Enantioselective Deprotonation/Electrophile Addition Reactions of Tricarbonyl(phenyl carbamate)chromium Complexes

Sequential reaction of the tricarbonyl[(η⁶-phenyl) carbamate]chromium complex 3 with chiral amide bases (see 4 and 5 ) and electrophiles yielded planar chiral ortho-substituted complexes 6 with up to 70% enantiomeric excess (ee) (Scheme 2, Table 1 and 2). The enantiomer purity could be increased to >90% ee by fractional crystallization. In all but one case the racemate crystallized selectively, leaving the enantiomerically enriched complex in solution. X-Ray crystal-structure analyses of rac- 6a and (1R)- 6a suggest that this can be ascribed to a more favorable packing of enantiomers of opposite configuration in the solid state than that of the enantiomerically pure solid. Increasing the temperature of the intermediate ortho-lithiated aryl carbamate complex induced an anionic ortho-Fries rearrangement: The 1,3-transposition of the carbamoyl group yielded the ortho-substituted (η⁶-benzamide)tricarbonylchromium complexes 10 in 65% yield, after exposure to the electrophile (Scheme 6), and the use of a chiral amide base 5 in the deprotonation step afforded the product with an ee of 54%.     

Prediction of ortho(β) 13C chemical shifts in conjugated systems

An equation has been developed which relates ortho or C-β ¹³C substituent chemical shifts (SCS) to the ortho proton–proton coupling constant in the unsubstituted member of a conjugated series. This method is an extension of previous equations which have been used to predict ortho ¹H SCS values, and has its origin in a relationship between bond order and SCS values. The equation was derived from ortho ¹³C data in 2-naphthalenes and monosubstituted benzenes and its application to other unsaturated series is discussed.     

Asymmetric Cyclizative Dimerization of (ortho-Alkynyl Phenyl) (Methoxymethyl) Sulfides with Palladium(II) Bisoxazoline Catalyst

The first example of an asymmetric cyclization–dimerization of (ortho-alkynyl phenyl) (methoxymethyl) sulfides with a palladium(II) bisoxazoline (box) catalyst has been developed. The box ligand enhances the alkynophilicity of benzothienyl palladium(II) intermediate A and thus promotes coordination of the second alkyne substrate, leading to the dimerization. The characteristic properties of the box ligand were supported by density functional theory (DFT) calculations of the intermediate. Axially chiral bibenzothiophenes were obtained in good yields with good enantioselectivities.     

Homogeneous Catalysis of C-H Bond Activation by a Novel Ruthenium(III)-Complex

A novel mixed-ligand [Ru^III(amp)(pic)(H₂O)] complex (1) (H₂amp = N-(hydroxyphenyl)salicyldimine; pic = picolinate) has been synthesized and characterized by physico-chemical methods. Complex 1has been found to be an effective catalyst in oxo-functionalization of C-H bond of organic substrates by using tert-butyl hydroperoxide (t-BuOOH) as a terminal oxidant. Formation of a high valent Ru(V)-oxo species as catalytic intermediate is proposed to be the source of oxygen atom in the oxidised product.     

Studies of the catalytic activity of Fe(III)(salen) complexes as epoxidation catalysts

Two new Fe(III)(salen) complexes, FeL¹ClO₄·2H₂O (1) and FeL²ClO₄ (2) [L¹ = N,N′-ethylenebis(3-formyl-5-methylsalicylaldimine) and L² = N,N′-cyclohexenebis(3-formyl-5-methylsalicylaldimine)], have been synthesized and characterized. The catalytic activity of the complexes for epoxidation of alkenes has been investigated in the presence of two terminal oxidants PhIO and NaOCl, with two solvents CH₃CN and CH₂Cl₂. As alkenes styrene and (E)-stilbene have been chosen for investigation; styrene is a better substrate than electron-rich (E)-stilbene. The study also suggests that unlike their Mn(III) counterparts, 1 and 2 are poor epoxidation catalysts; catalysis proceeds with formation of one intermediate, rather than forming more than one intermediate depending on the terminal oxidant used. Use of exogenous neutral donor ligands such as Py, PyNO and 1-MePy is effective to improve catalytic behavior.     

Metal cation-induced multifluorescence of azacrown-substituted (tetrafluorophenyl)imidazo[1,2-a]pyridine

ortho-Azacrown-substituted (tetrafluorophenyl)imidazo[1,2-a]pyridine (2) in an acetonitrile solution emits 380 nm light in the presence of Li⁺ cation and emits 460 nm light in the presence of Zn²⁺, Mg²⁺ or H⁺ cation. In contrast, para-azacrown-substituted analogue (1) emits three different fluorescent lights responding to Li⁺, Zn²⁺ or H⁺ cation, respectively; 388 nm light to Li⁺ cation, 433 nm light to Zn²⁺ cation or 469 nm light to H⁺ cation.     

Efficient Synthesis of (S)-3-(4-Fluorophenyl)morpholin-2-one,a Key Chiral Intermediate of Aprepitant

A facile, economical, and practical method for the preparation of (S)-3-(4-fluorophenyl)morpholin-2-one [(S)-9] has been developed from ethyl 2-(4-fluorophenyl)-2-oxoacetate (7) in three steps through cyclization, hydrogenation, and resolution, providing a new and convenient access to the key intermediate of antiemetic drug aprepitant.     

Synthesis and Application of Tetrahydro‐2H‐fluorenes by a Pd(0)‐Catalyzed Benzylic C(sp3)−H Functionalization

A new method has been developed for the synthesis of tetrahydro‐2H‐fluorenes based on a Pd(0)‐catalyzed benzylic C(sp³)?H functionalization. Importantly, the success of the cyclization step was dependent on there being substituents at the two positions ortho to the benzylic group to avoid an undesired C(sp²)?H functionalization. This method was subsequently used to prepare the right‐hand fragment of the hexacyclic triterpenoid benzohopanes, and therefore represents a powerful tool for the construction of the related compounds.     

L-鼠李糖基(氨基)硫脲类化合物的合成

以L-鼠李糖为起始原料, 制备1-溴-2,3,4-三-O-乙酰基-β-L-吡喃型鼠李糖, 然后在甲苯中与Pb(SCN)₂作用, 得到中间体2,3,4-三-O-乙酰基-α-L-吡喃型鼠李糖基异硫氰酸酯(1). 利用2,3,4-三-O-乙酰基-α-L-吡喃型鼠李糖基异硫氰酸酯易发生亲核加成的性质, 在不同溶剂中, 与取代的苯并噻唑胺(2a～2f)、取代的苯并噻唑肼(2g～2l)、氧化和非氧化的哒嗪酮甲酰肼(2m, 2n)以及取代的嘧啶胺(2o, 2p)反应, 合成了16种新的(氨基)硫脲类化合物3a～3p. 所有化合物的结构均经IR, ¹H NMR, LC-MS和元素分析确证, 并对它们的生物活性做了初步测试.     

Poly(ortho‐toluidine) Modified Carbon Paste Electrode: A Sensor for Electrocatalytic Reduction of Nitrite

The electrocatalytic reduction of nitrite has been studied by poly(ortho‐toluidine) films modified carbon paste electrode (P‐OT/MCPE). Cyclic voltammetry and chronoamperometry techniques were used to investigate the suitability of poly(ortho‐toluidine) as a mediator for the electrocatalytic nitrite reduction in aqueous solution with various pH. Results showed that pH 0.00 is the most suitable for this purpose. In the optimum pH, the reduction of nitrite occurs at a potential about 600 mV more positive than unmodified carbon paste electrode. The catalytic reaction rate constant, (k_h), was calculated 8.68×10² M^?1 s^?1 by the data of chronoamperometry. The catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 5.00×10^?4 M–1.90×10^?2 M. Detection limit has been found to be 3.38×10^?4 M (2σ). This method has been successfully employed for quantification of nitrite in real sample.     

不饱和半夹芯式16e化合物Cp*Ir(S2C2B10H10)与邻、间位取代苯基叠氮的反应性

考虑取代基的位置和电子效应对反应体系的影响, 本文系统地研究了16e化合物Cp^*Ir(S₂C₂B₁₀H₁₀) (1)与邻、间位取代苯基叠氮的反应。研究结果表明:与邻、间位取代苯基叠氮反应均生成苯环邻位碳发生C-H 活化形成C-S 键的金属配合物。这些配合物通过核磁(¹H、¹¹B、¹³C)、红外、质谱、元素分析和单晶结构解析进行了全面地表征。在光照反应结果的基础上, 提出了形成这类产物的自由基机理。     

具有聚集荧光增强性质的双(4-二乙氨基水杨醛)缩偶氮二甲酰肼二丁基锡的合成和晶体结构

在甲醇溶液中,卡巴肼、(4-二乙氨基)水杨醛和二乙酸二丁基锡"一锅法"反应,合成了一个新颖的基于双(4-二乙氨基水杨醛)缩偶氮二甲酰肼(L)的七配位有机锡配合物[Sn(L)(n-butyl)_2]n(T)。经元素分析、IR、(1H,119Sn,13C)NMR和X射线衍射晶体结构表征,T的晶体属单斜晶系C2/c空间群,中心锡周围由双(4-二乙氨基水杨醛)缩偶氮二甲酰肼的O,N配位原子占据赤道位置和2个丁基占据顶端位置形成畸变五角双锥构型。通过烯醇式氧原子的桥联配位作用,T向一维带状无限扩展产生"竹筏状"超分子结构。配合物T在二甲基甲酰胺、四氢呋喃、乙醇、甲醇和甲苯有机溶剂及其有机溶剂-水混合物中具有强荧光发射峰,当含水量的体积分数在0～10%(V/V)时具有良好的聚集荧光增强效应,含水量大于10%(V/V)时发生荧光淬灭。     

Synthesis and structural characterization of (1,3-bis(methoxyethyl)-4,5-bis(2,4,6-trimethylphenyl)-imidazolidin-2-ylidene)chloro(1,5-cyclooctadiene)rhodium(I)

A new N-heterocyclic carbene (NHC) ligand with bulky substituents and functionalized methoxy-donor side arms complexed with Rh(I) was synthesized and characterized by elemental analysis, ¹H and ¹³C NMR, and IR spectroscopy. The crystal and molecular structure was determined by single-crystal X-ray diffraction techniques. Two carbon atoms in the cyclooctadiene ring and three ortho methyl groups have positional and orientational disorder, respectively. Rhodium has square-planar coordination geometry.     

Spectroscopical and Electrochemical Behavior of New Mixed-Ligand Cyclometalated Rh(III) Complexes

The absorption spectra, luminescence spectra, excited-state lifetimes, and electrochemical behavior of the cyclometalated [Rh(ppz)₂bpy]+^, [Rh(3-Cl-ppz)₂(bpy)]⁺, [Rh(4-NO2-ppz)₂(bpy)]⁺, [Rh(ppz)₂(biq)]⁺ and [Rh(4-NO2-ppz)₂(biq)]⁺ complexes (ppz^?, 3-Cl-ppz^?, and 4-NO₂-ppz^? are the ortho-C-deprotonated forms of 1-phenylpyrazole, l-(3-chlorophenyl)pyrazole and l-(4-nitrophenyl)pyrazole, respectively) have been investigated. The results obtained have been compared with those concerning the free protonated ligands and some previously studied mixed-ligand cyclometalated Rh(III) complexes. Luminescence originates from the lowest ligand-centered (LC) excited state, which involves the diimine ligands in all cases except for [Rh(4-NO2-ppz)₂(bpy)]⁺, where it involves the ortho-metalating ligand. s. In the absorption spectra, LC and metal-to-ligand charge-transfer (MLCT) bands, involving the diimine and/or the ortho-metalating ligands, have been assigned, and correlations between spectroscopic and electrochemical data are discussed.     

Synthesis,characterization, reactivity,and electrochemical studies of manganese(IV) complexes of bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone

Manganese(IV) complexes [Mn^IV(npah)(H₂O)₂] (1) and [Mn^IV(npah)(A)₂]?·?nH₂O (where A?=?py (2), 2-pic (3), 3-pic (4), 4-pic (5)) and Mn^IV(npah)(NN)] (NN?=?bpy (6) and phen (7)) have been synthesized from bis(2-hydroxy-1-naphthaldehyde)adipoyldihydrazone in methanol. The composition of the complexes has been established by elemental analyses. Complex 3 has been characterized by mass spectral data also. Structural assessment of the complexes has been based on data from molar conductance, magnetic moment, electronic, electron paramagnetic resonance, and infrared (IR) spectral studies. Molar conductances of the complexes in DMSO suggest non-electrolytes. Magnetic moment and EPR studies suggest +4 oxidation state for manganese in these complexes. Electronic spectral studies suggest six-coordinate octahedral geometry around the metal ions. IR spectra reveal that H₄npah coordinates to the metal in enol form. Reaction of the complexes with benzyl alcohol and SO₂ has been investigated. Cyclic voltammetric studies of the complexes have also been carried out.     

Dieisen(III)-hexacyanoferrat(II)-oxid

The title compound3 has been obtained through the action of molecular oxygen upon di-iron(II)-hexacyanoferrate(II)1 which has been prepared by thermal decomposition of ammonium hexacyanoferrate(II)2 in vacuum.2 und3 have been characterized by analytical methods andMössbauer-spectroscopy.3 and the analogous halogen compounds are semiconductors with a conductivity of 2 to 5 · 10^–5 S/cm.2 is ideally suited for the quantitative absorption of oxygen from water and organic solvents.

Herrn Prof. Dres. mult.Viktor Gutmann, Institut für Anorganische Chemie der Technischen Universität Wien, mit besten Wünschen zur Vollendung des 65. Lebensjahres gewidmet.     

Catalytic Dibenzocyclooctene Synthesis via Cobalt(III)–Carbene Radical and ortho‐Quinodimethane Intermediates

The metalloradical activation of ortho‐benzallylaryl N‐tosyl hydrazones with [Co(TPP)] (TPP=tetraphenylporphyrin) as the catalyst enabled the controlled exploitation of the single‐electron reactivity of the redox non‐innocent carbene intermediate. This method offers a novel route to prepare eight‐membered rings, using base metal catalysis to construct a series of unique dibenzocyclooctenes through selective C_carbene?C_aryl cyclization. The desired eight‐membered‐ring products were obtained in good to excellent yields. A large variety of aromatic substituents are tolerated. The proposed reaction mechanism involves intramolecular hydrogen atom transfer (HAT) to Co^III–carbene radical intermediates followed by dissociation of an ortho‐quinodimethane that undergoes 8π cyclization. The mechanism is supported by DFT calculations, and the presence of radical‐type intermediates was confirmed by trapping experiments.     

Solid Phase Extraction of Thallium(III) on Micro Crystalline Naphthalene Modified with N,N’-Bis(3-methylsalicylidene)- ortho-phenylenediamine and Determination by Spectrophotometry

A novel, simple, sensitive and effective method has been developed for preconcentration of thallium on N,N’-bis(3-methylsalicylidene)-ortho-phenylenediamine (MSOPD) adsorbent in a pH range 5.0—10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at λ＝520 nm. This method makes it possible to quantitize thallium in a range of 3.6×10－9 to 2.0×10－5 mol/L, with a detection limit (S/N＝3) of 1.42×10－9 mol/L. This procedure has been successfully applied to determine the ultra trace levels of thallium in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements, is better than 2.9%.     

SOME COMPLEXES OF AROMATIC ORTHO-BIS(METHYLTHIO)ETHERS

Abstract

The reactions of some partially fluorinated aromatic ortho-bis(methylthio)ethers with various metal ions and metal carbonyls have been examined. All the complexes formed have been characterized.     

SYNTHESIS OF 4,6-DINITROINDOLE FROM 2,4,6-TRINITROTOLUENE

1-R-4,6-Dinitroindoles 4–6 (R = H, Me, Ts) could be obtained from 2-picrylethanol 1 (readily available from TNT) via selective reduction of ortho-nitro group by N₂H₄/FeCl₃ and subsequent treatment with TsCl, to yield a key intermediate 3. This intermediate was converted to the above mentioned indoles.