Anti-Markownikow-Hydroaminierung terminaler Alkine

Tillack, Annegret; Castro, Ivette Garcia; Hartung, Christian G.; Beller, Matthias

doi:10.1002/1521-3757(20020715)114:14<2646::aid-ange2646>3.0.co;2-a

Cited by 48 publications

(11 citation statements)

References 7 publications

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“…In contrast, reactions employing the arylalkynes 34± 36 always favor formation of the anti-Markovnikov regioisomers 41±45 a (entries 6± 10). The best anti-Markovnikov regioselectivities (> 99:1) are generally observed with the sterically demanding amine tertbutylamine (3) (entries 4, 7, and 8, Table 3), which is in agreement with reports by Beller et al [12] However, lower regioselectivities (1.5±4.5:1) were observed with arylamine 2 or the sterically less demanding alkylamine 4. Comparison of the 4methoxy-and 4-chloro-substituted phenylacetylenes 35 and 36 indicates that these substituents do not significantly change the behavior of the alkynes.…”

Section: Resultssupporting

confidence: 90%

[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

Heutling

Pohlki

Doye

2004

Chemistry A European J

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[Ind(2)TiMe(2)] (Ind=indenyl) is a highly active and general catalyst for the intermolecular hydroamination of alkynes. It catalyzes the reaction of primary aryl-, tert-alkyl-, sec-alkyl-, and n-alkylamines with internal and terminal alkynes. In the case of unsymmetrically substituted 1-phenyl-2-alkylalkynes, the reactions occur with modest to excellent regioselectivities, whereby formation of the anti-Markovnikov regioisomers is favored. While the major product of hydroamination reactions of terminal arylalkynes is always the anti-Markovnikov isomer, alkylalkynes react with arylamines to preferably give the Markovnikov products. To achieve reasonable rates for the addition of sterically less hindered n-alkyl- and benzylamines to alkynes, these amines must be added slowly to the reaction mixtures. This behavior is explained by the fact that the catalytic cycle proposed on the basis of an initial kinetic investigation includes the possibility that the rate of the reaction increases with decreasing concentration of the employed amine. Furthermore, no dimerization of the catalytically active imido complex is observed in the hydroamination of 1-phenylpropyne with 4-methylaniline in the presence of [Ind(2)TiMe(2)] as catalyst. In general, a combination of [Ind(2)TiMe(2)]-catalyzed hydroamination of alkynes with subsequent reduction leads to the formation of secondary amines with good to excellent yields. Particularly impressive is that [Ind(2)TiMe(2)] makes it possible for the first time to perform the reactions of n-alkyl- and benzylamines with 1-phenylpropyne in a highly regioselective fashion.

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Section: Resultssupporting

confidence: 90%

[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

Heutling

Pohlki

Doye

2004

Chemistry A European J

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“…The study of group 4 metal‐catalysed reactions of hydrazines with unsaturated organic substrates has almost exclusively focussed on titanium 1. The hydrohydrazination of alkynes,2 its extension to a catalytic three‐component iminohydrazination,3 as well as its development into an efficient metal‐catalysed indole synthesis are prominent examples 4. Until very recently, there was only one example of a heavier group 4 hydrazido complex, [Cp 2 Zr(N 2 Ph 2 )(dmap)] (Cp: C 5 H 5 , dmap: 4‐dimethylaminopyridine), which had been reported by Bergman and co‐workers in 1991 5.…”

Section: Introductionmentioning

confidence: 99%

Bonding and Bending in Zirconium(IV) and Hafnium(IV) Hydrazides

Herrmann

Lloret‐Fillol

Gehrmann

et al. 2008

Chemistry A European J

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Reaction of the dichloro complexes [M(N(2) (TBS)N(py))Cl(2)] (M=Zr: 1, Hf: 2; TBS: tBuMe(2)Si; py: pyridine) with one molar equivalent of LiNHNPh(2) gave mixtures of the two diastereomeric chlorohydrazido(1-) complexes [M(N(2) (TBS)N(py))(NHNPh(2))Cl] (M=Zr: 3 a,b, Hf: 4 a,b) in which the diphenylhydrazido(1-) ligand adopts a bent kappa(1) coordination. This mixture of isomers could be cleanly converted into the deep green diphenylhydrazido(2-) complexes [Zr(N(2) (TBS)N(py))(NNPh(2))(py)] (5) and [Hf(N(2) (TBS)N(py))(NNPh(2))(py)] (6), respectively, by dehydrohalogenation with lithium hexamethyldisilazide (LiHMDS) in the presence of one molar equivalent of pyridine. Both complexes contain a linearly coordinated hydrazinediide for which a DFT-based frontier orbital analysis established bonding through one sigma and two pi orbitals. A high polarity of the M=N bond was found, in accordance with the description of hydrazinediide(2-) acting as a six-electron donor ligand. The pyridine ligand in [M(N(2) (TBS)N(py))(NNPh(2))(py)] (M=Zr: 5, Hf: 6) is substitutionally labile as established by line-shape analysis of the dynamic spectra (DeltaG(not equal)=19 kcal mol(-1)). A change in denticity of the hydrazido unit from kappa(1) to kappa(2) was studied by DFT methods. Both forms are calculated to be very close in energy and are only separated by shallow activation barriers, which supports the notion of a rapid kappa(1) to kappa(2) interconversion. This process is believed to happen early on in the N-N scission in the presence of coupling reagents. Frontier orbital and natural population analyses suggest that a primarily charge-controlled nucleophilic attack at N(alpha) is unlikely whereas interaction with an electrophile could play an important role. This hypothesis was tested by the reaction of 5 and 6 with one molar equivalent of B(C(6)F(5))(3) to give [Zr(N(2) (TBS)N(py))(NNPh(2)){B(C(6)F(5))(3)}] (7) and [Hf(N(2) (TBS)N(py))(NNPh(2)){B(C(6)F(5))(3)}] (8). In these products, B(C(6)F(5))(3) becomes attached to the N(alpha) atom of the side-on bound hydrazinediide and there is an additional interaction of an ortho-F atom of a C(6)F(5) ring with the metal centre.

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“…Based on this simple substitution reaction, Cp 2 Ti(η 2 ‐btmsa) and similar complexes were applied as excellent sources for the generation of the very reactive coordinatively and electronically unsaturated complex fragments [Cp′ 2 M]. These were used in many synthetic and catalytic reactions, summarized before in several papers and some reviews . Nevertheless, some very view examples exist in which the substitution of the bis(trimethylsilyl)acetylene ligand did not work and a coupling of the alkyne with other substrates was found …”

Section: Examples For Substrate Substitutionmentioning

confidence: 99%

“…To realize such effective stoichiometric and catalytic reactions it is generally very important to form coordinatively and electronically unsaturated complex fragments. For this the group 4 metallocene bis(trimethylsilyl)acetylene complexes became more and more interesting during the last years in stoichiometric [2–22] and catalytic reactions. Typical examples for several methods to obtain compounds of this type were published and will be described in detail in this account…”

Section: Introductionmentioning

confidence: 99%

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

Rosenthal

2019

ChemistryOpen

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Active species for synthetic and catalytic applications are formed from well defined complexes or mixtures of compounds. For group 4 metallocenes, three pathways for the formation of the reactive complex fragment [Cp′ 2 M] are known: (i) reductive mixtures and well defined complexes which are able to form the metallocene fragments either by (ii) addition or (iii) substitution reactions. In this account for each of theses systems (i)–(iii) a prominent example will be discussed in detail, (i) the Negishi reagent Cp 2 ZrCl 2 /n‐BuLi, (ii) bis(η 5 : η 1 ‐pentafulvene) complexes and (iii) metallocene bis(trimethylsilyl)acetylene complexes, to show the advantages and the disadvantages for each of these methods for synthetic applications. This account summarizes some main advantages of group 4 metallocene bis(trimethylsilyl)acetylene complexes as metallocene generating agents over other synthetically used systems. For each of the special purposes, all described systems have advantages as well as disadvantages. The aim of this overview is to help synthetic chemists in selecting the most effective system on the basis of [Cp′ 2 M] (M=Ti, Zr) for synthetic or catalytic puposes.

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Anti-Markownikow-Hydroaminierung terminaler Alkine

Cited by 48 publications

References 7 publications

[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

Bonding and Bending in Zirconium(IV) and Hafnium(IV) Hydrazides

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

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Anti-Markownikow-Hydroaminierung terminaler Alkine

Cited by 48 publications

References 7 publications

[Ind2TiMe2]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

[Ind2TiMe2]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

Bonding and Bending in Zirconium(IV) and Hafnium(IV) Hydrazides

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

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[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes

[Ind₂TiMe₂]: A General Catalyst for the Intermolecular Hydroamination of Alkynes