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  • 1
    Electronic Resource
    Electronic Resource
    Organische Synthesen mit Übergangsmetallkomplexen, 53 4-Methylencyclopentene und 5-Methylencyclohexenone aus „Fischer-Carben“- Chromkomplexen, Allenen und Alkine (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2335-2342 
    Details
    ISSN: 0009-2940
    Keywords: Cyclopentenes, 4-methylene-, synthesis of ; Cyclohexenones, 5-methylene-, synthesis of ; Tri(methylene)-methane chromium complexes ; [3 + 2]Cycloadditions with tri(methylene)methane complexes ; Carbene chromium complexes for organic synthesis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 53.  -  4-Methylenecyclopentenes and 5-Methylenecyclohexenones from “Fischer Carbene” Chromium Complexes, Allenes, and AlkynesA method is described for the two-step construction of 4-methylenecyclopentenes 6 and 5-methylenecyclohexenones 7 from Fischer carbene chromium complexes, allenes, and alkynes. In the first step a tri(methylene)methane complex 3 is generated by the addition of the carbene chromium complex (CO)5Cr = C(0Et)Ph (1) to the allene 2. The second step involves an addition of 3 to alkynes HC≡CR [5: R = Ph (a), SiMe3 (b)] at 75°C to give 6 and/or 7 in high chemical yields. The product ratios strongly depend on the substituents R.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241029
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  • 2
    Electronic Resource
    Electronic Resource
    Organische Synthesen mit übergangsmetall-Komplexen, 52 N-Vinylaminocarben- und N-(2-Propenyl)aminocarben-Komplexe durch Addition von Keteniminen an Carben-Eisenkomplexe (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1795-1803 
    Details
    ISSN: 0009-2940
    Keywords: Aminocarbene complexes of iron ; N-Vinylaminocarbene complexes ; π-Allyl,σ-complexes of iron ; N-(2-Propenyl)aminocarbene complexes ; Methylenation of ketene imines by carbene complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses with Transition Metal Complexes, 52 1). - N-Vinylaminocarbene and N-(2-Propenyl)aminocarbene Complexes by Addition of Ketene Imines to Carbene Iron ComplexesKetene imines R(Me)C = C = NPh (2, R = Me, Et, i-Pr) form 1 : 1 adducts with the carbene iron complex (CO)4,Fe=C(OEt)Ph (1). The initial step of the reaction involves an attack of the nitrogen atom of 2 at the carbene carbon atom of 1 and a subsequent rearrangement to give N-vinylaminocarbene complexes (E/Z)-4. In a parallel process with different regiochemistry the central carbon of the CCN unit is attached to the carbene carbon to yield π-allyl,σ-complexes (E/Z)-3. Alkylation of 3a with [Et3O]BF4 leads to the formation of a cationic N-(2-propenyl)-aminocarbene complex 6a. Protonation of 4 with trifluoroacetic acid results in a ring contraction to give the four-membered metallacycles 7. X-ray data are reported for prototypes (Z)-4c and 6a.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240816
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  • 3
    Electronic Resource
    Electronic Resource
    Organische Synthesen mit Übergangsmetallkomplexen, 36: Funktionalisierte Tri(methylen)methan-Chrom- und Eisenkomplexe durch Addition von Allenen an M = C-Bindungen von Carbenkomplexen (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 1977-1982 
    Details
    ISSN: 0009-2940
    Keywords: Tri(methylene)methane chromium and iron complexes ; Allenes, insertion into M=C bonds of carbene complexes ; Metathesis of allenes ; 2- and 3-Methylenemetallacyclobutanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Organic Syntheses via Transition Metal Complexes, 36.  -  Monofunctional Tri(methylene)methane Chromium and Iron Complexes by Addition of Allenes to M = C Bonds of carbene ComplexesThe reaction of carbenechromium and -iron complexes 1a and 1b with monofunctional allenes H2C=C=CH—CH2Y 2 (Y = OH, CO2Et, CH2OH) leads to the formation of tri(methylene)-methane complexes 3 in good yields with insertion of 2 into the M=C bond of 1. The stereochemistry of this key reaction is markedly influenced by the metal moiety. Thus, with the (octahedral) chromium complex 1a only one stereoisomer 3-A is obtained, but with the (trigonal-bipyramidal) iron complex 1b a mixture of diastereomers 3-A-C is formed. On the other hand, the iron complex 1a yields 3 as the only product, while the chromium complex 1b in addition to 3 also gives an enol ether 4 by a metathesis reaction.
    Notes: Durch Umsetzung von Carbenchrom- und -eisenkomplexen 1a bzw. 1b mit funktionalisierten Allenen H2C=C=CH—CH2Y 2 (Y = OH, CO2Et, CH2OH) wurden unter Insertion von 2 in die M=C-Bindung von 1 Tri(methylen)methan-Komplexe 3 in guten Ausbeuten erhalten. Die Stereochemie dieser Schlüsselreaktion hängt stark vom jeweiligen Metallrest ab. Beim (oktaedrischen) Chromkomplex 1a entsteht mit hoher Selektivität jeweils nur ein Stereoisomer 3-A, beim (trigonal-bipyramidalen) Eisenkomplex hingegen ein Gemisch aus Diastereomeren 3-A-C. Andererseits bildet der Carbeneisenkomplesx 1b mit 2 selektiv nur Tri(methylen)methan-Komplex 3, der Carbenchromkomplex 1a hingegen zusätzlich ein Metatheseprodukt 4.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891221024
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  • 4
    Electronic Resource
    Electronic Resource
    Organische Synthesen mit Übergangsmetall-Komplexen, 56 Homopyrrole und Dihydropyridine aus N-Vinylaminocarben-Eisenkomplexen und Alkinen durch Cyclisierung intermediärer 5-Aza-1-metalla-1,3,6-triene (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 2595-2602 
    Details
    ISSN: 0009-2940
    Keywords: Homopyrroles, mono- and bicyclic ; [3 + 2] Cycloadditions of N-vinylaminocarbene iron complexes to alkynes ; 5-Aza-1-ferra-1,3,6-trienes ; Intramolecular cyclopropanation, metal-induced ; 2H-Pyrrolium tricarbonyl iron complexes ; Pyridine, 1,2-dihydro-, tricarbonyl iron complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organic Syntheses via Transition Metal Complexes, 561). - Homopyrroles and Dihydropyridines from N-Vinylamino-carbene Iron Complexes and Alkynes by Cyclisation of Intermediate 5-Aza-1-metalla-1,3,6-trienes2,3-Homopyrroles 5 and dihydropyridines 7, 8 are obtained by the light-induced addition of alkynes 4a - d (RC = CR1; R, R1 = H, CH3, C6H5, CO2CH3) to the N-vinylaminocarbene iron complex (= 3-aza-1-ferra-1,4-diene) 3. The formation of the N-heterocycles 5 and 7 as well as that of the pyrrolium carbonylferrates 6 can be explained by assuming the chelated 5-aza-1-ferra-1,3,6-trienes A to be key intermediates in this reaction. Stereochemical considerations lead to the conclusion that the ring expansion of the 4 1/2-membered ring of 3 to the 6 1/2-membered ring of A occurs without prior ≡ decomplexation by the insertion of a C = C unit into the M = C bond. NMR measurements and MNDO calculations suggest that the bicyclic homopyrroles 5 are in equilibrium with the novel monocyclic homopyrrole species 9. The structure of 6c has been established by X-ray diffraction analysis.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911241132
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