Scandium-Catalyzed Intramolecular Hydroamination. Development of a Highly Active Cationic Catalyst

Lauterwasser, Frank; Hayes, Paul G.; Bräse, Stefan; Piers, Warren E.; Schafer, Laurel L.

doi:10.1021/om0498551

Cited by 162 publications

(64 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…[36,42,54,60,61,65,68,75] For other organic transformations, two instructive examples have recently appeared in the literature. [77,90] Cationic lanthanide alkyl derivatives as homogeneous catalysts appear to be generally superior to their neutral precursors due to their increased electrophilicity towards substrate molecules.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

2005

View full text Add to dashboard Cite

This contribution is dedicated to Dick Schrock on the occasion of his 60th birthday.Abstract: Cationic alkyl complexes of the rare-earth metals [LnR m ; L ¼ Lewis base) were virtually unknown species until recently. Because of their increased Lewis acidity/electrophilicity they should have considerable potential as homogeneous catalysts in olefin polymerization and in organic transformations. They can be generated by treating the neutral rare-earth metal precursors containing at least two alkyl groups R with suitable Lewis or Brønsted acids in the presence of weakly coordinating anions. Not only monocationic but also dicationic alkyl derivatives have been shown to be accessible. In the context of modeling homogeneous ethylene polymerization using a mixture consisting of LnR 3 /AlR 3 /[NMe 2 HPh][B(C 6 F 5 ) 4 ], such dications were discovered. Some thermally robust examples of mono-and dicationic alkyl complexes have been structurally characterized as solvent-separated ion pairs. Neutral and monoanionic macrocycles such as crown ethers or aza-crown ethers as well as amidinato, b-diketiminato, and substituted cyclopentadienyl ligands are suitable ancillary ligands to stabilize the cationic alkyl fragments.

show abstract

Section: Resultsmentioning

confidence: 99%

“…Since the stoichiometric reaction of the cationic scandium complex with an aminoalkene gives a cationic pyrrolidinato complex, as characterized by NMR spectroscopy, the catalytically active species appears to be an amido cation. [90] …”

Section: Intramolecular Hydroaminationmentioning

confidence: 99%

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

2005

View full text Add to dashboard Cite

show abstract

“…[1] The intramolecular hydroamination constitutes a particularly powerful and concise route to functionalised nitrogen heterocycles. Initially dominated by the discovery of organolanthanide catalysts, [1k, 2] present-day intramolecular hydroamination research activities are wide ranging, covering the entire Periodic Table, from alkaline-earth metals, [3] early dblock metals, [4,5] 4f-block elements [2] and 5f-block elements [6] to late d-block metals [7,8] and coinage metals. [7b, n, 9] On the basis of the comprehensive mechanistic exploration of organolanthanide-mediated intramolecular hydroamination [1k] two distinct mechanistic pathways have emerged over the years, which have been subsequently adapted to organoactinide, zirconium and alkaline-earth metal catalyst systems.…”

Section: Introductionmentioning

confidence: 99%

Does a Concerted Non‐Insertive Mechanism Prevail over a σ‐Insertive Mechanism in Catalytic Cyclohydroamination by Magnesium Tris(oxazolinyl)phenylborate Compounds? A Computational Study

Tobisch

2011

Chemistry A European J

View full text Add to dashboard Cite

The present study comprehensively explores alternative mechanistic pathways for intramolecular hydroamination of 2,2-dimethyl-4-penten-1-amine (1) by [{To(M)}MgMe] (To(M)=tris(4,4-dimethyl-2-oxazolinyl)phenylborate) (2) with the aid of density functional theory (DFT) calculations. A single-step amidoalkene → cycloamine conversion through a concerted proton transfer associated with N-C ring closure has been explored as one possible mechanism; its key features have been described. This non-insertive pathway evolves via a six-centre TS structure featuring activation of the olefin unit towards nucleophilic amido attack outside the immediate vicinity of the metal centre by amino proton delivery and describes a viable mechanistic variant for alkaline-earth metal-mediated aminoalkene hydroamination. However, herein is presented sound evidence for the operation of the Mg-N amido σ-bond insertive mechanism, its turnover-limiting activation barrier is found to be 5.0 kcal mol(-1) lower than for the non-insertive mechanism, for the cyclohydroamination of 2,2-disubstituted 4-aminoalkenes by a [{To(M)}Mg-NHR] catalyst. The operative mechanism involves rapid equilibria of the {To(M)}Mg-amidoalkene resting state 3 with its amine adduct, easily accessible and thermodynamically disfavoured, hence reversible, 1,2-olefin insertion into the Mg-N amido σ-bond with ring closure at 3, linked to turnover-limiting Mg-C azacycle tether aminolysis by an adduct substrate molecule, followed by facile cycloamine liberation to regenerate the active catalyst species 3. The following aspects are in support of this scenario: 1) the derived rate law is consistent with the experimentally obtained empirical rate law; 2) the reasonable agreement between the computationally estimated and the observed value of the primary KIE; 3) the assessed effective activation barrier for turnover-limiting aminolysis matches empirically determined Eyring parameters remarkably well; and 4) the observed resistance of isolated 3 to undergo amidoalkene cycloamine/cycloamido transformation until further quantities of substrate is added is consistently explained. The herein unveiled insights into the structure-reactivity relationships will undoubtedly govern the rational design of alkaline-earth metal-based catalysts and likely facilitate further advances in the area.

show abstract

“…在另一例报道中, 以钪为中心金属的离子型催化剂 16b 的催化效率也同样优于中性分子 16a(图 3) [70] . 如前所述, 配体的空间位阻越小, 给电子活性越低, 催化剂的催化活性就越高 [56,57] .…”

Section: 碱土金属催化的分子内氢胺化反应unclassified

Research Progress in Non-noble Metals Catalyzed Hydroamination of Alkyenes and Alkynes

Wang¹,

Cui²

2016

Chin. J. Org. Chem.

6
0
0
0

View full text Add to dashboard Cite

show abstract

Scandium-Catalyzed Intramolecular Hydroamination. Development of a Highly Active Cationic Catalyst

Abstract: The scandium-catalyzed intramolecular hydroamination of alkynes and alkenes is reported. Complex structure/catalyst activity investigations resulted in the identification of a highly catalytically active cationic, β-diketiminato scandium complex.

Cited by 162 publications

References 36 publications

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Cationic Alkyl Complexes of the Rare‐Earth Metals: Synthesis, Structure, and Reactivity

Does a Concerted Non‐Insertive Mechanism Prevail over a σ‐Insertive Mechanism in Catalytic Cyclohydroamination by Magnesium Tris(oxazolinyl)phenylborate Compounds? A Computational Study

Research Progress in Non-noble Metals Catalyzed Hydroamination of Alkyenes and Alkynes

Contact Info

Product

Resources

About