium carbene oxazoline complex was used to catalyze hydrogenations of trisubstituted alkenes to give terminal and internal 1,3-hydroxymethyl chirons. The products are accessible in all possible stereoisomeric forms. These hydrogenations do not require strongly coordinating functionalities on the substrate, and in some key cases, catalyst- rather than substrate-controlled stereoselectivities are observed. It is hypothesized that these reactions would not be feasible using iridium or rhodium diphosphine complexes.

Synthesis and characterization of novel tantalum(V) complexes containing oxazoline and DMA ligation

Two six coordinate tantalum(V) oxazoline complexes, [Ta(OX)(NMe 2) 4] ( 1) and [Ta(OX) 2(NMe 2) 3] ( 2), formed by the reaction of [Ta(NMe 2) 5] with the chelating di-nitrogen ligand 4,4-dimethyl-2-pyrrole-2-oxazoline in 1:1, 1:2 and/or 1:3 molar ratios have been investigated. The structural study of 1 and 2 by X-ray crystallography shows that they both adopt geometries best described as distorted octahedral with N–Ta–N angles of 172.6(3)° and 169.4(2)°, respectively. The nitrogen atoms of the oxazoline are bound directly to the tantalum, leading to a five-membered metallacycle in the basal plane. The N–Ta–N and Ta–N–C angles of the basal five-membered oxazoline ring are 71° and 113–117°, respectively.

Synthesis, crystal structure and catalytic activity of a novel Mo(VI)–oxazoline complex in highly efficient oxidation of sulfides to sulfoxides by urea hydrogen peroxide

Novel molybdenum complex, cis-[MoO 2(phox) 2] has been synthesized and characterized by IR, 1H NMR, elemental analyses (CHN), and X-ray molecular structure determination methods. This complex was found to be an efficient, selective catalyst for the oxidation of various sulfides to sulfoxides with urea hydrogen peroxide (UHP) in excellent yields (100% for diallylsulfide) and short reaction times (20 min) at room temperature. The catalytic system oxidizes diallylsulfide chemoselectively to its corresponding sulfoxide without any over oxidation in double bond.

Enantioselective Ketone Hydrogenation: From R&D to Pilot Scale with Industrially Viable Ru/Phosphine−Oxazoline Complexes

The development of a pilot process for the enantioselective hydrogenation of 3,5-bistrifluoromethyl acetophenone (BTMA) using a Ru/phosphine−oxazoline complex in toluene in the presence of aqueous NaOH is described. Various reaction parameters and quality risk factors such as ligand structure, substrate quality, reaction conditions, thermal safety, etc. were investigated. The reaction was carried out twice on a 140-kg scale at 20 bar and 25 °C with substrate-to-catalyst ratios of 20,000 with an enantiomeric excess of >95%. After crystallization, (R)-3,5-bistrifluoromethyl phenyl ethanol (BTMP) was obtained with an ee between 97.7 and 98.6% in 70% chemical yield.

Catalytic activity of manganese(III)-oxazoline complexes in urea hydrogen peroxide epoxidation of olefins: The effect of axial ligands

The catalytic activity of two manganese(III)-oxazoline complexes [Mn(phox) 2(CH 3OH) 2]ClO 4 and Mn(phox) 3 (Hphox = 2-(2′-hydroxylphenyl)oxazoline), was studied in the epoxidation of various olefins. All of epoxidation reactions were carried out in (1:1) mixture of methanol:dichloromethane at room temperature using urea hydrogen peroxide (UHP) as oxidant and imidazole as co-catalyst. The epoxide yields clearly demonstrate the influence of steric and electronic properties of olefins, the catalysts and nitrogenous bases as axial ligand. [Mn(phox) 2(CH 3OH) 2]ClO 4 catalyst with low steric properties has higher catalytic activity than Mn(phox) 3. The highest epoxide yield (95%) was achieved for indene at the presence of [Mn(phox) 2(CH 3OH) 2]ClO 4 within 5 min. The proximal and distal interactions of strong π-donor axial ligands such as imidazole with the active intermediate are efficiently increased activity of the catalytic system.

Oxazoline Chemistry. Part 11. Syntheses of Natural and Synthetic Isoflavones, Stilbenes and Related Species via C—C Bond Formation Promoted by a Pd—Oxazoline Complex.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Oxazoline Chemistry. Part 11: Syntheses of natural and synthetic isoflavones, stilbenes and related species via C–C bond formation promoted by a Pd–oxazoline complex

The complex trans-[PdCl 2(2-ethyl-2-oxazoline-κ 1 N) 2] ( 1 ) is shown to be an active and oxidatively robust catalyst for C–C bond forming reactions (Heck, Sonogashira, Ullmann, Miyaura–Suzuki, etc.). These reactions can be carried out in air without rigorous solvent/substrate purification and in the absence of additional free ligand. The general methodology described above has been applied to the high yield and regio-selective formation, via Miyaura–Suzuki coupling, of natural and synthetic isoflavones (i.e., isoflavone, 2′-methylisoflavone [ 7b ], 3′-methylisoflavone [ 7c ] and 3′,4′-benzoisoflavone: [ 7d ]). Compounds 7c and 7d are previously unknown. In addition, the synthesis of ( E)-tris- O-methylresveratrol and ( E)-3,5-dimethoxystilbene is also described; the former is a recognized anti-cancer agent while the latter is a biologically active extract from the bark of the conifer species Pinus armandii. Both of these latter products are produced as a result of a Heck coupling reaction promoted by 1 .

Development of a Novel Chiral Spiro Ligand Bearing Oxazoline.

Abstract The synthesis of bis(oxazoline) ligand 1 bearing a spiro skeleton is achieved via double ring-closing metathesis (RCM) of tetraene 2 and subsequent oxazoline ring formation using N-bromosuccinimide (NBS). The Cu-spiro bis(oxazoline) complexes prepared from 1 and Cu(OTf)2 or Cu(OAc)2 act efficiently as chiral catalysts for promoting carbonyl-ene reactions or Henry reactions with good enantiocontrol.