Der Mechanismus der titankatalysierten Hydroaminoalkylierung von Alkenen

Prochnow, Insa; Zark, Patrick; Müller, Thomas; Doye, Sven

doi:10.1002/ange.201101239

Cited by 44 publications

(13 citation statements)

References 32 publications

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“…To this end, styrenes were reacted with p ‐methoxy‐ N ‐methylaniline. In contrast to reports using Group 4 catalysts,4e,g in this case, electron‐rich and electron‐deficient styrenes are very well tolerated, although prolonged reaction times are required (entries 7–10, 3 p – 3 s ). Here again, performing the reaction at 50 °C shortens the required reaction time.…”

Section: Methodscontrasting

confidence: 80%

Phosphoramidate Tantalum Complexes for Room‐Temperature CH Functionalization: Hydroaminoalkylation Catalysis

et al. 2013

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Amines are critical functional groups that are incorporated into many biologically active compounds and functional materials of importance to the biomedical, agrochemical and fine-chemical industries. [1] An idealized synthetic approach for the preparation of this important class of compounds would take advantage of the direct and byproduct free conversion of feedstock alkenes directly into unprotected amines with good regio-and stereoselectivity under mild reaction conditions. These goals could be realized with early transition metal catalyzed hydroaminoalkylation (Scheme 1), a CÀH functionalization reaction a to nitrogen that results in selective C À C bond formation. [2, 3] However, to date, all promising Group 4 and 5 metal complexes for this transformation demand harsh reaction conditions. [4,5] The identification of a system that can be used with mild reaction conditions is desirable. Here we show that by using a sterically demanding, N,O-chelating, electron-withdrawing phosphoramidate as an easily installed auxiliary ligand, room-temperature alkene hydroaminoalkylation can be achieved for the first time.Unlike late transition metal catalysts (Ir, Ru) [6,7] for this reaction, early transition metal catalysts (Ti, [4] Zr, [4a] Ta, [5] Nb, [5e-g] ) do not require a removable directing group or activated alkene substrates. Hydroaminoalkylation results in unprotected amines ready for further functionalization. This transformation gives selectively substituted amines in a single and atom-economic catalytic reaction, using inexpensive early transition metals of low toxicity. Thus, hydroaminoalkylation is an excellent reaction to target for advances in green chemistry.Ligand screening investigations by Herzon and Hartwig have shown that electron-withdrawing chloride ligands enhance reactivity, such that select substrate combinations yield products at 90 8C. [5b] Notably, the more challenging dialkylamine substrates required temperatures of 150 8C and thermally polymerizable styrene derivatives were not reported. [4b] Herein, we show that our phosphoramidate-ClTaMe 3 precatalyst is easily synthesized and can achieve roomtemperature hydroaminoalkylation with a broad range of substrates.

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Section: Methodscontrasting

confidence: 80%

Phosphoramidate Tantalum Complexes for Room‐Temperature CH Functionalization: Hydroaminoalkylation Catalysis

et al. 2013

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“…The active species of the mechanism is commonly assumed to be an azametallacyclopropane because they promote alkylation on the α‐position of the amine. A putative catalytic hydroaminoalkylation cycle has been proposed but has only been supported by a limited number of experiments 8b,11. In 1982, Nugent et al.…”

Section: Introductionmentioning

confidence: 99%

“…investigated the α‐deuteration of dimethylamine by reversible α‐metallation–demetallation reaction 12. More recently, Hultzech8c and Doye11 conducted kinetic studies on niobium‐ and titanium‐based catalysts. Elimination of an amine from a metal bis(amide) precursor produces an intermediate that is classically assumed to be a metallaaziridine 13.…”

Section: Introductionmentioning

confidence: 99%

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Isolation and Characterization of Well‐Defined Silica‐Supported Azametallacyclopentane: A Key Intermediate in Catalytic Hydroaminoalkylation Reactions

et al. 2015

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“…9,10 In such a way, by β‐C–H activation of titanium amides ( B ), the formation of η 2 ‐imine complexes ( C ) that more or less exhibit a titanaaziridine structure ( D ) should be possible (Figure 2). Intermediates of type C as well as D are discussed as important key compounds in the hydroaminoalkylation of alkenes 11…”

Section: Introductionmentioning

confidence: 99%

Bulky Titanium Amides: C–H Bond Activation under Mild Conditions

et al. 2014

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The bulky titanium monoamido complex Cl 3 TiNCy 2 (1) was synthesized from TiCl 4 and dicyclohexylamine (Cy 2 NH). The solid-state structure of 1 demonstrates a close intramolecular contact between the metal centre and one ipso carbon atom of the amido ligand. This contact may indicate an agostic interaction analogous to those of transition metal alkyl compounds. The alteration of the coordination sphere of 1 with neutral ligands [pyridine (2), 2,2Ј-bipyridyl (3), N,N,NЈ,NЈtetramethylethane-1,2-diamine (tmeda, 4), and 1,2-bis(dimethylphosphanyl)ethane (dmpe, 5)] results in octahedral compounds with a meridional arrangement of the ligands. The solid-state structure of 5 reveals a significantly closer contact between the titanium atom and one ipso carbon atom of the ligand. The magnesium reduction of 1 in the presence of adamantylidenepentafulvene yields the dark green com-

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Der Mechanismus der titankatalysierten Hydroaminoalkylierung von Alkenen

Cited by 44 publications

References 32 publications

Phosphoramidate Tantalum Complexes for Room‐Temperature CH Functionalization: Hydroaminoalkylation Catalysis

Phosphoramidate Tantalum Complexes for Room‐Temperature CH Functionalization: Hydroaminoalkylation Catalysis

Isolation and Characterization of Well‐Defined Silica‐Supported Azametallacyclopentane: A Key Intermediate in Catalytic Hydroaminoalkylation Reactions

Bulky Titanium Amides: C–H Bond Activation under Mild Conditions

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