Reaction of Zirconacyclopentadienes with Ethynylferrocenes

Dufková, Lenka; Matsumura, Hiroshi; Nečas, David; Štěpnička, Petr; Uhlı́k, Filip; Kotora, Martin

doi:10.1135/cccc20040351

Cited by 17 publications

(5 citation statements)

References 34 publications

(15 reference statements)

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“…The reaction of different zirconacyclopentadienes with alkynes bearing at least one electron-withdrawing group attached to the triple bond to afford [2 + 2 + 2] cycloaddition reactions in the presence of CuCl has been studied by the same and other research groups. Haloterphenyl derivatives, 217 haloterphenyl compounds with chiral backbones, 218 polyacenes, 219 highly substituted phenylferrocenes, 220 and sterically hindered biaryls 221 were prepared using this process.…”

Section: Palladium Complexesmentioning

confidence: 99%

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Mechanistic Studies of Transition-Metal-Catalyzed [2 + 2 + 2] Cycloaddition Reactions

2020

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The development of catalytic methodologies involving the formation of C−C bonds to enable the generation of cyclic systems constitutes a field of great relevance in synthetic organic chemistry. One paradigmatic process to accomplish this goal efficiently is the transition-metal-catalyzed [2 + 2 + 2] cycloaddition reaction, since it permits the formation of a wide range of highly functionalized 6-membered carbo-and heterocyclic molecules in a single step with high efficiency and perfect atom economy. A key feature of these transformations is the mechanistic pathway that they follow, since a deep knowledge of this mechanism may enable us to understand and improve the efficiency of the reaction. This review covers the mechanistic aspects, studied both from theoretical and experimental points of view, of the transition-metal-catalyzed [2 + 2 + 2] cycloaddition reaction involving all kinds of unsaturated substrates with metals such as Co, Ni, Ru, Rh, Ir, Pd, Zr, Ti, Ta, and Nb. A thorough overview is undertaken, from the seminal studies until the present day, of the key mechanistic aspects that influence the reactivity and selectivity of the reaction, comparing the involvement of different unsaturated substrates as well as the different transition metals used.

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Section: Palladium Complexesmentioning

confidence: 99%

“…Kotora et al also used [NiX 2 (PPh 3 ) 2 ] (X = Cl or Br) for the cycloaddition of zirconacyclopentadienes with alkynes such as ethynylferrocenes 220 and arylpropionates. 221 In the case of ferrocenyl derivatives, no electron-withdrawing group was required in the third alkyne to make the process efficient.…”

Section: Palladium Complexesmentioning

confidence: 99%

Mechanistic Studies of Transition-Metal-Catalyzed [2 + 2 + 2] Cycloaddition Reactions

2020

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“…The reductive coupling of alkynes by zirconocene is an important carbon−carbon bond forming reaction. − The resulting zirconacyclopentadienes are useful precursors to a wide range of organic molecules including (for example) dienes, arenes, − cyclopentadienes, − cyclopentadienones, thiophenes, , phospholes, thiophene oxides, and bicyclic compounds via electrophilic substitution of the metal center. When unsymmetrical alkynes are coupled, an important factor that determines the structure of the product is the regiochemistry for the alkyne coupling at zirconium, which is known to be sensitive to both steric and electronic factors.…”

Section: Introductionmentioning

confidence: 99%

Mesityl Alkyne Substituents for Control of Regiochemistry and Reversibility in Zirconocene Couplings: New Synthetic Strategies for Unsymmetrical Zirconacyclopentadienes and Conjugated Polymers

et al. 2009

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Reaction of 2 equivs of MesC[triple bond]CPh with Cp(2)Zr(eta(2)-Me(3)SiC[triple bond]CSiMe(3))(pyr) afforded the zirconacyclopentadiene Cp(2)Zr[2,5-Ph(2)-3,4-Mes(2)C(4)]. The regiochemistry of this isomer (betabeta with respect to the mesityl substituents) was determined through single-crystal X-ray analysis and 2D (NOESY, HSQC, HMBC) NMR experiments. This selectivity is attributed largely to a steric-based directing effect of the o-methyl ring substituents since coupling of 1,3-dimethyl-2-(phenylethynyl)benzene with zirconocene gave a single regioisomer (o-xylyl groups in both beta-positions) while coupling of 1,3-dimethyl-5-(phenylethynl)benzene gave a statistical distribution of zirconacyclopentadiene regioisomers. The coupling reaction of 2 equivs of MeC[triple bond]CMes or PrC[triple bond]CMes with Cp(2)Zr(eta(2)-Me(3)SiC[triple bond]CSiMe(3))(pyr) at ambient temperature gave the betabeta regioisomers, Cp(2)Zr[2,5-Me(2)-3,4-Mes(2)C(4)] and Cp(2)Zr[2,5-Pr(2)-3,4-Mes(2)C(4)], respectively, as the major products. Heating solutions of these zirconacycles at 80 degrees C for several hours resulted in an increase in the amount of the unsymmetrical product. For reaction mixtures of PrC[triple bond]CMes and Cp(2)Zr(eta(2)-Me(3)SiC[triple bond]CSiMe(3))(pyr) the major (and apparently thermodynamic) product under these reaction conditions was Cp(2)Zr[2,4-Mes(2)-3,5-Pr(2)C(4)]. The steric strain in the mesityl-substituted zirconacycles allowed for facile substitution reactions of MesC[triple bond]CPh or PrC[triple bond]CMes by less bulky alkynes (i.e., tolan and 3-hexyne) to give the unsymmetrical ziconacyclopentadienes Cp(2)Zr[2,4,5-Ph(3)-3-MesC(4)], Cp(2)Zr[2-Ph-3-Mes-4,5-Et(2)C(4)], and Cp(2)Zr[2-Pr-3-Mes-4,5-Ph(2)C(4)]. Reaction of a mesityl-terminated diyne containing a rigid dihexylfluorenylene spacer with zirconocene afforded poly(p-fluorenylenedienylene) after demetalation with benzoic acid.

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“…[9] This method has been successfully applied for the synthesis of polysubstituted aromatic compounds such as benzoheterocycles containing group 14 elements, [10] haloterphenyls, [11] haloterphenyls with chiral backbones, [12] perfluoroalkyl-substituted terphenyls, [13] polyacenes, [14] and ferrocenylalkynes. [15] There are several factors that favor the above method: firstly, zirconacyclopentadienes are easily prepared with a great variety of substituents and they are stable at room temperature, and secondly, arylalkynes can be easily prepared from commonly accessible starting material. Additionally, both CuCl and NiBr 2 (PPh 3 ) 2 are stable and cheap compounds.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Sterically Hindered Biaryls by Zr‐Mediated Co‐cyclotrimerization of Alkynes

2005

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Treatment of zirconacyclopentadienes with ortho‐substituted arylpropynoates in the presence of stoichiometric amounts of CuCl or NiBr2(PPh3)2 represents a novel approach to the synthesis of biaryls, formed in good yields. The CuCl‐mediated reaction proceeded through two reaction mechanisms, also affording Dewar benzenes together with the corresponding biaryls. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Reaction of Zirconacyclopentadienes with Ethynylferrocenes

Cited by 17 publications

References 34 publications

Mechanistic Studies of Transition-Metal-Catalyzed [2 + 2 + 2] Cycloaddition Reactions

Mechanistic Studies of Transition-Metal-Catalyzed [2 + 2 + 2] Cycloaddition Reactions

Mesityl Alkyne Substituents for Control of Regiochemistry and Reversibility in Zirconocene Couplings: New Synthetic Strategies for Unsymmetrical Zirconacyclopentadienes and Conjugated Polymers

Synthesis of Sterically Hindered Biaryls by Zr‐Mediated Co‐cyclotrimerization of Alkynes

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