Access to the most sterically crowded anilines <i>via</i> non-catalysed C–C coupling reactions

Vrána, Jan; Самсонов, М. А.; Němec, Vlastimil; Růžička, Aleš

doi:10.1039/c9cc09497k

Cited by 7 publications

(5 citation statements)

References 49 publications

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“…From the aforementioned insight for isolating the Cu–H monomer, we prepared IPr*CHPh 2 •HCl and IPr*CPh 3 •HCl on a gram scale (Figure A) in isolated yields of 65 and 82%, respectively (see the Supporting Information). Key to the synthesis of IPr*CPh 3 •HCl is accessing 2,6-dibenzhydryl-4-tritylaniline (71%) in two steps by reductive deoxygenation of (2-amino-1,3-phenylene)bis(diphenylmethanol) and alkylation of the resulting 2,6-dibenzhydrylaniline with Ph 3 COH (Figure A). Subsequently, a one-pot reaction of IPr*R•HCl, KN(SiMe 3 ) 2 , and CuCl in tetrahydrofuran (THF) at 25 °C produced the corresponding air-stable complexes (IPr*CHPh 2 )CuCl ( 1 ) and (IPr*CPh 3 )CuCl ( 2 ) in 50–60% isolated yield (Figure B).…”

Section: Resultsmentioning

confidence: 99%

“…This stoichiometric insertion is extended to catalytic hydroboration of internal alkenes. 28 and alkylation of the resulting 2,6dibenzhydrylaniline with Ph 3 COH (Figure 1A). Subsequently, a one-pot reaction of IPr*R•HCl, KN(SiMe 3 ) 2 , and CuCl in tetrahydrofuran (THF) at 25 °C produced the corresponding air-stable complexes (IPr*CHPh 2 )CuCl (1) and (IPr*CPh 3 )-CuCl (2) in 50−60% isolated yield (Figure 1B).…”

Section: ■ Introductionmentioning

confidence: 99%

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Isolation of a Cu–H Monomer Enabled by Remote Steric Substitution of a N-Heterocyclic Carbene Ligand: Stoichiometric Insertion and Catalytic Hydroboration of Internal Alkenes

et al. 2022

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Transient Cu–H monomers have long been invoked in the mechanisms of substrate insertion in Cu–H catalysis. Their role from Cu–H aggregates has been mostly inferred since ligands to stabilize these monomeric intermediates for systematic studies remain limited. Within the last decade, new sterically demanding N-heterocyclic carbene (NHC) ligands have led to isolable Cu–H dimers and, in some cases, spectroscopic characterization of Cu–H monomers in solution. We report an NHC ligand, IPr*R, containing para R groups of CHPh2 and CPh3 on the ligand periphery for the isolation of a Cu–H monomer for insertion of internal alkenes. This reactivity has not been reported for (NHC)CuH complexes despite their common application in Cu–H-catalyzed hydrofunctionalization. Changing from CHPh2 to CPh3 impacts the relative concentration of Cu–H monomers, rate of alkene insertion, and reaction of a trisubstituted internal alkene. Specifically, for R = CPh3, monomeric (IPr*CPh3)CuH was isolated and provided >95% monomer (10 mM in C6D6). In contrast, for R = CHPh2, solutions of [(IPr*CHPh2)CuH]2 are 80% dimer and 20% (IPr*CHPh2)CuH monomer at 25 °C based on 1H, 13C, and 1H–13C HMBC NMR spectroscopy. Quantitative 1H NMR kinetic studies on cyclopentene insertion into Cu–H complexes to form the corresponding Cu–cyclopentyl complexes demonstrate a strong dependence on the rate of insertion and concentration of the Cu–H monomer. Only (IPr*CPh3)CuH, which has a high monomer concentration, underwent regioselective insertion of a trisubstituted internal alkene, 1-methylcyclopentene, to give (IPr*CPh3)Cu(2-methylcyclopentyl), which has been crystallographically characterized. We also demonstrated that (IPr*CPh3)CuH catalyzes the hydroboration of cyclopentene and methylcyclopentene with pinacolborane.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Isolation of a Cu–H Monomer Enabled by Remote Steric Substitution of a N-Heterocyclic Carbene Ligand: Stoichiometric Insertion and Catalytic Hydroboration of Internal Alkenes

et al. 2022

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“…The authors have cited additional references within the Supporting Information. [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47] The calculations were performed on the computers of the Consortium des Équipements de Calcul Intensif en Fédération Wallonie Bruxelles (CÉCI) and particularly those of the Technological Platform of High-Performance Computing, which are supported by the F. R. S.-FNRS, the Walloon Region, the Université de Namur and the Université catholique de Louvain (Conventions No. U.G006.15, U.G018.19, U.G011.22, RW1610468, RW/GEQ2016, RW2110213 and 2.5020.11).…”

Section: Supporting Informationmentioning

confidence: 99%

Reactivity and Steric Parameters from 2D to 3D Bulky Pyridines: Increasing Steric Demand at Nitrogen with Chiral Azatriptycenes

Saida,

Mahaut,

Tumanov

et al. 2024

Angewandte Chemie

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Sterically hindered pyridines embedded in a three‐dimensional triptycene framework have been synthesized, and their resolution by chiral HPLC enabled access to unprecedented enantiopure pyridines exceeding the known steric limits. The design principles for new axially chiral pyridine derivatives are then described. To rationalize their associations with Lewis acids and transition metals, a comprehensive determination of the steric and electronic parameters for this new class of pyridines was performed. This led to the general parameterization of the steric parameters (percent buried volume %VBur, Tolman cone angle θ, and He8_steric descriptor) for a large set of two‐ and three‐dimensional pyridine derivatives. These parameters are shown to describe quantitatively their interactions with carbon‐ and boron‐centered Lewis acids and were used to predict the ΔG° of association with the prototypical B(C6F5)3 Lewis acid widely used in frustrated Lewis pair catalysis. This first parameterization of pyridine sterics is a fundamental basis for the future development of predictive reactivity models and for guiding new applications of bulky and chiral pyridines in organocatalysis, frustrated Lewis pairs, and transition‐metal catalysis.

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“…The smallest cone angle for the kinetic stabilization of [E( μ -NR)] 2 -type diradicaloids is about 200°. Typical examples of sterically demanding substituents − are Ter, Bbp, and Hyp, to name just three. The cone angle at a distance of 1.85 Å decreases along the series 232° (Ter) to 230° (Bbp) to 213° (Hyp) .…”

Section: Design Of Diradicals Synthesis Strategies and Preparative As...mentioning

confidence: 99%

Heteroatom-Based Diradical(oid)s

Hinz,

Bresien,

Breher

et al. 2023

Chem. Rev.

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Access to the most sterically crowded anilines via non-catalysed C–C coupling reactions

Abstract: The most sterically crowded anilines were prepared by non-catalyzed C–C coupling.

Cited by 7 publications

References 49 publications

Isolation of a Cu–H Monomer Enabled by Remote Steric Substitution of a N-Heterocyclic Carbene Ligand: Stoichiometric Insertion and Catalytic Hydroboration of Internal Alkenes

Isolation of a Cu–H Monomer Enabled by Remote Steric Substitution of a N-Heterocyclic Carbene Ligand: Stoichiometric Insertion and Catalytic Hydroboration of Internal Alkenes

Reactivity and Steric Parameters from 2D to 3D Bulky Pyridines: Increasing Steric Demand at Nitrogen with Chiral Azatriptycenes

Heteroatom-Based Diradical(oid)s

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