Good Yields (good + yield)

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Good Yields

  • very good yield

  • Selected Abstracts

    Preparation of Primary Arylamines via Arylzinc Chlorides in Good Yields.

    CHEMINFORM, Issue 32 2006
    Tahir Daskapan
    Abstract ChemInform 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. [source]

    Further Studies on the Synthesis of meso -Tetraarylazuliporphyrins under Lindsey,Rothemund Reaction Conditions and Their Conversion into Benzocarbaporphyrins

    Timothy D. Lash
    Abstract Azulene has been shown to react with pyrrole and a series of aromatic aldehydes in the presence of boron trifluoride etherate to give meso -tetraarylazuliporphyrins 6. Good yields of azuliporphyrins were obtained for benzaldehyde, 4-chlorobenzaldehyde, 4-bromobenzaldehyde, and 4-iodobenzaldehyde, and under dilute conditions p -tolualdehyde gave respectable yields. In each case, substantial amounts of meso -tetraarylporphyrins were also formed and a minor fraction of carbaporphyrin by-products could be detected, but otherwise no other macrocyclic products could be identified. 4-Nitrobenzaldehyde gave relatively poor yields of the corresponding azuliporphyrin, while p -anisaldehyde only gave trace amounts of product. Pentafluorobenzaldehyde gave variable results, although in this case a large number of additional by-products were identified including N -fused pentaphyrin, hexaphyrin, and higher order porphyrinoids, but no expanded azulene-containing macrocycles could be detected. Azuliporphyrins undergo reversible nucleophilic substitution on the seven-membered ring with pyrrolidine, benzenethiol, hydrazine, or benzylamine to give carbaporphyrin adducts. This property appears to facilitate an oxidative ring contraction of azuliporphyrins 6 with tert -butyl hydroperoxide in the presence of potassium hydroxide to produce mixtures of benzocarbaporphyrins 19 and 20. Tetraaryl-benzocarbaporphyrins exhibit slightly reduced diatropic ring currents compared to their meso -unsubstituted counterparts, although their UV/Vis spectra are very porphyrin-like and exhibit strong Soret bands near 450 nm. The benzocarbaporphyrins undergo reversible protonation to give monocationic and dicationic species. The latter involves C -protonation to generate an internal CH2 within the macrocyclic cavity. X-ray crystallography of tetraphenylbenzocarbaporphyrin 19a confirms that the preferred tautomer has the two NHs on either side of the indene subunit, in agreement with previous theoretical and spectroscopic studies. In addition, the presence of phenyl substituents at the 5,20-positions was found to tilt the indene moiety substantially by 27.4(1)° relative to the [18]annulene substructure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Palladium-Catalysed Direct Arylation of Heteroaromatics Bearing Unprotected Hydroxyalkyl Functions using Aryl Bromides

    Julien Roger
    Abstract Heteroaromatics bearing unprotected hydroxyalkyl functions can be arylated using aryl or heteroaryl bromides, via palladium-catalysed carbon-hydrogen bond activation/arylation. Good yields were generally obtained using 0.01,0.5,mol% of the air-stable palladium acetate complex as the catalyst. The nature of the base was found to be crucial for the selectivity of this reaction. Potassium acetate led to the direct arylation products whereas caesium carbonate led to the formation of the ether. This procedure is certainly more atom-economic than other methods for the preparation of such compounds, as no protection/deprotection sequence of the hydroxyalkyl function and no preparation of an organometallic derivative is required. [source]

    Synthesis ,-aminonitrile through anodic cyanation of N -benzylpiperidine

    Ping Zhao
    Six-membered cyclic ,-aminonitrile has been prepared from anodic cyanation of N -benzylpiperidine. Good yields of ,-aminonitriles could be obtained through potentiostatic electrolysis under different conditions. The results also explain why high yield ,-aminonitriles could not be obtained under constant current electrolysis. [source]

    Microwave-accelerated synthesis of psychoactive deuterated N,N -dialkylated-[,,,,,,, -d4]-tryptamines

    Simon D. Brandt
    Abstract A large number of N,N -dialkylated tryptamines are known to induce psychoactive effects in humans. This has resulted in their increased attention within clinical and forensic communities. Deuterated tryptamines are ideal for use as internal standards during MS bioanalysis or of use in biochemical NMR studies. The present study reports on a microwave-enhanced synthesis of 22 N,N -dialkylated-[,,,,,,, -d4]-tryptamines via the reduction with lithium aluminium deuteride of glyoxalylamide precursors obtained by the procedure of Speeter and Anthony. Syntheses were carried out using a single-mode system under elevated pressure conditions where anhydrous tetrahydrofuran was used as the solvent at 150°C. Good yields were obtained within 5,min. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Synthesis of tritium labelled zaleplon

    V.P. Shevchenko
    Abstract The reaction conditions for the incorporation of tritium into zaleplon have been investigated. The methods studied were the catalytic isotope exchange reaction with tritium gas and catalytic isotope exchange reaction with tritiated water. The results showed that the latter method was the method of choice giving a compound with a higher specific activity and a better yield. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Straightforward Strategy for the Stereoselective Synthesis of Spiro-Fused (C-5)Isoxazolino- or (C-3)Pyrazolino-(C-3)quinolin-2-ones from Baylis,Hillman Adducts by 1,3-Dipolar Cycloaddition and Reductive Cyclization,

    Virender Singh
    Abstract A straightforward and general approach for the stereoselective synthesis of spiro-fused (C-5)isoxazolino- or (C-3)pyrazolino-(C-3)quinolin-2-ones from the adducts offorded from the Baylis,Hillman reaction of 2-nitrobenzaldehyde and ethyl acrylate by sequential 1,3-dipolar cycloaddition and reductive cyclization is presented. It was found that the reductive cyclization of the isoxazoline derivatives proceeded efficiently in the presence of In/HCl, whereas similar reductions of pyrazolines gave better yields when carried out in the presence of an Fe/AcOH mixture. However, similar attempts employing the Baylis,Hillman adduct of 2-nitrobenzaldehyde and methyl vinyl ketone did not yield the desired compounds.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Neutral Group-IV Metal Catalysts for the Intramolecular Hydroamination of Alkenes

    Carsten Müller
    Abstract A detailed comparison of the group-IV metal catalysts Ti(NMe2)4, Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 in the intramolecular hydroamination of amino alkenes is presented. Among these catalysts, the benchmark catalyst Ti(NMe2)4 is the most active in the formation of pyrrolidines. A comparison between Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 suggests that in the synthesis of pyrrolidines, Zr complexes show the highest catalytic activity of the group-IV metal catalysts. Although Ind2TiMe2 - and the Ind2ZrMe2 -catalyzed formation of a pyrrolidine is first-order in the concentration of the substrate, the corresponding Ti(NMe2)4 -catalyzed cyclization is second-order in the concentration of the substrate. The results obtained for the formation of piperidines catalyzed by Ti(NMe2)4, Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 suggest that for these reactions, Ti catalysts show increased catalytic activity compared with the corresponding Zr catalysts. Unfortunately, the formation of aminocyclopentane side-products by C,H activation processes is a severe drawback of the Ti catalysts. The corresponding side-products are not formed in Ind2ZrMe2 - and Ind2HfMe2 -catalyzed reactions. However, the former catalyst gives better yields of the desired piperidine products. In contrast to the results obtained for the synthesis of pyrrolidines, the formation of a piperidine is zero-order in the concentration of the substrate for the indenyl catalysts Ind2TiMe2 and Ind2ZrMe2, and first-order for the homoleptic catalyst Ti(NMe2)4. Interestingly, Ind2TiMe2 is able to catalyze a slow hydroamination of an N -methylated amino alkene, whereas the homoleptic complex Ti(NMe2)4 as well as Ind2ZrMe2 and Ind2HfMe2 do not catalyze the same reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Effect of Altitude on Energy Exchange Characteristics of Some Alpine Medicinal Crops from Central Himalayas

    S. Chandra
    Abstract To explore the conservation and cultivation of endangered alpine medicinal crops at comparatively lower altitudes, a study on variations in morphological parameters and energy exchange characteristics was conducted on five herbaceous medicinal crops from the alpines of Central Himalayas. Plants of same age were selected from the alpine medicinal crop nursery, Tungnath (3600 m), and were planted at the nurseries at 2100 and 550 m altitudes. After well acclimatization at lower altitudes, plants were examined for morphological and energy exchange studies during their active growth period. The energy balance sheet of these plant species indicates that most of the energy absorbed by the leaves dissipates by re-radiation, transpiration and thermal conductance across leaf surfaces. All species maintained leaf temperature below the surrounding air temperature at all altitudes and therefore gained energy by convection of heat as well as by boundary layer thermal conduction. Leaf-to-air temperature difference, gain of energy by convection of heat and boundary layer thermal conduction was maximum at an altitude of 2100 m in all the species. Boundary layer thermal conductivity, boundary layer thickness, thermal conductivity of the leaf and therefore, total energy absorbed by the leaves of these species increase significantly with decreasing altitude. Leaf thickness significantly decreases with decreasing altitude, which in turn enhances total energy absorption (r = ,0.975, P < 0.005) of the leaves in all the species. The results indicate that all these species absorb higher amount of energy at lower altitudes, which indicates their adaptability to warm temperatures at low altitudes (up to 550 m). Therefore, these species can be cultivated at relatively lower altitudes. However, a proper agronomic methodology needs to be developed for better yields. [source]

    Synthesis of N -Acetyl-,-aminobutyric Acid via Amidocarbonylation: A Case Study

    Dirk Gördes
    Abstract The synthesis of N -acetyl-,-aminobutyric acid by amidocarbonylation of propionaldehyde with acetamide in the presence of palladium catalysts is studied in detail. The influence of various reaction conditions and compositions (e.g., the co-catalysts acid and bromide) on the yield of N -acetyl-,-aminobutyric acid is shown. For the first time it is demonstrated that the palladium-catalyzed amidocarbonylations of aldehydes can be run with significantly lower halide concentrations (<30 mol,%) without a major yield decrease. While phosphine-free catalyst systems give best yields at low CO pressure, phosphine-ligated palladium catalysts lead to better yields at higher CO pressure. At low palladium loadings (<0.1 mol,%), unwanted condensation reactions of propionaldehyde become increasingly competitive. [source]

    Mononuclear cell collection in patients undergoing extra-corporeal photo-chemotherapy for acute and chronic graft-vs.-host-disease (GvHD): Comparison between COBE Spectra version 4.7 and 6.0 (AutoPBSC)

    Paolo Perseghin
    Abstract A constant improvement in the performance of blood cell separators has been observed in recent years, allowing better yields in peripheral blood stem cell collection (PBSC) either from healthy donors or for autologous purposes. Nevertheless, to our knowledge, no reports on the efficiency of mononuclear cell (MNC) collection in patients undergoing extra-corporeal photochemotherapy (ECP) for graft-vs.-host-disease (GvHD) have been published. We retrospectively investigated the efficiency of 167 MNC collections performed consecutively in 12 patients between January 1999 and June 2001 by means of the COBE Spectra version 4.7 (V 4.7) or version 6.0 (V 6.0), for 109 and 58 procedures, respectively. MNC fractional extraction (FE) was higher in the V 6.0 group compared to the V 4.7 group : 0.59 ± 0.21 vs. 0.51 ± 0.22 (P < 0.05). However, platelet contamination was lower in the products obtained with V.6.0 compared to those obtained with V.4.7: 740 ( 630 × 103/(L vs. 2,073 ( 1,429 × 103/(L (P < 0.05). Only two patients with acute GvHD, both from V 4.7 group, required post-ECP platelet transfusion. The recently released version 6.0 allowed a satisfactory MNC yield with minimal platelet contamination in patients scheduled to undergo ECP for acute or chronic GvHD. J. Clin. Apheresis 17:65,71, 2002. © 2002 Wiley-Liss, Inc. [source]

    Rapid techniques for the extraction of vitamin E isomers from Amaranthus caudatus seeds: ultrasonic and supercritical fluid extraction

    Renato Bruni
    Abstract Supercritical fluid extraction (SFE) of seeds of Amaranthus caudatus (Amaranthaceae) and the use of ultrasound as a co-adjuvant in the extraction process were compared with methods traditionally used in the extraction of tocopherols and fatty acids. The use of readily available ultrasound equipment as an adjunct to the classical methods employed for the extraction of tocols provided qualitatively acceptable results more rapidly and more economically. SFE gave quantitatively better yields in shorter times, with solvent-free extracts obtained under conditions that minimised the degradation of thermolabile components. No significant variations were observed in the profile of the fatty acids extracted from amaranth oil by SFE or other methods, thus confirming the qualitative comparability of the faster supercritical extraction with the more time-consuming classical techniques even when processed with the aid of ultrasound. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Impact of rootstock on yield and ion concentrations in petioles, juice and wine of Shiraz and Chardonnay in different viticultural environments with different irrigation water salinity

    Abstract Background and Aims: Within-site comparisons were made of rootstock effects on yield, and chloride and sodium concentrations in petioles, juice and wine of Shiraz and Chardonnay vines at sites with irrigation water salinities (ECiw) ranging from low (0.4 dS/m) to moderate-high (1.8 to 3.3 dS/m). It also compared consistency of yield performance of the various rootstocks with both scions over 8 years at one site with an ECiw of 2.1 dS/m. Methods and Results: Chardonnay and Shiraz on own roots and on Ramsey, 1103 Paulsen, 140 Ruggeri, K51-40, Schwarzmann, 101-14, Rupestris St. George and 1202 Couderc were compared. Ramsey resulted in better yields relative to most of the other rootstocks at three of the four sites for each scion. Exceptions were the low salinity site where Schwarzmann was best with Chardonnay, and Padthaway where 140 Ruggeri was best with Shiraz. Chardonnay wine chloride concentrations were similar to grape juice chloride concentrations, but Shiraz wine chloride concentrations were on average 1.7-fold higher than grape juice chloride. Conclusions: Shiraz on own roots, K51-40 and 1202C rootstocks carry some risk of accumulating unacceptable levels of chloride in grape juice and wine when the salinity of the irrigation water is at moderate to high levels. Rootstocks K51-40 (with Chardonnay and Shiraz) and potentially 101-14 (with Shiraz) should be avoided in situations of long term irrigation with moderate to high salinity water. Significance of the Study: The study identifies rootstocks with acceptable yields and grape juice chloride concentrations for potential use in regions affected by salinity. [source]

    Improved chromatographic fingerprints for facile differentiation of two Ganoderma spp.

    Chun-Mei Fu
    Abstract This paper addresses a comprehensive and comparative study of six phytochemical extraction methods for triterpenes from the fruiting body of Ganoderma spp. Quantitative analysis of extracts was performed by HPLC with photodiode array detection. In general, pressurized liquid extraction and microwave-assisted extraction under optimized conditions produce better yields, and the former also significantly reduces the total time of extraction and manipulation of a sample, as well as the amount of solvent used in comparison with conventional soxhlet, reflux, ultrasonic, and methanol,CO2 supercritical fluid extractions. Based on the improved extraction protocol, the fingerprinting profiles for two species of Lingzhi were established using the consistent chromatographic features of 12 authentic samples. Eleven common peaks of ganoderic/ganoderenic acids were identified using LC-ESI-MS-MS. These specific triterpene groups were adopted as chemical markers for Lingzhi. Using chemometric analysis, the developed fingerprinting was successfully applied to differentiate between the two species under the Ganoderma genus and is applicable as a method for quality evaluation of this valuable medicinal fungus and its related proprietary products. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Biaryls Made Easy: PEPPSI and the Kumada,Tamao,Corriu Reaction

    Michael G. Organ Prof.
    Abstract An easily employed, highly versatile Kumada,Tamao,Corriu (KTC) protocol utilizing the PEPPSI (Pyridine, Enhanced, Precatalyst, Preparation, Stabilization and Initiation) precatalysts 1 and 2 is detailed. The ease-of-use of these catalysts and the synthesis of a wide range of hindered biaryls, large coupling partners and drug-like heterocycles, in high yield, makes the PEPPSI-KTC protocol very attractive. The high reactivity of the PEPPSI system allowed a tetra- ortho -substituted heterocycle, 11 to be synthesized at room temperature for the first time using any protocol. The PEPPSI protocols also tolerated the Boc protecting group and phenols required no protection in modified conditions. A relatively large scale (10 g) reaction was also performed with no loss in performance. Furthermore, PEPPSI-IPr, 1, was compared to previously reported highly active phosphine ligands 42, 43, and 44 and was shown to result in significantly better yields under identical conditions. Finally, we demonstrated that the PEPPSI catalyst system is very adept at performing sequential KTC coupling reactions, analogous to multicomponent reactions, which allow complex polyaryl and polyheteroaryl architectures to be produced in one single operation. [source]

    Focused proteomics: Monoclonal antibody-based isolation of the oxidative phosphorylation machinery and detection of phosphoproteins using a fluorescent phosphoprotein gel stain

    ELECTROPHORESIS, Issue 15 2004
    James Murray
    Abstract We have raised monoclonal antibodies capable of immunocapturing all five complexes involved in oxidative phosphorylation for evaluating their post-translational modifications. Complex I (NADH dehydrogenase), complex II (succinate dehydrogenase), complex III (cytochrome c reductase), complex IV (cytochrome c oxidase), and complex V (F1F0 ATP synthase) from bovine heart mitochondria were obtained in good yield from small amounts of tissue in more than 90% purity in one step. The composition and purity of the complexes was evaluated by Western blotting using monoclonal antibodies against individual subunits of the five complexes. In this first study, the phosphorylation state of the proteins without inducing phosphorylation or dephosphorylation was identified by using the novel Pro-Q Diamond phosphoprotein gel stain. The major phosphorylated components were the same as described before in sucrose gradient enriched complexes. In addition a few additional potential phosphoproteins were observed. Since the described monoclonal antibodies show cross reactivity to human proteins, this procedure will be a fast and efficient way of studying post-translational modifications in control and patient samples using only small amounts of tissue. [source]

    Mono-, Bi-, Tri- and Tetranuclear Palladium(II), Copper(I), and Gold(I) Complexes of Morpholine- and N -Methylpiperazine-Functionalized Cyclodiphosph(III)azans, cis -[(tBuN-,)2(PNC4H8X)2] (X = O, NMe)

    Maravanji S. Balakrishna
    Abstract Bis(amido)cyclodiphosphazanes, cis -[(tBuN-,)2(PNC4H8O)2] (2) and cis -[(tBuN-,)2(PNC4H8NMe)2] (3) were synthesized by treating the corresponding amines with cis -[ClP(tBuN-,)2PCl] (1). The stoichiometric reactions of 2 or 3 with elemental sulfur and selenium afforded the bis-chalcogenides, cis -[(tBuN-,)2(P(E)NC4H8X)2] (X = O, E = S; 4, X = NMe, E = S; 5, X = O, E = Se; 6, X = O, E = Se; 7). The reactions of 2 or 3 with [PdCl2(SMe2)2] produced exclusively the mononuclear trans -[PdCl2{(tBuN-,)2(PNC4H8X)2}2] (X = O; 8, X = NMe; 9), whereas the reactions with [Pd(,-Cl)(,3 -C3H5)]2 afforded the bimetallic complexes [{PdCl(,3 -C3H5)}2{(tBuN-,)2(PNC4H8X)2}] (X = O; 10, X = NMe; 11) in good yield. Treatment of 2 or 3 with [AuCl(SMe2)] in 1:1 and 1:2 molar ratios yielded the mono- and binuclear complexes, [{AuCl(tBuN-,)2(PNC4H8O)2}] (X = O; 12, X = NMe; 13), [{AuCl}2{(tBuN-,)2(PNC4H8O)2}] (X = O; 14, X = NMe; 15), respectively. The PdII (8) and AuI (12) complexes were used as metallo-ligands to prepare homo- and heterometallic complexes, trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2{Pd(,3 -C3H5)Cl}2] (16), trans -[PdCl2{(tBuN-,)2(PNC4H8O)2}2(AuCl)2] (17), and [Cu(CH3CN)(,-Cl)2Cu(CH3CN){(tBuN-,)2(PNC4H8O)2}2(AuI)2](18). The crystal structures of 2, 4, 7,9, 14, 15, and 18 were established by single-crystal X-ray diffraction studies. [source]

    Salen Ligands Revisited: Synthesis and Application of a Planar Chiral "Ferro-Salen" Ligand

    Jochen Niemeyer
    Abstract Condensation of the O-protected planar chiral hydroxyferrocene carbaldehyde (Sp)- 1 with ethylenediamine, followed by deprotection gave rise to the "ferro-salen" ligand (Sp,Sp)- 3 in good yield. This scaffold was used for the preparation of a series of metal complexes [(Sp,Sp)- 4/5/6], which were subsequently applied for the Lewis acid catalyzed asymmetric trimethylsilylcyanation of benzaldehyde. [source]

    Designing the Host-Guest Properties of Tetranuclear Arene Ruthenium Metalla-Rectangles to Accommodate a Pyrene Molecule

    Nicolas P. E. Barry
    Abstract Cationic tetranuclear arene ruthenium complexes of the general formula [Ru4(p -cymene)4(N,N)2(dhnq)2]4+ comprising rectangular structures are obtained in methanol from the reaction of the dinuclear arene ruthenium precursor [Ru2(p -cymene)2(dhnq)2Cl2] (dhnq = 5,8-dihydroxy-1,4-naphthoquinonato) with pyrazine or bipyridine linkers [N,N = pyrazine, 1; 4,4,-bipyridine, 2; 1,2-bis(4-pyridyl)ethylene, 3] in the presence of AgCF3SO3. All complexes 1,3, isolated in good yield as triflate salts, have been characterised by NMR and IR spectroscopy. The interaction of these rectangular complexes with pyrene as a guest molecule has been studied in solution by various NMR techniques (1D, DOSY, ROESY). In [D3]acetonitrile, the pyrazine-containing metalla-rectangle 1 shows no meaningful interactions with pyrene. On the other hand, the 4,4,-bipyridine- and 1,2-bis(4-pyridyl)ethylene-containing metalla-rectangles 2 and 3 clearly interact with pyrene in [D3]acetonitrile. DOSY measurements suggest that, in the case of [Ru4(p -cymene)4(4,4,-bipyridine)2(dhnq)2]4+ (2), the interactions occur on the outside of the rectangular assembly, while in the case of [Ru4(p -cymene)4{1,2-bis(4-pyridyl)ethylene}2(dhnq)2]4+ (3), the pyrene molecule is found inside the hydrophobic cavity of the metalla-rectangle, thus giving rise to a host-guest system. [source]

    An Efficient Route to Group 6 and 8 Metallaborane Compounds: Synthesis of arachno -[Cp*Fe(CO)B3H8] and closo -[(Cp*M)2B5H9] (M = Mo, W)

    K. Geetharani
    Abstract Reaction of [Cp*Fe(CO)2I] (Cp* = ,5 -C5Me5) with an excess amount of BH3·thf in toluene at 75 °C or with LiBH4 at ,78 °C leads to the isolation of hydrogen-rich ferraborane arachno -[Cp*Fe(CO)B3H8] in good yield. In a similar fashion, reaction of [Cp*M(CO)3Cl] (M = Mo and W) with an excess amount of BH3·thf at 80 °C or at ,78 °C with LiBH4 yielded metallaboranes [(Cp*M)2B5H9] (M = Mo, W). Isolated yields of closo -[(Cp*M)2B5H9], (M = Mo and W), both from LiBH4 and BH3·thf, are good. All compounds were characterized in solution by IR, 1H, 11B, and 13C NMR spectroscopy and mass spectrometry and the structural types were unequivocallyestablished by crystallographic analysis of arachno -[Cp*Fe(CO)B3H8].(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Uncommon Solvent Effect in Oxidative Addition of MeI to a New Dinuclear Platinum Complex Containing a Platina(II)cyclopentane Moiety

    S. Jafar Hoseini
    Abstract The reaction of the known complex cis,cis -[Me2Pta(,-dppm)(,-SMe2)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] [dppm = bis(diphenylphosphanyl)methane] with phthalazine (NN) proceeded by replacement of the labile bridging SMe2 ligand with the bidentate N-donor ligand NN to give cis,cis -[Me2Pta(,-dppm)(,-NN)Ptb,CH2(CH2)2CcH2(Ptb,Cc)] (1) as a pale red solid in good yield. The complex was fully characterized by multinuclear (1H, 31P, 195Pt) NMR spectroscopy. The subsequent reaction of complex 1 with excess MeI gave the colorless diplatinum(IV) complex [Me3Pta(,-dppm)(,-I)2Ptb{CH2(CH2)2CcH2(Ptb,Cc)}Me], in which the bridging NN ligand is replaced by bridging iodido ligands. The reddish color of complex 1, which is due to a metal-to-ligand charge transfer (MLCT) band in the visible region, was used to monitor its reaction with MeI in the solvents acetone, CH2Cl2, and benzene. The kinetic data revealed that the reactions in nonpolar benzene or slightly polar CH2Cl2 proceeded in two steps, each following a common SN2 mechanism. In the first step, MeI attacked the platina(II)cyclopentane center rather than the dimethylplatinum(II) center, because the first center is more electron-rich than the second center. In the more polar acetone, the reaction proceeded similarly, with the exception that each step was accompanied by a solvolytic reaction, which was suggested to be responsible for the unusually slower reaction rate in acetone than in benzene or CH2Cl2. Consistently, the reaction rate in the highly polar solvent CH3CN was too slow for any meaningful measurement.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Bis(acetylido) Complexes of Ruthenium(II) Bearing Monodentate Phosphane Ligands

    Leslie D. Field
    Abstract Terminal acetylenes react with cis -RuMe2(PMe3)4 to form the bis(acetylido) complexes cis/trans -Ru(C,CR)2(PMe3)4 in good yield. The structures of trans - 2 (R = Ph), cis - 3 (R = p -C6H4 -OMe), trans - 4 (R = p -C6H4 -Me), cis - 6 (R = Me), trans - 7 (R = SiMe3) and cis - 8 (R = H) were determined by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Tagging (Arene)ruthenium(II) Anticancer Complexes with Fluorescent Labels

    Fabio Zobi
    Abstract Fluorescent (arene)ruthenium(II) complexes have been prepared by tagging a small fluorogenic reporter onto the chelating ligand of complexes of the type [(,6 -arene)RuCl(Z)]+ (Z = chelating ligand). Complexes [(,6 - p -cym)RuCl(NNO)](Cl) (2), [(,6 - p -cym)RuCl(L3)](Cl) (3) and [(,6 - p -cym)RuCl(L4)](Cl) (4) {p -cym = p- cymene, NNO = 2-[(2-aminoethyl)amino]ethanol, L3 = 2-[(2-aminoethyl)amino]ethyl-2-(methylamino)benzoate and L4 = N -{2-[(2-aminoethyl)amino]ethyl}-2-(methylamino)benzamide} were obtained in good yield from the reaction of the Ru dimer [(,6 - p -cym)RuCl2]2 (1) and the corresponding ligand. The compounds have been fully characterized and their X-ray crystal structures are reported. Compounds 3 and 4 show a photoluminescence response centered at 435 nm with partial fluorescence quenching of the fluorogenic reporters L3 and L4 upon coordination to the metal center. Species 2,4 show good solubility both in water and organic solvents. In water, 2,4 readily hydrolyze to form the aqua complexes. These are stable at acidic pH forming 10,15,% of the corresponding hydroxido complexes in buffered solution (25 mM HEPES) as the pH is raised to a physiological value (pH = 7.44). Under these conditions, 4 (but not 2 or 3) undergoes a fast pH-dependent reversible intramolecular rearrangement. Experimental data and semiempirical calculations indicate that the major species arising from this transformation is a complex with a tridentate chelating ligand following deprotonation at the nitrogen atom of the amide group. Esterase-catalyzed hydrolysis of 3 liberates isatoic acid (MIAH) and generates 2 indicating that the complex is a substrate for the enzyme. Complexes similar to 3 may have potential for esterase-activated Ru-based prodrug delivery systems.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis and Properties of Organometallic PtII and PtIV Complexes with Acyclic Selenoether and Telluroether Ligands and Selenoether Macrocycles

    William Levason
    Abstract The first series of planar dimethyl(selenoether)PtII complexes, [PtMe2L] [L = MeSe(CH2)nSeMe (n = 2 or 3), o -C6H4(CH2SeMe)2, [8]aneSe2 (1,5-diselenacyclooctane), or [16]aneSe4 (1,5,9,13-tetraselenacyclohexadecane)], have been obtained by treatment of [PtMe2(SMe2)2] with L in Et2O solution and characterised by VT 1H, 13C{1H}, 77Se{1H} and 195Pt{1H} NMR spectroscopy, electrospray MS and microanalysis. The corresponding dimethyl(telluroether)PtII complexes do not form under similar reaction conditions. The distorted octahedral [PtMe3I(L)] [L = o -C6H4(CH2SeMe)2, [8]aneSe2, [16]aneSe4 or MeC(CH2SeMe)3] form as stable complexes in good yield from reaction of PtMe3I with L in refluxing CHCl3 and have been characterised similarly. These all show bidentate selenoether coordination, with fast pyramidal inversion occurring at room temperature. The distorted octahedral coordination environment at PtIV is also confirmed from a crystal structure of [PtMe3I{o -C6H4(CH2SeMe)2}]. Rare examples of (telluroether)PtIV complexes, [PtMe3I{o -C6H4(CH2TeMe)2}] and the dinuclear [Me3Pt(,2 -I)2(,2 -MeTeCH2TeMe)PtMe3], have also been prepared and characterised similarly (and also by 125Te{1H} NMR spectroscopy). The [8]aneSe2 and [16]aneSe4 species are the first examples of alkyl PtII or PtIV complexes with (macro)cyclic selenoether coordination. Halide abstraction (TlPF6) from [PtMe3I(,2 -[16]aneSe4)] affords [PtMe3(,3 -[16]aneSe4)]PF6; a rare example of a cationic PtIV selenoether. The (diselenoether)PtII complexes undergo oxidative addition of MeI to yield the corresponding PtIV species [PtMe3I(diselenoether)]. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Synthesis and Reaction of MnII Iodides Bearing the ,-Diketiminate Ligand: the First Divalent Manganese N-Heterocyclic Carbene Complexes [{HC(CMeNAr)2}MnI{C[N(iPr)CMe]2}] and [{HC(CMeNAr)2}MnNHAr{C[N(iPr)CMe]2}] (Ar = 2,6- iPr2C6H3)

    Jianfang Chai
    Abstract The manganese mono-iodide [HC(CMeNAr)2]MnI(THF) (Ar = 2,6- iPr2C6H3) (3) was prepared in good yield from the reaction of [HC(CMeNAr)2]K with MnI2 in THF. Treatment of 3 under reflux in toluene and removing all the volatiles in vacuo afforded the dimeric compound [{HC(CMeNAr)2}Mn]2(,-I)2 (4). Displacement of the coordinated THF in 3 by a strong Lewis base C[N(iPr)CMe]2 or by adding C[N(iPr)CMe]2 to the toluene solution of 4 readily gave the N-heterocyclic carbene adduct [{HC(CMeNAr)2}]MnI{C[N(iPr)CMe]2} (5). Reduction of 5 with sodium/potassium alloy at room temperature unexpectedly resulted in the formation of the monomeric compound [{HC(CMeNAr)2}]MnNHAr{C[N(iPr)CMe]2} (6). Alternatively 6 was obtained by the salt elimination reaction of 5 with LiNHAr. Compounds 5 and 6 are the first examples of divalent manganese N-heterocyclic carbene adducts and the first manganese non-carbonyl carbene complexes. The single crystal X-ray structural analyses reveal that compounds 3 and 6 are monomeric and compound 4 is dimeric in the solid state. The manganese centers in these compounds exhibit a distorted tetrahedral geometry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Synthesis of a Hexadentate Hexameric Aluminum Imide and Its Metathesis Reactions

    N. Dastagiri Reddy
    Abstract The reaction of AlH3·NMe3 with one equivalent of 2-cyanothiophene in toluene afforded [HAlNCH2(C4H3S)]6 (2) in good yield. Treatment of 2 with SiMe3Br and SiMe3Cl in toluene under refluxing conditions resulted in the formation of compounds [BrAlNCH2(C4H3S)]6 (3) and [ClAlNCH2(C4H3S)]6 (4), respectively. In a similar way [PhC,CAlNCH2(C4H3S)]6 (5) was readily obtained from the reaction between 2 and PhC,CH. When 2 was treated with PhSH the Al-N cluster core dissociated and a four-membered ring compound [(PhS)2AlNHCH2(C4H3S)]2 (6) was formed. In contrast, a similar hexameric aluminum imide (HAlNCH2Ph)6 (1) retains its Al-N network when treated with PhSH to yield (PhSAlNCH2Ph)6 (7). An exchange of ethyl groups and hydrides occurred when 2 was treated with excess of ZnEt2, forming [EtAlNCH2(C4H3S)]68. Compounds 2,4 and 6,8 were characterized by X-ray single-crystal analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Application of Selective Palladium-Mediated Functionalization of the Pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine Heterocyclic System for the Total Synthesis of Variolin B and Deoxyvariolin B,

    Alejandro Baeza
    Abstract The reaction of protected 3-bromo-2-(bromomethyl)-4-methoxypyrrolo[2,3- b]pyridine and tosylmethyl isocyanide (TosMIC) afforded a pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine derivative in good yield. This compound was transformed through installation of the pyrimidine moiety in the C5 position, hydrolysis, and decarboxylation in an advanced intermediate for the total or formal synthesis of the naturalalkaloid variolin B. Reaction of 3-bromo-2-(bromomethyl)-4-chloropyrrolo[2,3- b]pyridine with N -tosylmethyl dichloroformimide as a synthetic TosMIC equivalent afforded trihalo-substituted pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine. This compound was used in a new total synthesis of the alkaloid variolin B by selective and sequential C,N, C,C, and C,O palladium-mediated functionalization at the C9, C5, and C4 positions of the pyrido[3,,2,:4,5]pyrrolo[1,2- c]pyrimidine system. A formal synthesis of deoxyvariolin B is also described by using the same synthetic strategy. [source]

    Electro-Organocatalysis: Enantioselective ,-Alkylation of Aldehydes

    Xuan-Huong Ho
    Abstract The asymmetric organocatalyzed ,-alkylation of aldehydes via a cationic radical enamine intermediate was performed under environmentally benign electro-oxidation conditions without the use of chemical oxidants. To promote the desired ,-alkylation reaction of aldehydes, various aldehydes with xanthene or cycloheptatriene groups were exposed to electro-organocatalytic conditions to afford optically active ,-substituted aldehydes (,-alkylated aldehydes) in good yield. A reaction mechanism involving the cationic radical enamine was proposed based on the cyclic voltammetry (CV) results, DFT calculations, and control experiments. [source]

    Oxime Carbonates: Novel Reagents for the Introduction of Fmoc and Alloc Protecting Groups, Free of Side Reactions

    Sherine N. Khattab
    Abstract Fmoc and Alloc protecting groups represent a consistent alternative to classical Boc protection in peptide chemistry. The former was established in the last decades as the ,-amino protecting group of choice, whereas the latter allows a fully orthogonal protection strategy with Fmoc and Boc. Usually, the introduction of the Fmoc and Alloc moieties takes place through their halogenoformates, azides, or activated carbonates. This rather simple reaction is accompanied by several side reactions, specially the formation of Fmoc/Alloc dipeptides and even tripeptides. The present work describes new promising Fmoc/Alloc-oxime reagents, which are easy to prepare, stable, and highly reactive crystalline materials that afford almost contaminant-free Fmoc/Alloc-amino acids in high yields by following a conventional procedure. Amongst the Fmoc-oxime derivatives, the N -hydroxypicolinimidoyl cyanide derivative (N -{[(9H-fluoren-9-yl)methoxy]carbonyloxy}picolinimidoyl cyanide) gave the best results for the preparation of Fmoc-Gly-OH, which is the most predisposed to give side reactions. The same Alloc-oxime analogue afforded the preparation of Alloc-Gly-OH in good yield, purity, and extremely low dipeptide formation, as analyzed by reverse-phase HPLC and NMR spectroscopy. [source]

    Nd(OTf)3 -Catalyzed Cascade Reactions of Vinylidenecyclopropanes with Enynol: A New Method for the Construction of the 5,7,6 Tricyclic Framework and Its Scope and Limitations

    Liang-Feng Yao
    Abstract We report in this paper a Lewis acid [Nd(OTf)3]-catalyzed protocol to construct compounds containing a 5,7,6 tricyclic framework in good yield from readily accessible starting materials vinylidenecyclopropanes (VDCPs) 1 and enynols 2a,c under mild conditions. Upon examination of the scope and limitations of this reaction, it was found that the corresponding highly functionalized cyclopentane derivatives could be formed in good yields from the reaction VDCPs 1 and enol 2e or dienol 2c under identical conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]