The novel approach to indole alkaloids by using Pd(II)-catalyzed cyclization

The synthesis of indole skeleton by using Pd(II)-catalyzed cyclization of the urethane has been achieved. The urethanes with allylic alcohol were converted into vinyl indolines in good yield. The vinyl indoline was transformed into some intermediates of indole alkaloids.     

Pd(II)-catalyzed coupling-cyclization reaction of o-ethylnylphenylphosphonamides monoesters with allyl halide

4-Allyl-phosphaisoquinolin-1-ones were synthesized by palladium-catalyzed coupling-cyclization of o-ethynylphenylphosphonamide monoethyl esters with allyl halides with high regioselectivity and good yields. The synthesized 4-allyl-phosphaisoquinolin-1-ones show bioactivity as inhibitor of MCH-1R.     

Pd(II)-catalyzed enantioselective intramolecular oxidative amination utilizing (+)-camphorsulfonic acid

An enantioselective Pd(II)-catalyzed intramolecular oxidative amination reaction was developed utilizing the commercially available chiral X-type ligand (1S)-(+)-camphorsulfonic acid. The Wacker-type cyclization produced chiral indoline products with enantioselectivies up to 45% ee. Electronic structure calculations employing density functional theory support a trans-aminopalladation mechanism.     

Pd(0) or Pd(II)-catalyzed ring-opening reactions of benzylidene- and alkylidenecyclopropyl ketones and aldehydes

Pd(0) catalyzed reactions of methylenecyclopropyl carbonyl compounds afforded a convenient method for the synthesis of conjugate (E,E)-1,3-diene derivatives 2 in good to excellent yields. Moreover, we also found that Pd(II)-catalyzed reactions of methylenecyclopropyl carbonyl compounds with water gave 1,5-diketones in good to high yields via a carbene-palladium intermediate. The plausible reaction mechanisms have also been provided on the basis of control and ¹⁸O-labeling experiments.     

Spectral and photophysical properties of mono and dinuclear Pt(II) and Pd(II) complexes: An unusual emission behaviour

Eight mononuclear complexes of the formula [M(N-N)(DHB)] and two binuclear complexes of the formula [M₂(BPY)₂(THB)] where M = Pd(II) or Pt(II), N-N = 2,2′-bipyridine (BPY), 2,2′-biquinoline (BIQ), 4,7-diphenyl-1,10-phenanthroline (DPP), 1,10-phenanthroline (PHEN); DHB = dianion of 3,4-dihydroxybenzaldehyde and THB = tetraanion of 3,3′,4,4′-tetrahydroxy benzaldazine were prepared and their electrochemical, spectral and photophysical properties were examined. These complexes were characterized by chemical analysis, IR and proton NMR spectroscopy. A detailed study on the absorption spectroscopy of these complexes was made. These complexes were found to show a low-energy solvatochromic ligand-to-ligand charge-transfer (LLCT) band. The electronic energies of these bands have been analyzed and compared with electrochemical data. Emission behaviour of the complexes of the series, [Pt(N-N)(DHB)], [Pt(N-N)(DHBA)] where DHBA is the dianion of 3,4-dihydroxybenzoic acid and [Pt₂(BPY)₂(THB)] was also investigated. These platinum complexes were found to emit from a low-energy state at low temperature and a high-energy state at room temperature. Photophysics of these complexes is also discussed.     

Nickel(II)-catalyzed carbon-carbon bond formation reaction of functionalized organozinc reagents with aromatic aldehydes

In the presence of a silylating reagent and catalytic amount of Ni(acac)₂, organozinc halides reacted with aromatic aldehydes to give the corresponding dialkylation products in good to excellent yields under mild conditions.     

Combining enabling techniques in organic synthesis: solid-phase-assisted catalysis under microwave conditions using a stable Pd(II)-precatalyst

The catalytic activity of a 2-pyridinealdoxime-based Pd(II)-complex covalently anchored via the oxime moiety to a glass/polymer composite material was evaluated in Suzuki-Miyaura cross-coupling reactions of aryl and heteroaryl halides, including arylchlorides, with aryl and heteroaryl boronic acids both under thermal as well as microwave irradiating conditions in water. The stability and reusability of this Pd-precatalyst is part of the present study.     

Pd/C: A Recyclable Catalyst for Cyanation of Aryl Halides with K4[Fe(CN)6]

Aryl nitriles have been prepared from the corresponding aryl halides with potassium hexacyanoferrate(II) using Pd/C as a catalyst. No ligand or cocatalyst is required. This protocol also avoids the use of highly toxic alkali cyanides. Furthermore, the catalyst can be recycled via simple filtration and washing sequences.     

Complex formation reactions between [Pd(piperazine)(H2O)2]2+ and biorelevant ligands: synthesis and equilibrium constants

[Pd(pip)Cl₂], [Pd(pip)(cbdca)] ? 2H₂O, and [Pd(pip)(malonate)] ? 2H₂O complexes were synthesized and characterized, where pip is piperazine and cbdca is cyclobutanedicarboxylate. The stoichiometry and stability of the complexes formed between [Pd(pip)(H₂O)₂]²⁺ and various biologically relevant ligands (amino acids, peptides, DNA constituents, and dicarboxylic acids) were investigated at 25°C and 0.1 M ionic strength. The stability constant of the complexes formed in solution was determined and the binding centers of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated.     

Kinetics and mechanism of electroreduction of Pd(II) complexes

The kinetics and mechanism of processes of reduction of Pd(II) complexes with a number of inorganic (NH₃ , Cl^– , etc.) and organic (ethylenediamine, glycine, -alanine, etc.) ligands on a dropping-mercury electrode and a Pd electrode in solutions with various concentrations of ligands, hydrogen ions, and supporting electrolytes are reviewed. The nature of electrochemical and chemical steps of processes of reduction of various complexes of Pd(II) is discussed.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1494–1502.Original Russian Text Copyright © 2004 by Kravtsov.     

Fluorinated Pd(II)-1,3,5-triketonates: synthesis and molecular structure

Several new mononuclear complexes of Pd(II) have been prepared from perfluorobutyl substituted 1,3,5-triketones (containing linear and carbocycle backbones) and perfluoroheptanoyl cyclohexanone. 1,3-Diketones formed a mixture of trans- and cis-forms, whereas 1,3,5-triketones gave trans-complexes exclusively. The enolization of the non-bonded carbonyls in this case depends on the nature of substituents at positions 2 and 4 of the 1,3,5-triketone moiety. The molecular structure of one triketonate complex was confirmed by X-ray single crystal investigation.     

Application of Walphos Ligand in the Pd(0)-Catalyzed Asymmetric Allylic Alkylation Reaction

One relatively unexploited commercial ligand, Walphos 1, was tested in the Pd(0)-catalyzed asymmetric allylic alkylation using rac-1,3-diphenyl propenyl acetate and rac-1-acetoxycyclohexene as substrates, methyl malonate as nucleophile, and a variety of Pd precatalysts under standard conditions. The conversions and enantioselectivities were generally good, with the greatest substrate conversion of 99% and a greatest ee of 70%. With the latter cyclic substrate, an enantioselectivity of 98% was obtained, but the conversions were all poor (15–33%).     

Five-membered ring chelate complexes of Ni(II), Pd(II) and Pt(II) derived of di-(2-pyridyl)-N-ethylimine

Cis-diaquobis{di-(2-pyridyl)-N-ethylimine}nickel(II) chloride (2) was obtained from the reaction of di-(2-pyridyl)-N-ethylimine (1) and [NiCl₂dppe] [dppe = cis-1,2-bis(diphenylphosphino)ethylene] in a 2:1 ratio in hot acetonitrile. Cis-dichloro{di-(2-pyridyl)-N-ethylimine}palladium(II) (3) and cis-dichloro{di-(2-pyridyl)-N-ethylimine}platinum(II) (4) complexes were obtained from the reaction of MCl₂ (M = Pd, Pt) and (1) in equimolar ratio in hot acetonitrile. Compounds 1–4 were characterized by IR spectroscopy, elemental analysis, and mass spectrometry; the complexes 3 and 4 were characterized in solution by NMR. In addition, solid state structures of compounds 1–4 were determined using single crystal X-ray diffraction analyses. X-ray diffraction data of the complexes 3 and 4 showed a distorted square planar local geometry at palladium and platinum atoms with the chlorine atoms in a cis-coordination; in 2 a local octahedral geometry at nickel atom was observed. Complexes 3 and 4 are arranged as dimers with a M?M distance of 3.4567(4) Å (M = Pd) and 3.4221(4) Å (M = Pt), respectively; 2 consists of units linked by intermolecular hydrogen bonding.     

Efficient palladium(II)-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives

An efficient Pd(OAc)₂-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives is described. It represents a facile and practical methodology to prepare bis-5,5′-thiazole (oxazole)-4,4′-dicarboxylic derivatives in good to excellent yields. This protocol tolerates a series of substitutions on the thiazole (oxazole) rings, including alkyl, carbonyl, and electron-withdrawing/donating group substituted phenyl groups.     

SYNTHESIS AND STRUCTURE OF Pd(II) COMPLEXES OF 1,2,3-TRIPHENYLGUANIDINE

Abstract

The formation of two complexes by reaction of [PdCl₄]^2- with 1,2,3-triphenylguanidine (PhNH)₂C=NPh under different metal/ligand ratios has been observed and the structure of the complex [(1,2,3-triphenylguanidine)₂PdCl₂] has been determined by X-ray diffraction methods. The ligands are coordinated as neutral monodentate molecules to the metal centre through their imine nitrogen atoms. The second Pd(II) complex is [Pd(1,2,3-triphenylguanidine)₄]²⁺ and was isolated by precipitation with ClO^? ₄.     

Hydration Structure and Dynamic Properties of the Square Planar Pt(II) Aquaion Compared to the Pd(II) Case

This work examines, by means of classical Molecular Dynamics simulations, the hydration of a square planar hydrate, [Pt(H₂O)₄]²⁺, focussing the attention on the structure and dynamics adopted by water molecules in the regions above and underneath the molecular plane. Results obtained are compared with those previously derived for the case of the [Pd(H₂O)₄]²⁺ where the concept of meso-shell was introduced to define this axial region [Martínez et al. (J Phys Chem B 108:15851, 2004)]. Specific ab initio intermolecular potentials describing the interaction between the ion and the solvent have been developed following the statistical implementation of the hydrated ion concept for the case of a planar aquaion. A meso-shell is characterized by a peak in the Pt–O RDF centered at 2.95 Å which integrates to two water molecules; the mean residence time for these molecules is in the range 1–7 ps. The vibrational frequency associated to the dynamic variable defined from the distance meso-shell water molecule-cation is used to quantify the linkage degree of the water molecule in this shell. The meso-shell in Pt(II) is more labile than in the Pd(II) case, whereas the first and second hydration shells of both cations are highly similar. The observed differences in meso-shell are discussed in relation with the mechanistic interpretation of the solvent exchange at the first hydration shell.     

Ru(II)催化有机叠氮与炔反应机理的理论研究

采用密度泛函理论, 对在Ru(II)催化剂存在下, 有机叠氮化合物和末端炔的反应机理作了深入理论研究. 在B3LYP/LANL2DZ水平上, 对该反应体系中势能面各驻点的几何构型进行了全优化计算, 并经振动频率分析确定了过渡态和中间体, 通过内禀反应坐标(IRC)的计算, 确认了反应物、中间体、过渡态和产物的相关性. 对多个反应通道的协同反应以及分步反应进行了研究. 结果表明: 协同反应通道Ic和分步反应通道IIc是反应能垒较低的反应通道, 活化自由能较其它反应通道低, 有利于1,5-二取代1,2,3-三唑的生成, 具有特定的区域选择性, 与实验结果吻合.     

Six-membered ring chelate complexes of Pd(II) and Pt(II) derived from di-(2-pyridyl)pyrimidin-2-ylsulfanylmethane

Cis-[MLCl₂] complexes of di-(2-pyridyl)pyrimidin-2-ylsulfanylmethane ligand (L), where M = Pd (1), and M = Pt (2) have been synthesized. Reaction of 1 with L in presence of Na[BF₄] and hot acetonitrile produced the complex [PdL₂](BF₄)₂ (3). Complexes 1-3 and ligand L have been characterized by elemental analyses, IR and NMR spectroscopy. Crystal structures of 1, 3 and L were determined by single crystal X-ray diffraction analyses, showing nonplanar structures with the pyridinic rings twisted around the bridging carbon and the ipso carbon bonds. 1 and 3 displayed a bidentate coordination of L to the palladium atom with the formation of six-membered chelate rings, where the local geometry at palladium atom was distorted square planar. In 3 the palladium atom was coordinated to two dipyridyl ligands through two of the pyridinic nitrogen atoms to form a cationic complex stabilized by two tetrafluoroborate counter-ions.     

Palladium(II)-catalyzed tandem annulation reaction of o-alkynylbenzoates with methyl vinyl ketone for the synthesis of isocoumarins

A palladium(II)-catalyzed highly regioselective tandem reactions of o-alkynylbenzoates with methyl vinyl ketone for the synthesis of isocoumarins was developed. It is a convenient, mild and environmentally benign reaction with moderate to high yield. The reaction is initiated by the Pd(II) species and regenerate the Pd(II) species to complete the catalytic cycle without the necessity of a redox system.     

General synthesis of (1-substituted-1H-1,2,3-triazol-4-ylmethyl)-dialkylamines via a copper(I)-catalyzed three-component reaction in water

A copper(I)-catalyzed three-component reaction to form (1-substituted-1H-1,2,3-triazol-4-ylmethyl)-dialkylamines based on the Huisgen cycloaddition using amine, propargyl halide and azide in water was proposed. The process showed considerable synthetic advantages in terms of high atom economy, low environmental impact, atmospheric oxygen, wide substrate scope, mild reaction condition and good yields.