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  • Carbene complexes  (6)
  • (2,3,4,6-Tetra-O-pivaloyl-β-D-galactopyranosylamine, carbene complexes of  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 259-264 
    ISSN: 0009-2940
    Keywords: (Cycloheptatrienylmethyl)carbene complexes ; 4,5-Homotropilidenes ; Cyclopropanation, intramolecular ; Carbene complexes ; Cope rearrangement, metal influence on ; Rhodium complexes ; Iron complexes ; Chromium complexes ; Tungsten complexes ; Calculations, AM1, MNDO, PM3 ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 57[1].  -  4,5-Homotropilidenes by Intramolecular Cyclopropanation of (Cycloheptatrienylmethyl)carbenechromium or -tungsten Complexes(Cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)-CH2C7H7 [3: LnM=Cr(CO)5 (a), W(CO)5 (b)] are obtained in yields of 80% by the reaction of the corresponding methylcarbene complexes LnM=C(OEt)CH3 1 with tropylium tetrafluoroborate (2) in THF/Et3N. Alkylation of 3 with 2 gives [bis(cycloheptatrienyl)methyl]carbene complexes LnM=C(OEt)CH(C7H7)2 [4: LnM=Cr(CO)5 (a), W(CO)5 (b)]. Thermolysis of 3 leads to the formation of an equilibrium mixture of the 4,5-homotropilidenes 5 and 6. According to NMR measurements and AM1 calculations the formation of 6 is strongly favored. An equilibrium between 4,5-homotropilidene complexes is significantly different from that of the metal-free ligands. By the reaction of 5/6 with bis(ethylene)rhodium 1,3-pentanedionate (8) the complexes 9 and 10 of both 4,5-homotropilidenes 5 and 6 are obtained in a 1:3 ratio. The (1,5-diene)rhodium(I) complexes 9 and 10 are nonfluxional and configurationally moderately stable at 20°C. The reaction of 5/6 with Fe2(CO)9 gives the π-allyl,σ complexes 11 and 12 in a 10:3 ratio, both of which may be derived from the minor 4,5-homotropilidene isomer 5. In 11 a vinylcyclopropane unit of 5 serves as a four-electron donor for a Fe(CO)3 group. In 12 the 4,5-homotropilidene unit is coordinated as a six-electron donor to a Fe2(CO)6 unit.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2325-2330 
    ISSN: 0009-2940
    Keywords: Pyrroles, 2-amino-3-ethoxy ; Ketenimines by metathesis of carbene complexes with isocyanides ; Carbene complexes ; Chromium, (aminovinyl)carbene complexes ; Tungsten, (aminovinyl)carbene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 66[1].  -  2-Aminopyrroles by Metathesis of (β-Aminovinyl)carbene Complexes of Chromium and Tungsten with Isocyanides(β-Aminovinyl)carbene complexes LnM=C(OEt) - CH=C(Ph)-NHR (Z)-3a - d [LnM = (CO)5Cr, (CO)5W; R = Ph, iPr, CH2Ph] react with two equivalents of isocyanides R1 - NC 5 (R = c-C6H11, t-C4H9) to give 2-amino-3-ethoxypyrroles 7a - e and isocyanide complexes LnM(R1 - NC) 6. The reaction involves the formation of ketenimine complexes by metathesis. These are key intermediates. The pyrroles 7 are easily oxidized by air to give amidines PhN(R1NH)C - C(OEt)=CH - COPh 9 (R = c-C6H11, t-C4H9). 7a forms a Michael adduct 10a as well as a Diels-Alder adduct 11a with N-phenylmaleimide. A 1-amino-2-ethoxybenzene 12a is obtained from 11a by elimination of aniline.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0009-2940
    Keywords: [2-(Amino)ethenyl]carbene complexes ; 3-Amino-1,2-propadienylidene complexes ; (2,3,4,6-Tetra-O-pivaloyl-β-D-galactopyranosylamine, carbene complexes of ; Ketene imines ; Isocyanides ; Pyrroles ; Alkynylcarbene complexes of chromium and tungsten ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 70[1].  -  [2-(Galactopyranosylamino)ethenyl]carbene and 3-(Galactopyranosylamino)-1,2-propadienylidene Complexes on 3-Addition of 2,3,4,6-Tetra-O-pivaloyl-β-D-galactopyranosylamine to Alkynylcarbene Complexes (M = Cr, W).  -  Atropisomeric Galactopyranosyl Pyrroles by Reaction of [2-(Galactopyranosyl-amino)ethenyl]carbene Complexes with IsocyanidesEnantiomeric pure (2-aminoethenyl)carbene complexes LnM=C(OEt)—CH=C(Ph)NHR* (Z)-3 and 3-amino-1,2-propadienylidene complexes LnM=C=C=C(Ph)NHR* 4 [R* = 2,3,4,6-tetra-O-pivaloyl-β-D-galactopyranosyl] are obtained by the addition of galactopyranosylamine R*-NH2 2 to the corresponding alkynylcarbene complexes LnM=C(OEt)—C≡CPh 1 [LnM = (CO)5Cr, (CO)5W]. Treatment of (Z)-3 with two equivalents of tert-butyl isocyanide (5) affords isocyanide complexes 6 and ketene imines 7. The latter cyclize spontaneously to give galactopyranosylpyrroles 8 which form stable atropisomers 8A and 8B.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-193X
    Keywords: Carbene complexes ; Enamines ; Metallatrienes ; Cyclopentadienes ; Dihydropyrroles ; spiro-Tetrahydropyrroles ; Iminium carbonylmetalates ; Dimetallapolyenes ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reactions of the [(1-alkynyl)carbene]tungsten complex (CO)5W=C(OEt)C≡CPh (1) with 1-aminocyclohexenes 2a-c and 7a-c afford different types of products depending on the amino substituents and the reaction conditions. (4-Aminocyclobutenyl)carbene complexes B have been shown to be generated in the first reaction step through a [2+2] cycloaddition. These are key intermediates and afford cross-conjugated tungstatrienes E, (conjugated) 1-tungsta-1,3,5-hexatrienes G, or (non-conjugated) 1-tungsta-1,3,6-heptatrienes F by following competing reaction pathways. Cross-conjugated 1-tungstatrienes 3 have been isolated in 52-74% yield by performing the reactions of 1-aminobenzocyclohexenes 2a-c with compound 1 in pentane. In dichloromethane instead of pentane, (conjugated) 1-tungsta-1,3,5-hexatrienes 4 are obtained, which subse-quently undergo fragmentation to give cyclopentadienes 6 (by π-cyclization) and dihydropyrroles (by α-cyclization) in a molar ratio dependent on the nature of the amino substituents. (Non-conjugated) 1-tungsta-1,3,6-heptatrienes 10 are generated upon reaction of 1-aminocyclohexenes 7a-c with compounds 1, which are transformed into cyclopentadienes 12 via conjugated 1-tungsta-1,3,5-hexatrienes 9 as intermediates. Reactions of 1-tungsta-1,3,6-heptatrienes 10 with the (1-alkynyl)carbene complex 1 afford dinuclear compounds 14, which subsequently yield indenes 15 (by two successive π-cyclization steps) and spiro-tetrahydropyrroles 16 (by both a π-cyclization and an α-cyclization step), depending on the steric bulk of the amino substituent.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 17-31 
    ISSN: 1434-193X
    Keywords: Carbene complexes ; Chromium ; Tungsten ; Hexatrienes ; Azahexatrienes ; Transmetalation ; Alkynes ; Polyenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The term 1-metalla-1,3,5-hexatriene applies to a huge number of transition metal carbene complexes which contain a 1,3-butadien-1-yl side chain attached to the carbene carbon atom. Compounds of this type were found to play a crucial role as key intermediates and have also been utilized as stoichiometric reagents in a number of high-yielding transformations, which may successfully be applied to organic syntheses. Typical reaction pathways, structural features, and preparations of such compounds (with focus on M = Cr and W) have been summarized.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-193X
    Keywords: Carbene complexes ; 1-Metallahexatrienes ; Cyclopentadienes ; Carbene complexes ; Tungsten ; Domino cyclization ; Pentalenes ; Spirocyclopentanes ; Spiro compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -1,3-Dioxytetrahydropentalenes 9 have been generated by base-catalyzed addition of protic oxygen nucleophiles ROH 6a-g (RO = carboxy or phenyloxy) to the [2-(1-cyclopentenyl)ethynyl]carbene tungsten complex 3. Compounds 9 are highly reactive and afford (cyclobutenyl)carbene complexes 12a-g through spontaneous [2+2] cycloaddition to a second molecule of the (1-alkynyl)carbene complex 3. Thermolysis of compounds 12 was found to generate indeno[b]-spiro-tricyclo[5.3.0.0]decadienes 18 through π-cyclization of the 1-tungsta-1,3,5-hexatriene unit involving insertion of carbon monoxide into the W—C bond.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1434-193X
    Keywords: Carbene complexes ; Catalysis ; Metallahexatrienes ; Vinyl cyclopentadienes ; Transmetallation ; Rhodium ; Tungsten ; Chromium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report on the first example of a transition metal-catalyzed cyclization reaction of a Fischer carbene complex. It comprises the generation of vinyl- and divinyl cyclopentadienes under exceedingly mild conditions at 20 °C by condensation of (1-amino-1,3-butadien-2-yl)carbene complexes (= cross-conjugated metallahexatrienes) (CO)5M=C(OEt)C(=CHNR2)CR1=CHR23 (M = Cr, W) with alkynes R3C≡CH 4 (R3 = Ph, cyclohex-1-enyl, isopropenyl, methoxymethyl, 1-trimethylsiloxycyclohex-1-yl) in the presence of catalytic amounts of [(COD)RhCl]2. The starting compounds 3 are accessible in high yields by addition of enamines (E)-R2NCH=CHR22 to (1-alkynyl)carbene complexes (CO)5M=C(OEt)C≡CR11 (M = Cr, W; R1 = Ph, cyclohex-1-enyl).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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