Catalytic and Atom‐Economic C−C Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation

DiPucchio, Rebecca C.; Roşca, Sorin-Claudiu; Schafer, Laurel L.

doi:10.1002/ange.201712668

Cited by 15 publications

(6 citation statements)

References 81 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The catalytic addition of amines to alkenes, hydroaminoalkylation, enables the selective formation of functionalized norbornene monomers in a single, atom-economic catalytic reaction while avoiding waste generation or the need for directing/protecting groups. − This approach offers advantages over alternative multistep protocols that rely on stoichiometric transformations and the concomitant formation of byproducts. ,, Ready access to monomers suitable for ROMP offers an attractive 100% atom-economic route for the synthesis of amine-containing polymers (Scheme ). However, easily assembled hydroaminoalkylation catalyst systems for high-yielding, multigram-scale syntheses of such monomers are unknown, and ROMP of unprotected amine-containing monomers has rarely been reported. ,, …”

Section: Introductionmentioning

confidence: 99%

Dynamic Cross-Linking of Catalytically Synthesized Poly(Aminonorbornenes)

et al. 2020

Self Cite

View full text Add to dashboard Cite

Amine-functionalized polymeric materials have a wide variety of applications; however, the preparation of these materials is often plagued by laborious, multistep synthetic routes. Herein, a modified and improved synthetic protocol utilizes the hydroaminoalkylation reaction to catalytically assemble amine-functionalized monomers on a gram scale with 100% atom economy. Combined with ring-opening metathesis polymerization (ROMP), amine-functionalized polymers with varying electronic properties have been synthesized. Extensive rheological characterizations show that modification of the electronic properties of the amine substituent influences the bulk material properties through modification of hydrogen bonding and π-stacking interactions to afford dynamic cross-linking within the polymeric material. Tertiary amine-containing polymers display distinct rheological properties that differ from those of polymers with pendant hydrogen-bond-donating secondary amines. The profound viscoelastic effects that result from the incorporation of tunable dynamic interactions are presented.

show abstract

Section: Introductionmentioning

confidence: 99%

Dynamic Cross-Linking of Catalytically Synthesized Poly(Aminonorbornenes)

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…The substantial improvement of reactivity with this modification hinted at the potential for improved catalysis by using ligand design features that promote the formation of electrophilic metal centers. These pioneering contributions inspired the development of a variety of metal complexes for this transformation. ,− …”

Section: Introductionmentioning

confidence: 99%

Ta-Catalyzed Hydroaminoalkylation of Alkenes: Insights into Ligand-Modified Reactivity Using DFT

et al. 2018

Self Cite

View full text Add to dashboard Cite

Density functional theory (DFT) calculations were performed to probe the mechanism of tantalum-catalyzed hydroaminoalkylation, a reaction that affords Csp3–Csp3 bond formation via α-alkylation of a secondary amine with an alkene. Electronic effects in catalyst design were probed to reveal key features in the energy profile of the proposed mechanism, corroborating experimental trends in which electrophilic metal centers demonstrate enhanced reactivity. Modeling of the energy profile with an N,O-chelating amidate Ta catalyst (I) revealed profound differences in relative energetics, rationalizing improvements that have been observed using sterically and electronically varied ligands. N,O-Chelating ligands electronically promote preferential reactivity in the equatorial plane. The turnover-limiting step can be completely changed depending upon the ligand; for sterically bulky monoamidate complexes, the protonolysis of an intermediate metallacycle is the turnover-limiting step rather than C–H activation, as has been found for systems lacking steric bulk. Unproductive off-cycle pathways were also modeled to compare with experimental studies. These insights contribute to a theoretical understanding of key features in ligand design for developing improved catalysts for hydroaminoalkylation.

show abstract

“…Previous results have shown an enhanced reactivity of organometallic precursors over amido precursors, 46,57 as this eliminates the possibility of reversible amido exchange reactions that may inhibit catalyst activity. 58 Recently, Ta(CH 2 SiMe 3 ) 3 Cl 2 has been shown to be very effective for in situ catalyst preparation by salt metathesis.…”

Section: ■ Results and Discussionmentioning

confidence: 91%

“…On the basis of previous experimental observations in ureate systems versus amidate systems, one notes that altering the N,O-ligand backbone has a pronounced effect on the catalytic activity of the corresponding catalyst. 35,46 To explore the importance of the N,O-chelate, related N,N-chelating ligands were evaluated as hydroaminoalkylation catalysts. Specifically, we turned our attention to guanidinate ligands.…”

Section: ■ Introductionmentioning

confidence: 99%

Guanidinate Early-Transition-Metal Complexes: Efficient and Selective Hydroaminoalkylation of Alkenes

2022

Self Cite

View full text Add to dashboard Cite

The influence of a series of N,N-chelating guanidinate ligands on the reactivity of in situ generated tantalum complexes for the intermolecular hydroaminoalkylation of amines has been explored. Increased conversion was observed with the sodium salt of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBDNa) paired with the tantalum precursor Ta(CH2SiMe3)3Cl2 at 110 °C. Terminal alkenes underwent hydroaminoalkylation with a variety of secondary amine substrates to give substituted secondary amine products. Mono- and bis(guanidinate) tantalum complexes were prepared, and their structures were investigated. Importantly, the guanidinate ligand could be alkylated in the β position using Ta(NMe2)5 as a precatalyst to give the linear regioisomer as the major product, and this substituted ligand gave improved hydroaminoalkylation conversion in comparison to the parent ligand.

show abstract

Catalytic and Atom‐Economic C−C Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation

Cited by 15 publications

References 81 publications

Dynamic Cross-Linking of Catalytically Synthesized Poly(Aminonorbornenes)

Dynamic Cross-Linking of Catalytically Synthesized Poly(Aminonorbornenes)

Ta-Catalyzed Hydroaminoalkylation of Alkenes: Insights into Ligand-Modified Reactivity Using DFT

Guanidinate Early-Transition-Metal Complexes: Efficient and Selective Hydroaminoalkylation of Alkenes

Contact Info

Product

Resources

About