Recent advances in ionic liquids: green unconventional solvents of this century: part II

Abstract

In the second part of our paper, further recent developments of ionic liquids in selected name reactions of carbonyl chemistry such as Mannich, Reformatsky, Cannizaro, Streacker, Barbier, Pechmann, etc. are described.     

Convenient stereoselective synthesis of some 3-aminosteroid scaffolds

Abstract

An efficient stereoselective synthesis 3α- and 3β-aminoandrostan-17-one and 3α-amino dehydroepiandrosten-17-one based on a Mitsunobu reaction has been developed, using azide as the ammonia equivalent. All the products were isolated in high yield.     

N-Heterocyclic carbene-Pd(II)-PPh3 complexes as a new highly efficient catalyst system for the Sonogashira cross-coupling reaction: Synthesis,characterization and biological activities

A novel series of N-heterocyclic carbene-phosphine palladium(II) complexes has been synthesized and fully characterized by IR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopies, and elemental analysis. The new N-heterocyclic carbene (NHC)-phosphine palladium(II) complexes 3a–h have been easily prepared by the reaction of the corresponding PEPPSI (pyridine-enhanced precatalyst preparation stabilization and initiation) complexes 2a–h and triphenylphosphine in dichloromethane in high yields. These complexes were applied as catalyst precursors which efficiently catalyzed Sonogashira reactions between aryl bromides and phenylacetylene to afford the corresponding products in good yields. The bulky NHC-Pd-PPh₃ complexes 3 were tested against Gram-positive and Gram-negative bacteria to study their biological activity. All the complexes exhibit antibacterial against these organisms. Investigation of the anti-acetylcholinesterase activity of the studied complexes showed that compounds 3a and 3b exhibited moderate activity at 100 μg mL^?1 and product 3b is the most active.     

Beiträge zur Chemie der Kohlensäurederivate, 3. Mitt.: Neue Synthesen von Tris(trimethylsilyl) cyanurat,N-Chlorsulfinylimid und Chlorcyan

Tris(trimethylsilyl)cyanurate (I) has been prepared in high yields by silylation of cyanuric acid with trimethylsilyl cyanide, as well as by the reaction of trichloroisocyanuric acid with trimethylsilyl cyanide or trimethylsilylsulfinylimide. The latter reactions, yielding Cl–CN and Cl–NSO resp. as the only by-products, are convenient methods for synthesizing these pseudohalogen-chloride compounds in a very pure state. Starting fromN-chlorocarbonyl isocyanateI is formed in high yields by a complex reaction with trimethylsilylsulfinylimide too. Based on IR, Raman and¹H-NMR data the O-silyl structure ofI was confirmed. The formation of products with N-silyl or N,O-silyl structure was never observed.

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2. Mitt.:E. Nachbaur, Mh. Chem.97, 361 (1966).     

Notiz zur Darstellung vonN-substituierten Aminoglycerinaldehyden

O-Benzyl-N-(benzyloxycarbonyl)-DL-serine methyl ester (1a) and peptides1 b–d with C-terminalO-benzylserine ester have been reduced with diisobutylaluminium hydride to yield the N-substituted aminoglyceraldehydes2 a–d. Using lithium tetrahydridoaluminate as the reducing agent the corresponding alcohols3 a–d have been obtained.

Herrn Dr.Albert Groß (Fa. Kulzer) zum 60. Geburtstag gewidmet.     

Synthesis and Characterization of Novel Stilbenophanes: the Smallest Members of this Class of Compounds

The synthesis, properties and energy-optimized structure of stilbenophanes 1a–3a are reported. ¹H NMR spectroscopy of 1a shows it contains vinylic protons (unlike larger stilbenophanes), which appear as two doublets showing its unexpected configuration. Protons of the methylene bridge of 1b are also observed at different chemical shift, showing that they are diastereomeric protons. It is also found that the stereochemical outcome of the intramolecular McMurry reaction is strongly influenced by the length of the alkyl bridge.     

NC Palladacycles and C,C-chelating phosphorus ylide complexes: synthesis,X-ray characterization,and comparison of the catalytic activity in the Suzuki-Miyaura reaction

Six secondary amine palladacycles bearing monodentate ligands (1a, 2a), 1,2-bis(diphenylphosphino)ethane (dppe) and 1,3-bis(diphenylphosphino)propane (dppp) containing bridging and bidentate ligands (1b, 2b–d), and four C,C-type phosphorus ylide complexes containing thiourea (tu) (3a), phenyl isothiocyanate (4a), and bridging and terminal azide groups (5 and 5a) have been synthesized. Resulting complexes have been characterized by elemental analyses, IR, ¹H-, ¹³C{¹H}-, and ³¹P{¹H}-NMR spectroscopy with single crystal X-ray structure determination of 1a and 2a. The Pd in 1a and 2a occupies the center of a slightly distorted square planar environment formed by C_aryl, N_amine, N_pyridine, and Cl. The catalytic efficiency of complexes showed that in most cases, amine palladacycles display better catalytic activities than the phosphorus ylide Pd(II) complexes. Comparison between bidentate and bridging dppe complexes showed that dppe-bridged dimer 2d has higher catalytic activity than dppe bidentate complex.     

Dinuclear vanadium complexes with rigid phenylpolycarboxylate ligands: synthesis,structure, and catalytic bromination reaction with potential detection of hydrogen peroxide

Vanadium complexes (VO)₂(2,2′-bipy)₂(bta)(H₂O)₂ (1) and (VO)₂(1,10-phen)₂(bta)(H₂O)₂ (2) (H₄bta?=?1,2,4,5-benzenetetracarboxylic acid, 2,2′-bipy?=?2,2-bipyridine and 1,10-phen?=?1,10-phenanthroline) have been synthesized by the reaction of V₂(SO₄)₃, H₄bta, 2,2′-bipy (for 1) and 1,10-phen (for 2) by hydrothermal methods. The complexes were characterized by elemental analysis, IR, UV–vis, thermogravimetric analyses, and single-crystal X-ray diffraction. Structural analyses indicate that 1 and 2 are both VO-bta-N-heterocycle system complexes. The central vanadium is coordinated by N₂O₄ donors to form a distorted octahedral geometry. The complexes exhibit catalytic bromination activity in a single-pot reaction with conversion of phenol red to bromophenol blue in a mixed solution of H₂O-DMF at 30?±?0.5?°C with pH 5.8, indicating that they can be considered as a functional model of vanadium-dependent haloperoxidases. The practical application of H₂O₂ detection has also been studied.     

Microwave-Promoted Syntheses of Pyridine Carboxamides and tert-Carboximides from Novel 6-Acetylpyridine-2-carboxylic Acid

A novel 6-acetylpyridine-2-carboxylic acid (4) was obtained occasionally during the synthesis of asymmetric ethyl 6-acetylpyridine-2-carboxylate (3) from 2,6-dipiclinic acid (1). Compounds 3 and 4 could transform mutually under some specific conditions. Two reactions of distinctive types occurred when they reacted with the aromatic amines as precursors, due to different functional groups on the 2-position of pyridine in the molecules of 3 and 4: one was Schiff base condensation and the other was an amidation reaction. From the latter reaction, two series of new compounds, pyridine carboxamides (5a–d) and pyridine tert-carboximides (6a–h), resulted. The relevant reaction mechanism is discussed in detail.     

Synthesis of New Potential NMDA Antagonist Based on Acylphosphonate Derivatives

Abstract

In recent years intensive pharmacological research is focused on the N-methyl-D-aspartate (NMDA) receptor, which has been implicated in normal neuronal hnctioning, including excitatory synaptic transmission, as well as in the pathologies of the central nervous system such epilepsy, Alzheimer and Parkinson's disease, and neurodegeneration following a stroke.     

Bis(oxamato)palladate(II) complexes: synthesis,crystal structure and application to catalytic Suzuki reaction

New bis(oxamato)palladate(II) complexes, [Pd(H₂O)₄][Pd(2,6-Me₂pma)₂]·2H₂O (1), (n-Bu₄N)₂[Pd(2,6-Me₂pma)₂]·2H₂O (2a), and (n-Bu₄N)₂[Pd(2,6-Me₂pma)₂]·2CHCl₃ (2b) (2,6-Me₂pma = N-2,6-dimethylphenyoxamate and n-Bu₄N⁺ = tetra-n-butylammonium), have been synthesized and the structures of 1 and 2b characterized by single-crystal X-ray diffraction. Complex 1 is a double salt constituted by tetraaquapalladium(II) cations and bis(oxamato)palladate(II) anions interlinked by hydrogen bonds. The palladium(II) ions in 1 are four-coordinate with two oxygens and two nitrogens from two fully deprotonated oxamate ligands (anion), and four water molecules (cation) building centrosymmetric square-planar surroundings. Centrosymmetric bis(oxamato)palladate(II) anions occur in 2b as in 1, the charge balance in this compound being ensured by the bulky n-Bu₄N⁺. The catalytic role of 1 and 2a for the Suzuki reaction has been investigated by using a series of aryl iodide/bromide derivatives in the conventional organic medium dimethylformamide. The tetraaquapalladium(II) unit in 1 appears to be active in the catalytic Suzuki cross-coupling reactions, but it readily decomposes to inactive palladium black.     

METALLAPHOSPHENES AND DIPHOSPHENES

Abstract

Transient metallaphosphenes (rbnd2;M[dbnd]P[sbnd]) have been obtained by exchange reactions between disilylphosphines and organometaldihalides (M = Ge, Sn), or by thermolysis of 2-metallaphosphetanes (M = Si, Ge). They are characterized by trapping reactions with strained heterocycles. The first stable germaphosphene 12 has been synthesized by dehydrohalogenation from the parent halogermylphosphine and isolated in form of orange crystals. It is very reactive toward compounds with active hydrogen.

Transient diphosphenes ([sbnd]P[dbnd]P[sbnd]) have been prepared by the same type of exchange reactions between disilylphosphines and dichlorophosphines and characterized by trapping reactions on dienes. The second stable diphosphene 18 has been obtained by addition of t-BuLi on trisyldichlorophosphine. Its structure has been determined by X-ray diffraction and some aspects of its reactivity are described. The reaction of bisyltrichlorogermylphosphine with DBU affords the new stable and potentially reactive diphosphene 30.     

A Novel,Convenient Synthesis of the 3‐O‐β‐D‐ and 4′‐O‐β‐D‐Glucopyranosides of trans‐Resveratrol

Abstract

trans‐Resveratrol‐3‐O‐β‐D‐glucupyranoside (trans‐piceid, 2) and trans‐resveratrol‐4′‐O‐β‐D‐glucupyranoside (trans‐resveratroloside 3) are the naturally occurring O‐glucoside conjugates of the polyphenolic stilbenoid trans‐resveratrol 1. Recently, attention has been drawn towards the interesting biological properties of the glucoside conjugates 2 and 3 as well as those of the aglycone 1. The fact that only limited quantities can be obtained by extraction from natural sources has prompted the development of novel syntheses of 2 and 3, based on a convergent Heck‐coupling strategy, which now conveniently allows for the preparation of multi‐milligram to gram quantities of each.     

A novel one-pot three-component synthesis of benzofuran derivatives via Strecker reaction: Study of antioxidant activity

Abstract

A three-component Strecker-type reactions was applied for the synthesis of benzofuran derivatives through the reaction of 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone (euparin), primary amines and trimethylsilyl cyanide (TMSCN) in the presence of catalytic amount of ZnO-nanorods (ZnO-NR) and piperidine in acetonitrile at room temperature. The method has proved to be synthetically simple, and effective with high atom economy and yield. The catalyst also revealed significant reusability. Moreover, the antioxidant activity and free radical scavenging capacity of the newly synthesized such as 4a, 4c, 6a and 6c was screened using free radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays and compared with hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ). These compounds exhibit good DPPH radical scavenging and ferric reducing antioxidant power (FRAP) assays.     

Fluorescence Lifetimes: Effect of Precision of Relaxation Times from Fluorescence Depolarization Data

Abstract

The fluorescence lifetime τ enters into the Perrin-Weber equation used to determine rotational relaxation times of proteins by the steady-state depolarization method. If is either too short or too long, the relaxation time cannot be measured with precision. With reasonable assumptions as to photometric precision, it has been possible to compute the precision of relaxation time assays for different lifetime:relaxation time ratios, thus also determining the “optimum” lifetimes for different systems. These results provide a basis for designing experiments requiring optimal conditions, and also provide insight into the amount of allowable deviation from optimal conditions. The short lifetimes of intrinsic protein fluorescence can often be used to determine the global relaxation rate of the macromolecule with acceptable precision.     

Ruthenium-Catalyzed Coupling Reaction of Benzylic Halides

Abstract

Reported herein is a novel method on dechlorination coupling reaction of halides by using RuCl₂(PPh₃)₃ catalyst under a hydrogen atmosphere with benzene as the solvent, which affords alkanes in excellent yields.     

Oxidationsreaktionen am 1-(3,3-Dimethyl-5-norbornen-2-yl)ethanon und ein neuer Zugang zuendo-konfigurierten Isocamphanderivaten

The synthesis of some new compounds with the isocamphane skeleton obtained by oxidation reactions on the bicyclic ketone3 and its derivatives is described. Some possible routes to theendo-configurated camphenilanic acid (2) have been explored which yet have to be improved to furnish better yields. Separation of mixtures of the acids1 and2 failed. Carboxylation of camphenilone yielded only theexo-configurated isocamphenilanic acid (1).2, however, an important starting material for the preparation ofendo-configurated isocamphane derivatives, can be obtained easily with high yields and sterically pure by oxidation of camphene with H₂O₂/HCOOH. Thus a cheap, one-step method for the preparation of pure2 even in larger quantities is introduced.

Auszugsweise vorgetragen auf der 3. Wissenschaftlichen Tagung der Österreichischen Pharmazeutischen Gesellschaft am 18. Oktober 1982 in Innsbruck.     

Efficient Synthesis of New Nucleoside Analogues with a Methylenecyclobutane Unit

Synthesis of eight nucleoside analogues 4–11 with a methylenecyclobutane unit is described. Wittig reaction with 2‐hydroxymethylcyclobutanone 12 gave a mixture of Z (13) and E (14) derivatives, which was separated before functional modifications. The heterocyclic moieties were introduced via a Mitsunobu reaction either on the saturated chain or on the unsaturated chain. When adenine was used in this reaction, only the N‐9 substitution products were obtained. Removal of the protecting groups provided the target products.     

Studies on the Catalysis of Ene Reactions by Lithium Perchlorate in Different Solvents

Abstract

The catalytic effect of lithium perchlorate on ene reaction of cis-cyclooctene with diethyl azodicarboxylate, 4-phenyl-1,2,4-triazoline-3,5-dione and the metallo-ene reaction of diallyldibutyltin with diethyl azodicarboxylate has been studied in different solvents like acetonitrile, acetone, diethyl ether, dimethylformamide and ethyl acetate.     

Biphenyl Macrolactams as Colorimetric Sensors for Anions through Displacement Reactions

Macrocyclic ligands 1–3 can be used as colorimetric sensor for different anions following the displacement approach. The intense colour of the 4-nitrophenolate anion in MeCN solutions that disappears upon complexation with the ligands is reinstated after the addition of specific anions. The influence of both substituents in the biphenyl moiety and size of the cavity in sensing has been considered. X-ray diffraction studies of ligand 2 are also included.