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  • Palladium  (34)
  • Wiley-Blackwell  (34)
  • American Institute of Physics (AIP)
  • Copernicus
  • 2010-2014
  • 1995-1999  (34)
  • 1999  (34)
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  • Wiley-Blackwell  (34)
  • American Institute of Physics (AIP)
  • Copernicus
  • Springer  (2)
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  • 2010-2014
  • 1995-1999  (34)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 129-134 
    ISSN: 1434-193X
    Keywords: Tetrahydro-2-vinylquinoxaline ; Cyclization ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Reaction of (Z)-1,2-bis(methoxycarbonyloxy)but-2-ene (2) with various N,N-bis(arylsulfonyl)-o-phenylenediamines 1 was catalyzed by a palladium complex associated with chiral ligands to give optically active 1,4-bis(arylsulfonyl)-1,2,3,4-tetrahydro-2-vinylquinoxalines 3 with up to 62% ee. The use of (S)-MeOBIPHEP as the chiral ligand and N,N-bis(p-tolylsulfonyl)-o-phenylenediamine (1i) as the nucleophile led to the highest ee at 25 °C, regardless of the solvent used. The enantioselectivity of the cyclization is strongly affected by the nature of the substituents at the nitrogen atom.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
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  • 3
    ISSN: 1434-193X
    Keywords: 1β-Methylcarbapenems ; Palladium ; Ruthenium ; Catalysis ; Cyclizations ; Stereoselective hydrogenation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -An efficient diastereoselective multi-step synthesis of bicyclic 1β-methylcarbapenem antibiotic precursors has been developed, starting from the commercially available 4-acetoxyazetidin-2-one 4. Chiral ruthenium catalysts are used in the hydrogenation step to control the β-stereochemistry at the 1-position, and a π-allylpalladium ring-closure strategy is used to form the functionalized carbapenem skeleton.
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  • 4
    ISSN: 1434-193X
    Keywords: Cyclocarbonylation ; Alkynes ; Catalysis ; Palladium ; Vinyl triflates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -o-Ethynylphenols react with vinyl triflates, in the presence of tetrakis(triphenylphosphane)palladium(0) and under carbon monoxide, to form 3-alkylidene-2-coumaranones in good yield.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1075-1084 
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Atropisomerism ; Bis(hydroxylation) ; Conformational analysis ; Palladium ; Vitamin E ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Several new approaches for the enantioselective synthesis of the chromane moiety of vitamin E are described. Sonogashira coupling of 3a with the alkyne 4 and subsequent elimination gave 6, which was bis(hydroxylated) in 93% yield and with 85% ee. Recrystallization gave enantiopure 7a, which was hydrogenated and transformed into the vitamin E precursor 11. The bis(hydroxylation) of 18 and 21 to give 9 and 22, respectively, was less than satisfactory, proceeding with ee values of 28% and 18%. In contrast, stereoselective allylation of ketone 15 followed by removal of the protecting group or ozonolysis of the allyl moiety furnished the allyl alcohol 26 and the aldehyde 27, respectively, in almost enantiopure form, which again could be used as precursors for vitamin E. Partial hydrogenation of 5a gave the alkene 32a and that of 28 the alkene 30b, both of which show interesting atropisomerism.
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  • 6
    ISSN: 1434-193X
    Keywords: Aporphines ; Nitrogen heterocycles ; Palladium ; Homogeneous catalysis ; Dibenzo[de,g]quinolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dibenzo[de,g]quinolines 5were formed by the palladium-catalysed heteroannulation of disubstituted alkynes and 1-iodo-10-(dimethylamino)phenanthrene (3c). Symmetric alkynes led to high levels of regioselectivity. These reactions constitute a new synthesis of the B-ring system of aporphine heterocycles.
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  • 7
    ISSN: 1434-193X
    Keywords: Homogenous catalysis ; Palladium ; Cross-coupling ; Heterocycles ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-acceptor-substituted 2,3-dibromofurans 1 and 2 underwent a regioselective Pd0-catalyzed coupling reaction at the C-2 carbon atom. With alkynes the corresponding 2-alkynylfurans 4 and 5 were accessible (49-97% yield). Alkyl-, aryl-, and alkenylzinc reagents gave the 2-substituted furans 8 starting from compound 2 (66-84% yield). The 2-allylfurans 8e and 8f were obtained by a regioselective Stille coupling in 79% and 73% yield. The latter reaction was also applied to the parent 2,3-dibromofuran (27) and yielded the substitution product 28 (60% yield). Subsequent Pd0-catalyzed reactions to introduce a methyl group in 3-position by a methyldebromination were successfully conducted for 2-alkynyl-3-bromofurans with MeZnCl and PdCl2(PPh3)2 as the catalyst in THF (reflux) to yield compounds 13-16 and 24 (67-76%) and with SnMe4 and PdCl2[P(o-Tol)3]2 as the catalyst in DMA (90 °C) for the 2-allyl-3-bromofuran 8e to yield 18 (70%). The more facile reaction of the 2-alkynylfurans relative to those of furans bearing an sp3-carbon atom at C-2 appears to be due to steric reasons. Studies on the 2-alkyl-3-bromofuran 20 supported this notion. With the regioselective coupling methodology the terpene rosefuran (22) was prepared in four steps starting from furan 2 (35% yield overall). The F5 furan fatty acid (26) was synthesized from furan 1 in five steps (29% yield overall).
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2665-2673 
    ISSN: 1434-193X
    Keywords: 2-Vinyl-2,3-dihydro-benzo[1,4]dioxins ; Cyclizations ; Palladium ; Chirality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1,4-bis(methoxycarbonyloxy)but-2-ene (2a-3a) or 3,4-bis(methoxycarbonyloxy)but-1-ene (4a) with various substituted benzene-1,2-diols was catalyzed by a palladium(0) complex to give substituted 2-vinyl-2,3-dihydro-benzo[1,4]dioxins in good yields via a tandem allylic substitution reaction. In the case of 4-substituted benzene-1,2-diols, the ratio of regioisomers is determined by the relative acidity of the two phenolic protons. For 3-substituted benzene-1,2-diols, this ratio is determined only by steric effects in the case of alkyl substituents, although it is determined mainly by the relative stabilities of the corresponding phenates for other substituents; however, for 3-nitrobenzene-1,2-diol, this ratio is determined by the relative leaving-group ability of 2-nitro- or 3-nitrophenate. When the cyclisation was performed in the presence of an optically active phosphane, chiral 2-vinyl-2,3-dihydro-benzo[1,4]dioxin (5) was obtained with enantioselectivity of up to 45% using BINAP as the chiral phosphane.
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  • 9
    ISSN: 1434-1948
    Keywords: 2-Acetylpyridine 4-methylthiosemicarbazone ; Palladium ; Platinum ; Group-12 metal(II) complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 2-acetylpyridine 4-methylthiosemicarbazone (H4ML) with halides of zinc(II), cadmium(II), and mercury(II) afforded complexes of the form [M(H4ML)X2] [M = ZnII (1-3), CdII (4-6) or HgII (7-9); × = Cl, Br, or I]. Reaction of H4ML with K2PdCl4 and K2PtCl4 gave compounds of the form [M(4ML)Cl] [M = PdII (10) or PtII (11)]. In all the new compounds, which were characterized by elemental analyses, conductance measurements, and electronic, IR and 1H- and 13C-NMR spectroscopy, and by 113Cd-, 195Pt-, or 199Hg-NMR spectroscopy when relevant, the ligand is N,N,S-tridentate, coordinating to the metal centre through its pyridine and azomethine nitrogen atoms and its thiocarbonyl sulfur atom, as was confirmed by X-ray diffraction studies in the cases of 4· 2 DMSO, 5· 2 DMSO, 6· 2 DMSO, 7· 2 DMSO, 10, and 11. In in-vitro assays, only [Zn(H4ML)Cl2] and [Zn(H4ML)Br2] showed some sign of antifungal activity against Aspergillus niger or Paecilomyces variotii.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/98381_s.pdf or from the author.
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  • 10
    ISSN: 1434-1948
    Keywords: Palladium ; N ligand ; P ligand ; Copolymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new classes of organometallic palladium(II) compounds, namely [Pd(N-N)(CH2NO2)2] and [Pd(L-L)(N-N)(CH2NO2)][PF6] [N-N = 2,2′-bipyridine, 1,10-phenanthroline and their substituted derivatives; L-L = 1,3-bis(diphenylphosphino)propane or N-N] have been synthesized and fully characterized both in the solid state and in solution. The crystal structures of [Pd(phen)2(CH2NO2)][PF6] and of [Pd(dppp)(tmphen)(CH2NO2)][PF6] show a square-planar coordination geometry for the palladium atom and an unexpected monodentate coordination for the N-N ligand. The behavior in solution, investigated by NMR spectroscopy, shows the presence of dynamic processes involving only the N-N molecules. This fluxional behavior is different for [Pd(N-N)2(CH2NO2)][PF6] and [Pd(dppp)(N-N)(CH2NO2)][PF6]: in the former it most likely involves the substitution of the nitrogen atom trans to the CH2NO2 moiety by the uncoordinated nitrogen atom of the other N-N ligand; in the latter it may involve the exchange of the two nitrogen atoms at the same coordination site (flipping).
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1073-1076 
    ISSN: 1434-1948
    Keywords: C-C coupling ; Homogeneous catalysis ; Kinetics ; Palladium ; Phosphorus amidite ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complex 1bshows an unprecedented high activity in the Heck reaction. Kinetic studies show that in this system not the oxidative addition but the alkene coordination/migratory insertion is the rate determining step.
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  • 12
    ISSN: 1434-1948
    Keywords: Palladium ; Phosphane ligands ; Bite angle ; Allylic alkylation ; Molecular modelling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The natural bite angle of bidentate phosphane ligands influences the isomer distribution (syn and anti) in (1-methylallyl)(bisphosphane)Pd OTf complexes. It was found (31P- and 1H-NMR studies) that the syn/anti ratio changes from 12 (dppp) to 1.3 (sixantphos). Molecular orbital calculations [PM3(tm) level] indicate that for ligands inducing a large bite angle, the phenyl rings of the ligand embrace the allyl moiety, thus influencing the syn/anti ratio. This bite-angle effect on the syn/anti ratio is transferred to the regioselectivity in stoichiometric allylic alkylation. Ligands inducing large bite angles direct the regioselectivity towards the formation of the branched product 2. Catalytic alkylation of (E)-2-butenyl acetate showed that for ligands with a small bite angle the regioselectivity of the catalytic and stoichiometric alkylation are in good agreement. This correspondence is worse for ligands with a larger bite angle, which is rationalised in terms of the relative rates of syn/anti isomerisation and alkylation. The ligand with the largest bite angle (sixantphos) gives the most active catalytic species.
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  • 13
    ISSN: 1434-1948
    Keywords: Palladium ; Bidentate nitrogen ligands ; Carbohydrates ; Alkenes ; Enantioselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral N,N-chelates of formula 6-Me-pyridine-2-CH=N-R (1) and R-N=CH-CH=N-R (2) (R = 6-deoxy-α-D-glucoside or 6-deoxy-α-D-mannoside residue) and their palladium(0) complexes [Pd(N,N-chelate)(olefin)] (I) were prepared. Symmetrical type 2 ligands induced higher enantioselectivity in the coordination of prochiral olefins. The ability of a type 1 chelate to promote a stereoselective process was also assessed, i.e. dimethylfumarate inserted into the Pd-Me bond formed upon methylation of a type I complex with 50% ee. Finally, a water-soluble Pd0 complex was also prepared by deprotecting the alcoholic functions on the sugar residue, and its molecular structure determined through X-ray diffractometry.
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  • 14
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1081-1085 
    ISSN: 1434-1948
    Keywords: Palladium ; Anionic complexes ; Phosphane substitution ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Halide ions react with PdX2(PPh3)2 (X = Cl, Br, I) complexes in an equilibrated reaction in which the phosphane ligand is substituted by the halide X- to form anionic complexes PdX3(PPh3)- in THF and DMF. The equilibrium constants have been determined by cyclic voltammetry.
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  • 15
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 471-482 
    ISSN: 1434-1948
    Keywords: Quinine ; Cinchonine ; Palladium ; Platinum ; Silver ; Gold ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of metal complexes in which quinine (L1) and cinchonine (L2) are coordinated via the four possible donor atoms was prepared and characterized. Coordination of the tertiary N atom of quinine is observed in [L1MPPh3]+NO3- [M = Au (1), Ag (2)], [L1Pd(COD)(Cl)]+ NO3- (3) and L1Pd(Cl)(allyl) (4). The mono anion of quinine functions as N,O chelate ligand in (L1-H+)M(Cl)(PR3) (M = Pd, Pt, 5-10), [(L1-H+)Pd(en)]+NO3- (11) and (L1-H+)2TiCl2 (12). Protection of the tertiary N atom of quinine by methylation or protonation allows the synthesis of the quinoline complexes [(L1CH3+)M(Cl)2(PR3)]+ BF4- (M = Pd, Pt, 14-18), [(L1CH3+)Ir(Cl)2(Cp*)]+ BF4- (19), [(L1+H+)M(Cl)2(PR3)]+ CF3SO3- (M = Pd, Pt, 20-22) and (L2+H+)(ZnCl3-) (23). Quinine and cinchonine act as N,O-N bridge in the complexes (R3P)(Cl)M(μ-L1-H+)M(Cl)2(PR3) (M = Pd, Pt, 24, 25, 27, 28), (Cp*)(Cl)Ir(μ-L1-H1)Ir(Cl)2(Cp*) (29), (EtP3)(Cl)Pd(μ-L2-H+)Pd(Cl)2(PEt3) (26), and as N-N bridge in the complexes [(Ph3P)Au(μ-L1)Au(PPh3)]+NO3- (30) and (allyl)(Cl)Pd(μ-L1)Pd(Cl)(allyl) (31). Coordination of quinine via the C=C double bond occurs in [(L1+2 H+)PtCl3]+Cl- (32). The structures of 11, 13, 19, 23, 26 and 32 were determined by X-ray diffraction. In most cases the coordination mode and the conformation of quinine can also be derived from the 1H-NMR spectra.
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  • 16
    ISSN: 1434-1948
    Keywords: Palladium ; Azide ; Pyridine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Palladium(II) azide (1) was synthesized by reaction of palladium nitrate and sodium azide. 1 was characterized by AAS, IR, and 14N-NMR spectroscopy. Bis(azido)bis(pyridine)palladium(II) (2) and tetramminepalladium tetraazidopalladate(II) (3) were synthesized by a high-yield reaction. Both were characterized by X-ray structural analysis, IR, Raman, and NMR spectroscopy.
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  • 17
    ISSN: 1434-1948
    Keywords: Palladium ; Carbenes ; Metallacycles ; 1,2,4-Triazole ; Coordination modes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mononuclear palladium carbene complexes 2a-c and 3 derived from 1,1′-methylenebis(4-alkyl-4,5-dihydro-1H-1,2,4-triazole-5-ylidene) have been obtained by the reaction of 1,1′-methylenebis(4-alkyl-1,2,4-triazolium) diiodides 1a-d with palladium acetate under mild conditions. The mononuclear complexes 2a-c have been transformed into their corresponding trans-binuclear complexes 4a-c. All compounds were characterized by spectroscopic techniques and the dynamic behavior of 2a-cand 4a-c has been studied. The X-ray structures of 2a and 4c are reported.
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  • 18
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 959-964 
    ISSN: 1434-1948
    Keywords: Nickel ; Palladium ; Cobalt ; N ligands ; Crystal structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of new palladium(II) (1), nickel(II) (2a and 2b), and cobalt(II) (3) complexes bearing the unsymmetrical, bidentate nitrogen ligand 2,6-bis(1-methylethyl)-N-(2-pyridinylmethylene)phenylamine (L) is described. The solid-state structures of 1, 2a, and 2b have been determined by single-crystal X-ray diffraction. The PdII compound exists in the monomeric form whereas the nickel complexes were observed as centrosymmetric dimers with slightly distorted square-pyramidal coordination sphere around each nickel center.
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  • 19
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    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1325-1333 
    ISSN: 1434-1948
    Keywords: Platinum ; Palladium ; Platinum blues ; Naphthyridine complexes ; Trinuclear complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All three dinuclear complexes [Pd2(donp)2(bpy)2] (1) (H2donp = 1,8-naphthyridin-2,7-dione), [Pd2(H2nonp)2(bpy)2](ClO4)2 (2), and [Pt2(H2nonp)2(bpy)2](PF6)2 (3) (H3nonp = 7-amino-1,8-naphthyridin-2-one) exhibit the μ-1ĸN1:2ĸN8 bridging mode for their head/tail orientated naphthyridine ligands. Whereas 1 and 3 may be prepared by direct reaction of the dinucleating ligand with [MCl2(bpy)], formation of competing tripalladium(II) complexes must be avoided for 2 by employment of the precursor H2acnonp (7-acetamido-1,8-naphthyridin-2-one), which affords [H2nonp]- on cleavage of its original acetyl group. A mixture of the head/tail (4a) and head/head (4b) isomers of [Pd3(Hnonp)2(bpy)3](ClO4)2 is obtained when H3nonp is treated with [PdCl2(bpy)] and LiOH at room temperature for 2 d, followed by precipitation with LiClO4. Contrastingly exclusive formation of 4a is observed upon refluxing this reaction mixture for 3 d in aqueous solution. The [Hnonp]2- ligands exhibit a μ3-1ĸN1:2ĸN8:3ĸN7 bridging mode that leads to short Pd···Pd interactions of 2.781(2) and 2.775(2) Å. Similar metal-metal distances of 2.771(3) and 2.816(3) Å are observed in head/head-[Pt3(acnonp)(Hnonp)(bpy)3]Cl2 (5). An in situ 2e--oxidation (Ag+/Ag) of the [Pt3]6+ core in triplatinum(II) species such as 5 formed by the reaction of [PtCl2(bpy)] with H2acnonp allows the isolation of diamagnetic dark-brown head/head-[Pt3(Hnonp)2(NO3)(bpy)3](ClO4)2(NO3) (6) with an average oxidation state of Pt (2.67+). The Pt-Pt distances of 2.723(2) and 2.670(2) Å are markedly shorter than in 5.
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  • 20
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3085-3087 
    ISSN: 1434-193X
    Keywords: Nucleoside analogue ; Nucleosides ; Palladium ; Dihydroxylations ; Catalysts ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convenient diastereoselective synthesis of an immediate precursor for a rapid access to a variety of homo-carbocyclic nucleosides, is described. The synthetic scheme involves a high yielding new type of Pd(0) catalyzed cyclization of a suitable hydrazine derivative together with a stereospecific OsO4 triggered dihydroxylation step.
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  • 21
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Heterocycles ; Palladium ; Alkylations ; Allyl complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A convenient synthesis of racemic tetrahydropyridine 1 was developed. Pd-catalyzed allylic alkylation of 1 with malonate and dimethylacetoxymalonate as nucleophiles with the phosphanylcarboxylic acid L1 and the dihydrooxazol L2 as ligands, were carried out and gave enantiomeric excesses of up to 98%. Absolute configurations were determined for all compounds described. From the alkylation products (+)- and (-)-2a, and (+)- and (-)-2b a variety of versatile, nonracemic chiral intermediates were prepared.
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  • 22
    ISSN: 1434-193X
    Keywords: Alkaloids ; Asymmetric synthesis ; Palladium ; Amino alcohols ; Natural products ; Monomorine I ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile method for the preparation of indolizidine alkaloids from 1-benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols as stereodefined key intermediates has been developed. The utility of this approach was demonstrated by the synthesis of (+)-monomorine I.
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  • 23
    ISSN: 1434-193X
    Keywords: Palladium ; Hydrovinylation ; Cyclizations ; Furan-2(5H)-ones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of alkynes with vinyl triflates in the presence of catalytic amounts of Pd(OAc)2 and HCOOK, omitting phosphane ligands, affords hydrovinylation products usually in good to high yields. The reaction has been employed to develop a regioselective synthesis of 3-vinylfuran-2(5H)-ones from methyl 4-hydroxy-2-butynoates.
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  • 24
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1029-1039 
    ISSN: 1434-1948
    Keywords: Palladium ; Primary benzylamines ; NMR spectroscopy ; Structure elucidation ; Conformation analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ortho-Palladation of a sterically crowded primary benzylamine, α-phenylneopentylamine, was accomplished in a moderate yield of 50% in the reaction with the weakest of palladation agents (Li2PdCl4) under very mild conditions, due to a steric promotion of an aromatic C-H bond activation. The structure of dimer 1a thus formed and the palladacycle conformation were established on the basis of 1H-NMR spectroscopy of its mononuclear derivatives with [D5]pyridine (3a) and triphenylphosphane (4a), and an X-ray investi-gation of the latter.Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2005/1999/98367_s.pdf or from the author.
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  • 25
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1875-1883 
    ISSN: 1434-193X
    Keywords: Arenediazonium salts ; Potassium organotrifluoroborates ; Cross-coupling ; Palladium ; Biaryls ; Styrenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of various potassium organotrifluoroborates bearing either aryl, alkenyl, or alkynyl substituents is described. These stable salts are shown to be very efficient partners in palladium-catalysed cross-coupling reactions with arenediazonium salts, affording biaryl and styrene derivatives in high yields.
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  • 26
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2231-2234 
    ISSN: 1434-193X
    Keywords: Palladium ; Allyl complexes ; Phenolic nucleophiles ; Chromene ; C-C couplings ; Flavonoids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of 2-phenyl-2H-chromene (3-flavene) and cinnamaldehyde aryloxy-hemiacetal, involving nucleophilic substitution by phenols of the π-allyl palladium complex formed from the acylal of cinnamaldehyde in the presence of catalytic amounts of palladium(0) (10 mol-%), are presented. Alternatively, the corresponding alcohol acetates furnish 1,3-diarylpropenes and cinnamyl aryl ethers. Our results demonstrate the potent C-nucleophilicity of phloroglucinol in Tsuji-Trost reactions in flavonoid synthesis, and again illustrate the already well established O-nucleophilicity of phenols.
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  • 27
    ISSN: 1434-193X
    Keywords: Heterocycles ; Thiazoles ; Pyrido[3,4-c]thiazoles ; Triflates ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The readily available 2-substituted 5-acetyl-4-thiazolyl triflates 2are useful building blocks for the preparation of functionalised thiazoles by means of palladium-catalysed cross-coupling reactions with organometallic reagents and alkoxycarbonylation and deoxygenation reactions. The combination of palladium-catalysed coupling of 2 together with 1-alkynes/6-endo-dig annulation reactions in the presence of ammonia leads to functionalised pyrido[3,4-c]thiazoles in satisfactory yields. The utilisation of uncatalysed displacement reactions of the triflate group represents a very simple method for the synthesis of 4-N-,4-O-, and 4-S-substituted thiazoles.
    Additional Material: 2 Tab.
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  • 28
    ISSN: 1434-193X
    Keywords: Ambruticin ; Asymmetric synthesis ; Pyranose ; Carbohydrates ; C-Glycosylation ; Alkylations ; Palladium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new methodology has been applied to synthesize an isomer of the west part of (+)-ambruticin based on an efficient asymmetric de novo access to the A unit and sequential stereospecific reactions catalyzed by Pd0 for the construction of the B unit.
    Additional Material: 1 Ill.
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  • 29
    ISSN: 1434-193X
    Keywords: Alkylidenecyclopropanes ; Palladium ; Intramolecular 1,3-dipolar cycloaddition ; Thermal rearrangement ; Pyrrolo[3,4-b]pyridine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several alkylidenecyclopropanes have been synthesized in high yields and optical purity by palladium(0)-catalyzed substitution of 1-tosyloxy-1-vinyl cyclopropane using N-tosylamino esters or glycolic ester as nucleophiles. The new alkylidenecyclopropanes were transformed to the corresponding nitrones without loss of optical purity, except in the case of the phenylglycine derivative. The alkylidenecyclopropane nitrones underwent smooth in situ intramolecular cycloaddition with a stereoselectivity that was moderate with most substituted substrates, but complete with phenylglycine and proline derivatives. The spirocyclopropane isoxazolidines were transformed by selective thermal rearrangements in octahydro-2H-pyrrolo[3,4-b]pyridin-7-ones and octahydrofuro[3,4-b]pyridin-7-one, uncommon ring systems resembling biologically active natural and nonnatural products. An example of the extension of the process to an alkylidenecyclopropane nitrile oxide is also reported.
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  • 30
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2683-2688 
    ISSN: 1434-193X
    Keywords: Flavone ; Palladium ; Cross coupling ; Triflate ; Aminations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Palladium-catalyzed cross-coupling reactions of flavone triflates 2a-c, 4a with tetravinyltin give the corresponding vinylflavones 5a-d, whereas reactions with benzophenone imine, followed by cleavage, afford the corresponding aminoflavone.
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  • 31
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1333-1344 
    ISSN: 1434-193X
    Keywords: Cross-coupling ; Isomerizations ; Cycloisomerization ; Palladium ; Homogeneous catalysis ; Bicyclic vinylcyclopropanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Palladium-catalyzed cyclizations of the 2-bromo-1,6-diene 6 with an acetoxymethyl substituent on the bromoalkenyl moiety did not only lead to the expected 1-acetoxymethyl-1,3-diene 40 but also to the bicyclic vinylcyclopropane 35, the 1,3-diene 36 and the triene 37 (a dendralene). All these compounds result from an initial 5-exo-trig cyclization of the 2-bromo-1,6-diene. By proper choice of the reaction conditions (ligand, base, allylic leaving group) each of these compounds could be formed selectively. Small amounts (3-5%) of the isomerized 1-acetoxymethyl-1,3-diene 38 and the 6-endo product 39 were also isolated. With the acetoxymethyl substituent on the alkenyl moiety (compound 27) only the 1,4-diene 44 was formed. The related 1,6-enyne 57 with a methoxycarbonyloxymethylene substituent on the triple bond gave in 36% yield the 2,3-bis(bicyclo[3.1.0]hex-1-yl)-substituted 1,3-butadiene 63, which can be regarded as a dehydrodimer of the vinylcyclopropane 35. The presumption that the formation of 63 involves the alkenylpalladium species 65 was supported by its successful inter- as well as intramolecular trapping with formate as a hydride source to yield the vinylcyclopropane 35. The reaction pathways leading to the vinylcyclopropane derivatives 35 and 63 have in common that an alkylpalladium species rather undergoes a 3-exo-trig cyclization than an internal rotation followed by a β-hydride elimination.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98406_s.pdf or from the author.
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  • 32
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1421-1426 
    ISSN: 1434-193X
    Keywords: Anhydrides ; Coupling reaction ; Enols ; Palladium ; Tin ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -A new three-step synthesis of diarylmaleic anhydrides 6, starting from 3-aryl-2-hydroxybut-2-enedioates 2, is reported.
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  • 33
    ISSN: 1434-193X
    Keywords: Palladium ; Homogeneous catalysis ; Carbon monoxide ; Aromatic aldehyde ; Formic acid ; Carbonylation ; Electrochemistry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The palladium-catalyzed electrocarbonylation of aryl halides performed in the presence of formic acid under one atmosphere of carbon monoxide affords aromatic aldehydes in good to high yields.
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  • 34
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2327-2335 
    ISSN: 1434-193X
    Keywords: Quaternary carbon atoms ; Palladium ; Homogeneous catalysis ; Configuration determination ; NOE ; Taft parameter ; Diastereoselectivity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,2-asymmetric induction in the formation of new quaternary centers by palladium-catalyzed allylation of substituted cyanoacetates 1a-c was controlled by using 2,9-disubstituted 1,10-phenanthrolines as ligands, giving the allylated products 3a-c with like/unlike diastereoselectivities up to 94:6. The increased selectivities were caused by a tight wrapping of the allyl unit in the intermediate complexes. Differences in stereoselectivity for varying substrates can be understood when modified Taft parameters, the homo-Es values, are considered. The like/unlike isomers were assigned by using a combination of molecular modeling, NOE measurements and analyses of chemical shifts. An X-ray analysis of the acid 14 confirmed the structural assignment.
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