Complexes of palladium,platinum and rhodium with 2,2′-biquinoline and 2-(2′-pyridyl)quinoline

Summary The reactions of 2,2-biquinoline(biq) with M(PhCN)₂X₂ (M=Pd; X=Cl or Br; M=Pt, X=Cl, Br or I), K₂PtCl₄ and RhCl₃·3H₂O and of 2-(2-pyridyl)quinoline (pq) with K₂PtCl₄ and RhCl₃·3H₂O have been investigated. The isolated complexescis-[Pd(biq)X₂] (X=Cl or Br),cis-[Pt(biq)Cl₂],cis-[Pt(biq)Cl₂]·H₂O,trans-[Pt(biq)₂Br₂]·5H₂O, [Pt₃(biq)₂I₆],mer-[Rh(biq)Cl₃-(H₂O)] andmer-[Rh(pq)Cl₃(H₂O)] have been characterized by elemental analyses, conductivity measurements, i.r., electronic, and¹H n.m.r. spectra. The reaction of pq with K₂PtCl₄ in 1M H₂SO₄ gave the salt 2-(2-pyridyl) quinolinium tetrachloroplatinate(II) pentahydrate, (pqH)₂[PtCl₄]·5H₂O; when the reaction was carried out in aqueous acetone,cis-[Pt(pq)Cl₂] was obtained. A new method for the synthesis ofcis-[Rh(biq)₂X₂]X (X=Cl or Br) is described; both compounds have been further characterized by¹H n.m.r.     

Is rhodium tetroxide in the formal oxidation state VIII stable? a quantum chemical and matrix isolation investigation of rhodium oxides

The structures and reactions of different rhodium oxides and dioxygen complexes with RhO₄ stoichiometry were investigated by matrix isolation infrared spectroscopy and quantum chemical calculations. The inserted RhO₂ molecule reacted with dioxygen upon sample annealing to form the [(??¹-O₂)RhO₂] complex, which can further isomerize to the known [(??²-O₂)RhO₂] complex via infrared irradiation. Both experimental and theoretical studies suggest that the [(??¹-O₂)RhO₂] complex has a doublet ground state with non-planar C _s symmetry in which the O₂ ligand is end-on bonded to the rhodium centre. Although rhodium tetroxide is predicted to be a stable molecule with D _2d symmetry at different level of theory, no evidence is found for the formation of this Rh(VIII) species in noble gas matrices. Our experiments also suggest the formation of a new peroxo [Rh(??²-O₂)₂] complex, which is calculated to have a doublet ground state with D _2d symmetry. This peroxo complex undergoes isomerization to the known superoxo [Rh(??²-O₂)₂] complex via the rotation of the dioxygen ligand under infrared irradiation.     

The rate of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid as a function of the electronic properties of substituents

The kinetic regularities of cyclization of 2′- and 4′-substituted diphenylamine-2-carboxylic acids in sulfuric acid were determined. The rate of cyclization of diphenylamine-2-carboxylic acids is linearly dependent on the nature of substituents in the meta-position relative to the reaction site in accordance with the two-parameter Hammett equation.     

Synthetic strategies to 2′-hydroxy-4′-methylsulfonylacetophenone,a key compound for the preparation of flavonoid derivatives

Different strategies for the synthesis of 2′-hydroxy-4′-methylsulfonylacetophenone are reported in the present paper. This compound is considered as a key synthon for the synthesis of new flavonoid derivatives designed as potential cyclooxygenase-2 inhibitors. The retrosynthetic approach via 3′-methylsulfonylacetophenone, which included three synthetic pathways, did not allow us to obtain the expected compound. However, a synthesis from 3-mercaptophenol led to the desired acetophenone in three steps: thiophenol methylation, Friedel–Crafts acetylation and oxidation of the sulphide to the corresponding sulfone. The desired compound, 2′-hydroxy-4′-methylsulfonylacetophenone, will be used as a synthon for the preparation of novel flavonoid derivatives, such as 2′-hydroxychalcones, flavanones, flavones, and flavonols.     

Expression and Purification of Biologically Active Human FGF2 Containing the b′a′ Domains of Human PDI in Escherichia coli

Among the members of the fibroblast growth factor (FGF) family that affect the growth, differentiation, migration, and survival of many cell types, FGF2 is the most abundant in the central nervous system. Because of its wound healing effects, FGF2 has potential as a therapeutic agent. The protein is also added to the culture media to maintain stem cells. Expression and purification procedures for FGF2 that are highly efficient and low cost have been intensively investigated for the past two decades. Our current study focuses on the purification of FGF2 fused with b′a′ domains of human protein disulfide isomerase to elevate overexpression, solubility, and stability with a simplified experimental procedure using only ion exchange chromatography, as well as on the confirmation of the biological activity of FGF2 on fibroblast Balb/c 3T3 cells and hippocampal neural cells.     

New semiquinone-catecholate rhodium complex with 2,2′-dipyridyl

A new semiquinone rhodium complex,viz., (2,2′-dipyridyl)(3,6-di-tert-butyl-o-benzosemiquinone)(3,6-di-tert-butylcatecholate)rhodium(III) (1), which is a structural analog of the known redox-isomeric cobalt complex, was prepared, isolated in the individual state, and characterized by X-ray analysis, magnetochemistry, and IR and ESR spectroscopy. At room temperature, compound1, unlike the cobalt analog, is a complex of trivalent low-spin rhodium with one catecholate and one semiquinone ligand. However, broadening of the lines in the ESR spectra both of a solution and a powder of complex1 with increasing temperature indicates that the redox-isomeric transformation occurs in this case as well. The equilibrium of this transformation is virtually completely shifted toward the low-spin semiquinone-, catecholate isomer. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1784–1788, September, 1999.     

Resolution and determination of the absolute configuration of 3,3′4,4′-tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid

(±)-3,3′4,4′-Tetramethyl-1,1′-diphosphaferrocene-2-carboxylic acid 1 was resolved via diastereomeric salts with brucine. The (R)-absolute configuration of (+)-1 was determined by X-ray crystallography.     

New route for the synthesis of 2-thiouracil analogues of 3′-azido-2′,3′-dideoxy nucleosides

Summary Reaction of 3-azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranoside (5) with silylated 2-thiouracil and 5-alkoxy-2-thiouracils in the presence of trimethylsilyl trifluoromethanesulfonate afforded an anomeric mixture of the corresponding 3-azido-2,3-dideoxy-2-thiouridine derivatives with the -anomer as the main product. Deprotected nucleosides were obtained by treatment with tetrabutylammonium fluoride.

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Ein neuer Weg zur Synthese von 2-Thiouracil-Analogen von 3-Azido-2,3-dideoxy-Nucleosiden

Zusammenfassung Die Reaktion von 3-Azido-5-O-tert-butyldiphenylsilyl-2,3-dideoxy-D-erythro-pentofuranosid (5) mit silyliertem 2-Thiouracil und 5-Alkoxy-2-thiouracil in Gegenwart von Trimethylsilyltrifluormethansulfonat ergab eine anomere Mischung der entsprechenden 3-Azido-2,3-dideoxy-2-thiouridin-Derivate, wobei das -Anomer das Hauptprodukt darstellte. Die ungeschützten Nucleoside wurden mittels Behandlung mit Tetrabutylammoniumfluorid erhalten.

     

Carbonyl ylide formation from the rhodium (II) acetate catalyzed reaction of a α-diazoketone

Reaction of the α-diazoketone derived from 7-carboxyphthalide with rhodium acetate results in an internal cyclization to give a six-ring carbonyl ylide which is subsequently converted to 7-carbomethoxyphthalide.     

O-Heterocycles by the cyclization of side-chain bromomethoxylated 2′-acetoxychalcones

Summary The title chalcone derivatives react with aqueous sodium hydroxide of various concentrations to form aurones as the major product, together with small amounts of flavones. However, the introduction of 4-nitro or 4-chloro substituents resulted in the formation of flavones as the major product.

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O-Heterocyclen mittels Cyclisierung von an der Seitenkette brommethoxylierten 2-Acetoxychalconen

Zusammenfassung Die im Titel genannten Chalconderivate reagieren mit Natronlauge in verschiedenen Konzentrationen, wobei Aurone zusammen mit geringen Mengen an Flavonen entstehen. Die Einführung von 4-Nitro- oder 4-Chlor-Substituenten führte jedoch zur bevorzugten Bildung von Flavonen.

     

The synthesis of 2′-homouridine,its incorporation into a dinucleoside monophosphate and hydrolytic behaviour of the dimer

An efficient route to 2′-homouridine (1), a new nucleoside analogue, is reported that is based on an ene reaction. This nucleoside has been incorporated into a dinucleoside monophosphate and hydrolytic studies on the dimer show that it does not behave like a ribonucleotide.     

Isolation of a PBP-pincer rhodium complex stabilized by an intermolecular C-H σ coordination as the fourth ligand

A little help from my friends: a highly reactive, 16-electron square-planar rhodium complex was isolated. This species displays an intermolecular interaction between the rhodium and the C-H bond of another molecule as the fourth ligand to form an infinite network in the crystal lattice. The complex undergoes oxidative addition to the O-H bond of phenol or a primary alkyl alcohol to give the corresponding hydrido-phenoxido Rh(III) complex or carbonyl Rh(I) complex, respectively.     

Synthesis of a Diterpene 1,3,4-Oxadiazolin-2′-one from Dimethylcyclopentenonepimarate

A diterpene 1,3,4-oxadiazolin-2-one was synthesized by lead-tetraacetate oxidation of 16,17- epoxydimethylcyclpentenonepimarate. The structures of the synthesized compounds were confirmed by IR and NMR spectroscopies.     

The Synthesis of a New Dumbbell-shaped Compound of Bis-4, 4′-bipyridine Bridged by 2, 2′-Bipyridine

The title compound 5 was synthesized in 45% yield by the reaction of compound 3 with α,α′-bis (bromomethyl)-2, 2′-bipyridine in CH3CN at 70℃ for 24 h.     

Total synthesis of baiyunoside by a novel 2′ discriminated glycosidation

Total synthesis of a sweet taste glycoside with labdane diterpenoid, baiyunoside (1), has been accomplished from (±)-baiyunol (2) by a novel 2′ discriminated glucosidation using 3b followed by the introduction of xylosyl moiety using 3c according to Noyori's procedure.     

A silver(I)–rhodium(I) cooperative catalysis in the reaction of N′-(2-alkynylbenzylidene)hydrazide with 2-vinyloxirane

A novel and efficient route to H-pyrazolo[5,1-a]isoquinoline-1-carbaldehydes via a tandem reaction of N′-(2-alkynylbenzylidene)hydrazide with 2-vinyloxirane is described. The reaction proceeds through a silver(I)–rhodium(I) cooperative catalysis.     

Synthesis of 5,5′-Dialkyl-6,6′-dichloro-2, 2′-bipyridines

5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines.     

Structures of the crystalline supramolecular associates of imidazole with 1,1′-binaphthyl-8,8′-dicarboxylic acid and 2,2′-dihydroxy-1,1′-binaphthyl. Spatial similarity of the acid associate crystal packing to the active site of a serine protease

Abstract

Crystal structure analysis of the imidazole associates with 1,1′-binaphthyl-8,8′-dicarboxylic acid (1), [1a, triclinic, P1, a = 7.569(4), b = 8.393(2), c = 8.634(1) Å, α = 93.21(2), β = 106.88(3), γ = 105.17(3)°, D_c = 1.36 g/cm³, Z = 1, R = 0.045 for 1031 data] and with 2,2′-dihydroxy-1,1′-binaphthyl (2), [2a, tetragonal P4₁2₁2, a = 8.519(1), c = 29.821(2), D_c = 1.30 g/cm³, Z = 4, R = 0.051 for 1236 reflections] revealed 1:1 and 1:2 stoichiometry, respectively. Spontaneous resolution occur during crystallization in both compound crystals. 1a is a salt-like associate with hydrogen bonds between the carboxylate and imidazolium ion pairs while the neutral 2a has also well defined hydrogen bonds between host and guest molecules. In a modeling experiment corresponding Brookhaven Protein Data Bank atomic coordinates from the active site of the bacterial serine protease enzyme Subtilisin BPN were fitted to the crystal packing of the small molecule associate 1a crystal. The relative displacement of the ion pair components and a symmetry related carboxyl function in 1a has fair steric resemblance to similar moieties in the active site of Subtilisin (Δ_ave = 0.24 Å for 9 fitted atoms). The agreement in the results of two fully independent and totally different (i.e. a native protein active site and an artificial small molecule associate) crystal structure determinations underlines the assumed conceptual similarity of crystals (“giant supramolecules”) to protein sequences optimized through evolution.