Transition-Metal-Catalyzed Electrophilic Amination: Application of O-Benzoylhydroxylamines in the Construction of the C-N Bond

Oxidative Syntheses of N,N-Dialkylhydroxylamines

Despite the wide utility of hydroxylamines in organic synthesis, relatively few are commercially available, and there is a need for direct, efficient, and selective methods for their synthesis. Herein, we report two complementary methods to accomplish direct oxidation of secondary amines using UHP as an oxidant. The first method uses 2,2,2-trifluoroethanol (TFE) and a large excess of amine. Isolation of hydroxylamine products is enabled by selective salt formation, and recovery of excess amine is demonstrated. The second method uses hexafluoroacetone as an additive and is highlighted by the 1:1 stoichiometry between the oxidant and amine.

Beyond Tertiary Amines: Introducing Secondary Amines by Palladium/Norbornene-Catalyzed Ortho Amination

Since the discovery of the palladium/norbornene (Pd/NBE)-catalyzed ortho amination in 2013, escaping the limitation of only yielding tertiary anilines has been a long-standing challenge. Here, we describe that, by carefully choosing the phosphine ligand and NBE mediator, the installation of a N-mono-alkylamino group becomes feasible. The reaction tolerates a wide range of aryl iodide substrates and various N-mono-tertiary alkylamine-derived electrophiles. Both ipso alkenylation and alkynylation can be realized. The synthetic utility of this method is exemplified by the formation of primary amino group via selective deprotection and streamlined access to N-heterocycles. Preliminary success of installing a bulky N-secondary alkylamino group and a mechanistic understanding of the decomposition pathways of mono N-alkylamine electrophiles have been obtained.

Nickel-Catalyzed Electrophilic Amination of the Biphenylene C-C σ-Bond

A nickel-catalyzed three-component carboamination of the biphenylene C-C σ-bond has been developed. Arylboronates and hydroxylamine derivatives work as carbon nucleophiles and nitrogen electrophiles, respectively, and the corresponding difunctionalized ring-opening products are obtained in good yields. The arylboronate nucleophile can be replaced with B2pin2 (boron nucleophile) and H-Si(OMe)3 (hydride nucleophile), thus allowing for the aminoboration and hydroamination of the biphenylene C-C σ-bond under similar nickel catalysis.

Copper-catalysed electrophilic carboamination of terminal alkynes with benzyne looked at through the computational lens

A detailed computational mechanistic study of the copper-catalysed three-component-type electrophilic carboamination of terminal alkynes with benzyne and an archetypal O-benzoylhydroxylamine electrophile is presented. Probing various plausible pathways for relevant elementary steps and scrutinising performance degradation pathways, with the aid of a reliable computational protocol applied to a realistic catalyst model combined with kinetic analysis, identified the pathways preferably traversed in productive catalysis. It entails rapid alkynylcupration of in situ generated benzyne to deliver the arylcopper nucleophile that undergoes amination with the O-benzoylhydroxylamine electrophile to afford copper benzoate. Umpolung-enabled electrophilic amination favours a multistep SN2-type oxidative addition/N-C bond-forming reductive elimination sequence involving a short-lived formal {P^P}CuIII carboxylate amido aryl intermediate. SN2-type displacement of the benzoate leaving group at the arylcopper nucleophile, which represents the catalyst resting state, is predicted to be the turnover limiting step. Alkynolysis transforms copper benzoate back to catalytically competent alkynylcopper. The computational probe of a wider range of substrates reveals that only severely ring-strained C6-arynes, C6-cycloalkynes and electron-deficient cyclopropenes featuring a highly reactive C≡C linkage could replace benzyne. Moreover, strict control of stationary benzyne concentration is indispensable for electrophilic carboamination to ever become achievable.

Pd(II)-Catalyzed 1,2-Oxyarylation of Alkenes with O-Acylhydroxylamines as the Oxygen Source

O-Acylhydroxylamine has been widely employed as an electrophilic amination reagent in transition-metal-catalyzed C-N coupling reactions, but its use as an electrophilic oxygen source has not been disclosed. Here, we report a Pd-catalyzed 1,2-oxyarylation of alkenes with O-acylhydroxylamines as an oxidant and an oxygen source for the first time. With simple amide as the monodentate directing group, this method features a broad substrate scope, good functional group tolerance, and mild conditions.

SN2 Reaction at the Amide Nitrogen Center Enables Hydrazide Synthesis

Nucleophilic substitutions are fundamentally important transformations in synthetic organic chemistry. Despite the substantial advances in bimolecular nucleophilic substitutions (SN2) at saturated carbon centers, analogous SN2 reaction at the amide nitrogen atom remains extremely limited. Here we report an SN2 substitution method at the amide nitrogen atom with amine nucleophiles for nitrogen-nitrogen (N-N) bond formation that leads to a novel strategy toward biologically and medicinally important hydrazide derivatives. We found the use of sulfonate-leaving groups at the amide nitrogen atom played a pivotal role in the reaction. This new N-N coupling reaction allows the use of O-tosyl hydroxamates as electrophiles and readily available amines, including acyclic aliphatic amines and saturated N-heterocycles as nucleophiles. The reaction features mild conditions, broad substrate scope (>80 examples), excellent functional group tolerability, and scalability. The method is applicable to late-stage modification of various approved drug molecules, thus enabling complex hydrazide scaffold synthesis.

Copper-Mediated N-Trifluoromethylation of O-Benzoylhydroxylamines

The use of trifluoromethyl containing compounds is well established within medicinal chemistry, with a range of approved drugs containing C-CF3 and O-CF3 moieties. However, the utilisation of the N-CF3 functional group remains relatively unexplored. This may be attributed to the challenging synthesis of this unit, with many current methods employing harsh conditions or less accessible reagents. A robust methodology for the N-trifluoromethylation of secondary amines has been developed, which employs an umpolung strategy in the form of a copper-catalysed electrophilic amination. The method is operationally simple, uses mild, inexpensive reagents, and has been used to synthesise a range of novel, structurally complex N-CF3 containing compounds.

Nitrenium ions as new versatile reagents for electrophilic amination

Herein we report the utilization of N-heterocyclic nitrenium ions - easily prepared, bench-stable and non-oxidating nitrogen sources for the efficient electrophilic amination of aliphatic and aromatic organometallic nucleophiles, towards the facile and general preparation of primary amines. To this end, a plethora of abundant organolithium and organomagnesium reagents were combined with nitrenium salts to generate a variety of previously unexplored N-alkyl and N-aryl triazanes. Through the simple hydrogenolysis of these relatively stable triazanes, we have prepared a diverse scope of primary amines, including linear and branched aliphatic as well as (hetero)aromatic amines possessing various stereo-electronic substituents. Furthermore, we present the facile synthesis of valuable 15N-labelled primary amines from easily prepared 15N-labelled nitrenium salts, as well as a one-pot approach to biologically relevant primary amines. Finally, a recyclable variant of the nitrenium precursor was prepared and a simple recovery protocol was developed to improve the atom-economy of this procedure.

Synthesis of Indoles Using the Electrophilic Potential of Diazirines

The electrophilic potential of diazirines has been utilized to obtain N-substituted diaziridines that are directly hydrolyzed to produce monosubstituted hydrazines. The hydrazines can undergo the Fisher process with enolizable carbonyls to yield multiple indole derivatives in moderate to high yields. The N-metalated diaziridine intermediates can undergo isomerization prior to electrophilic substitution, to form N,N-disubstituted hydrazones. The latter react with enolizable carbonyls to produce N-protected indole derivatives in a single step. This protocol was used to efficiently synthesize indomethacin, an anti-inflammatory drug.

Ortho-C-H methoxylation of aryl halides enabled by a polarity-reversed N-O reagent

Oxygen-substituted arenes widely exist in biologically important molecules and can serve as versatile handles to install other functional groups. However, direct and site-selective installation of oxygen groups to common aromatic compounds remains challenging, especially when additional arene functionalization is simultaneously required. Current arene C-H oxidation strategies generally require directing groups or precisely prefunctionalized substrates to control site-selectivity. While palladium/norbornene cooperative catalysis is promising for site-specific arene vicinal difunctionalization through simultaneous reactions with an electrophile and a nucleophile, the electrophile scope has been limited to species based on relatively 'soft' elements, such as carbon, nitrogen and sulfur. Here we report the development of an ortho oxygenation reaction with common aryl halides to rapidly deliver diverse aryl ethers. The coupling of the 'hard' oxygen electrophile is enabled by a stable, polarity-reversed, conformationally predistorted N-O reagent and facilitated by a C7-bromo-substituted norbornene mediator. Mechanistic studies reveal a unique SN2-type pathway between the N-O reagent as the oxygen electrophile and an electron-rich Pd(II) nucleophile.

Directing-Group-Free Arene C(sp2)-H Amination Using Bulky Aminium Radicals and DFT Analysis of Regioselectivity

A hydroxylamine-derived electrophilic aminating reagent produces a transient and bulky aminium radical intermediate upon in situ activation by either TMSOTf or TFA and a subsequent electron transfer from an iron(II) catalyst. Density functional theory calculations were used to examine the regioselectivity of arene C-H amination reactions on diversely substituted arenes. The calculations suggest a simple charge-controlled regioselectivity model that enables prediction of the major C(sp2)-H amination product.

Nickel-Catalyzed Amination of Alkyl Electrophiles

Bimolecular nucleophilic substitution SN2 is the earliest and most important means of amination of alkyl electrophiles; its practical utilization is largely limited to primary or activated substrates. Furthermore, a persistent challenge lies in establishing C(sp3)-N bonds from alkyl substrates in cross-coupling chemistry using palladium and nickel catalysts. Therefore, the methods of constructing C(sp3)-N bonds remain rare from alkyl electrophiles. The existing routes are limited to copper catalysis and photoredox catalysis. Here, we demonstrate an alternative amination strategy for rapid construction of C(sp3)-N bonds from accessible alkyl electrophiles, which were used as radical precursors under nickel catalysis by Ni (III) species reductive eliminations in high efficiency.

Synthesis of α-Aminophosphonates by Umpolung-Enabled Cu-Catalyzed Regioselective Hydroamination

A copper-catalyzed regioselective hydroamination of α,β-unsaturated phosphonates has been developed to form corresponding α-aminophosphonates of interest in medicinal chemistry. The introduction of an umpolung, electrophilic amination strategy with the hydroxylamine derivative is the key to achieving the α-amination regioselectivity, which is otherwise difficult under the conventional nucleophilic hydroamination conditions with the parent amine. Asymmetric synthesis with a chiral bisphosphine ligand and application to a related silylamination reaction are also described.

anti-Selective synthesis of β-boryl-α-amino acid derivatives by Cu-catalysed borylamination of α,β-unsaturated esters

A copper-catalysed regio- and diastereoselective borylamination of α,β-unsaturated esters with B₂pin₂ and hydroxylamines has been developed to deliver acyclic β-boryl-α-amino acid derivatives with high anti-diastereoselectivity (up to >99 : 1), which is difficult to obtain by the established methods. A chiral phosphoramidite ligand also successfully induces the enantioselectivity, giving the optically active β-borylated α-amino acids. The products can be stereospecifically transformed into β-functionalised α-amino acids, which are of potent interest in medicinal chemistry.

Traceless Benzylic C-H Amination via Bifunctional N-Aminopyridinium Intermediates

C-H amination reactions provide the opportunity to streamline the synthesis of nitrogen-containing organic small molecules. The impact of intermolecular C-H amination methods, however, is currently limited the frequent requirement for the amine precursors to bear activating groups, such as N-sulfonyl substituents, that are both challenging to remove and not useful synthetic handles for subsequent derivatization. Here, we introduce traceless nitrogen activation for C-H amination-which enables application of selective C-H amination chemistry to the preparation of diverse N-functionalized products-via sequential benzylic C-H N-aminopyridylation followed by Ni-catalyzed C-N cross-coupling with aryl boronic acids. Unlike many C-H amination reactions that provide access to protected amines, the current method installs an easily diversifiable synthetic handle that serves as a lynchpin for C-H amination, deaminative N-N functionalization sequences.

Copper-Catalyzed Stereospecific Transformations of Alkylboronic Esters

Copper-catalyzed stereospecific cross-couplings of boronic esters are reported. Boron "ate" complexes derived from pinacol boronic esters and tert-butyl lithium undergo stereospecific transmetalation to copper cyanide, followed by coupling with alkynyl bromides, allyl halides, propargylic halides, β-haloenones, hydroxylamine esters, and acyl chlorides. Through this simple transformation, commercially available inexpensive compounds can be employed to convert primary and secondary alkylboronic esters to a wide array of synthetically useful compounds.

Photoinduced Transition-Metal-Free Chan-Evans-Lam-Type Coupling: Dual Photoexcitation Mode with Halide Anion Effect

Herein, we report a photoinduced transition-metal-free C(aryl)-N bond formation between 2,4,6-tri(aryl)boroxines or arylboronic acids as an aryl source and 1,4,2-dioxazol-5-ones (dioxazolones) as an amide coupling partner. Chloride anion, either generated in situ by photodissociation of chlorinated solvent molecules or added separately as an additive, was found to play a critical cooperative role, thereby giving convenient access to a wide range of synthetically versatile N-arylamides under mild photo conditions. The synthetic virtue of this transition-metal-free Chan-Evans-Lam-type coupling was demonstrated by large-scale reactions, synthesis of 15N-labeled arylamides, and applicability toward biologically relevant compounds. On the basis of mechanistic investigations, two distinctive photoexcitations are proposed to function in the current process, in which the first excitation involving chloro-boron adduct facilitates the transition-metal-free activation of dioxazolones by single electron transfer (SET), and the second one enables the otherwise-inoperative 1,2-aryl migration of the thus-formed N-chloroamido-borate adduct.

Copper(I)-Catalyzed Asymmetric Synthesis of P-Chiral Aminophosphinites

Herein, a copper(I)-catalyzed reaction of diarylphosphines and O-benzoyl hydroxylamines is developed. In the cases of symmetrical diarylphosphines, a series of aminophosphinites is prepared in high yields. In the cases of unsymmetrical diarylphosphines, an array of P-chiral aminophosphinites is synthesized in high yields with high enantioselectivity by using a copper(I)-(R,R_P )-Ph-FOXAP complex as a chiral catalyst. Based on several control experiments and ³¹ P NMR studies, a two-electron redox mechanism involving the dynamic kinetic asymmetric transformation of unsymmetrical diarylphosphines is proposed for the copper(I)-catalyzed asymmetric reaction. Finally, one representative P-chiral phosphoric amide generated through the oxidation with H₂ O₂ is transformed to a chiral diarylphosphinate in high yield with retained enantioselectivity, which allows further transformations towards various P-chiral tertiary phosphines.

Hydroamination, Aminoboration, and Carboamination with Electrophilic Amination Reagents: Umpolung-Enabled Regio- and Stereoselective Synthesis of N-Containing Molecules from Alkenes and Alkynes

Nitrogen (N) is ubiquitously found in bioactive molecules, pharmaceutical agents, and organic functional materials. Accordingly, development of new C-N bond-forming catalysis has been one of the long-standing research subjects in synthetic organic chemistry. In this Perspective, recent advances in highly selective amination reactions with electrophilic amination reagents are described: by taking advantage of the concept of nitrogen umpolung, otherwise challenging aminofunctionalizations, such as hydroamination, aminoboration, and carboamination, of readily available feedstock-like alkenes and alkynes are possible, giving densely functionalized complex and often chiral alkylamines with high selectivity. The scope, limitations, and reaction mechanism are briefly summarized.

Rh(III)-Catalysed Cascade C-H Imidization/Cyclization of N-Methoxybenzamides with Isoxazolones for the Assembly of Dihydroquinazolin-4(1H)-one Derivatives

By virtue of isoxazolones as viable imidizating reagents, an efficient Rh(III)-catalysed redox-neutral C-H imidization/cyclization cascade has been developed for the specific assembly of dihydroquinazolin-4(1H)-ones with the equipment of a quaternary...

Directing group switch in copper-catalyzed electrophilic C–H amination/migratory annulation cascade: divergent access to benzimidazolone/benzimidazole

We present here a copper-catalyzed electrophilic ortho C–H amination of protected naphthylamines with N-(benzoyloxy)amines, cyclization with the pendant amide, and carbon to nitrogen 1,2-directing group migration cascade to access N,N-disubstituted 2-benzimidazolinones. Remarkably, this highly atom-economic tandem reaction proceeds through a C–H and C–C bond cleavage and three new C–N bond formations in a single operation. Intriguingly, the reaction cascade was altered by the subtle tuning of the directing group from picolinamide to thiopicolinamide furnishing 2-heteroaryl-imidazoles via the extrusion of hydrogen sulfide. This strategy provided a series of benzimidazolones and benzimidazoles in moderate to high yields with low catalyst loading (66 substrates with yields up to 99%). From the control experiments, it was observed that after the C–H amination an incipient tetrahedral oxyanion or thiolate intermediate is formed via an intramolecular attack of the primary amine to the amide/thioamide carbonyl. It undergoes either a 1,2-pyridyl shift with the retention of the carbonyl moiety or H₂S elimination for scaffold diversification. Remarkably, inspite of a positive influence of copper in the reaction outcome, from our preliminary investigations, the benzimidazolone product was obtained in good to moderate yields in two steps under metal-free conditions. The N-pyridyl moiety of the benzimidazolone was removed for further manipulation of the free NH group.

A novel directing group switch strategy is explored in a copper-catalyzed divergent synthesis of benzimidazolone via electrophilic C–H amination/cyclization/1,2-C → N directing group migration cascade and benzimidazole through the extrusion of H₂S.

Recent Advances in Copper-Catalyzed C-N Bond Formation Involving N-Centered Radicals

C-N bonds are pervasive throughout organic-based materials, natural products, pharmaceutical compounds, and agricultural chemicals. Considering the widespread importance of C-N bonds, the development of greener and more convenient ways to form C-N bonds, especially in late-stage synthesis, has become one of the hottest research goals in synthetic chemistry. Copper-catalyzed radical reactions involving N-centered radicals have emerged as a sustainable and promising approach to build C-N bonds. As a chemically popular and diverse radical species, N-centered radicals have been used for all kinds of reactions for C-N bond formation by taking advantage of their inherently incredible reactive flexibility. Copper is also the most abundant and economic catalyst with the most relevant activity for facilitating the synthesis of valuable compounds. Therefore, the aim of the present Review was to illustrate recent and significant advances in C-N bond formation methods and to understand the unique advantages of copper catalysis in the generation of N-centered radicals since 2016. To provide an ease of understanding for the readers, this Review was organized based on the types of nitrogen sources (amines, amides, sulfonamides, oximes, hydrazones, azides, and tert-butyl nitrite).

A Cu-Promoted C-N Coupling of Boron Esters and Diaziridinone: An Approach to Aryl Ureas

A novel Cu-promoted C-N coupling between boron esters and di-tert-butyldiaziridinone is described. A wide variety of aryl ureas can be readily obtained under mild conditions with up to a 92% yield.

Exploiting Iminoquinones as Electrophilic at Nitrogen "N+" Synthons for C-N Bond Construction

New methods for C-N bond construction exploiting the N-centered electrophilic character of iminoquinones are reported. Iminoquinones, generated in situ via the condensation of o-vinylanilines with benzoquinones, undergo acid-catalyzed cyclization to afford N-arylindoles in excellent yields. Under similar reaction conditions, homoallylic amines react analogously to afford N-arylpyrroles. Additionally, organometallic nucleophiles are shown to add to the nitrogen atom of N-alkyliminoquinones to provide amine products. Finally, iminoquinones are shown to be competent electrophiles for copper-catalyzed hydroamination.

An umpolung-enabled copper-catalysed regioselective hydroamination approach to α-amino acids

A copper-catalysed regio- and stereoselective hydroamination of acrylates with hydrosilanes and hydroxylamines has been developed to afford the corresponding α-amino acids in good yields. The key to regioselectivity control is the use of hydroxylamine as an umpolung, electrophilic amination reagent. Additionally, a judicious choice of conditions involving the CsOPiv base and DTBM-dppbz ligand of remote steric hindrance enables the otherwise challenging C-N bond formation at the α position to the carbonyl. The point chirality at the β-position is successfully controlled by the Xyl-BINAP or DTBM-SEGPHOS chiral ligand with similarly remote steric bulkiness. The combination with the chiral auxiliary, (-)-8-phenylmenthol, also induces stereoselectivity at the α-position to form the optically active unnatural α-amino acids with two adjacent stereocentres.

Copper-Catalyzed Intermolecular C(sp2)-H Amination with Electrophilic O-Benzoyl Hydroxylamines

A copper-catalyzed intermolecular electrophilic amination of benzamides with O-benzoyl hydroxylamines was achieved with the assistance of an 8-aminoquinolyl group. With this protocol, good compatibility was observed for a variety of aryl amides and heteroaryl amides, and excellent tolerance with various functional groups was achieved. Significantly, the monoaminated product was overwhelmingly delivered under the simple reaction conditions. Preliminary mechanistic investigations suggested that a radical pathway should be excluded and C-H activation be potentially the rate-determining step.

External-oxidant-free amino-benzoyloxylation of unactivated alkenes of unsaturated ketoximes with O-benzoylhydroxylamines

A new copper-catalyzed two-component amino-benzoyloxylation of unactivated alkenes of unsaturated ketoximes with O-benzoylhydroxylamines as the benzoyloxy sources is developed. Chemoselectivity of this method toward amino-benzoyloxylation or oxy-benzoyloxylation of alkenyl ketoximes relies on the position of the tethered olefins, and provides an external-oxidant-free alkene difunctionalization route that directly utilizes O-benzoylhydroxylamines as the benzoyloxy radical precursors and internal oxidants for the divergent synthesis of cyclic nitrones and isoxazolines.

Asymmetric copper-catalyzed propargylic amination with amine hydrochloride salts

The highly enantioselective copper-catalyzed propargylic amination of propargylic esters with amine hydrochloride salts has been realized for the first time using copper salts with chiral N,N,P-ligands. This method features a broad substrate scope and wide functional group tolerance, generating propargylic amines in good to excellent yields with high enantioselectivities (up to 99% ee). The utility of the approach was demonstrated by late-stage functionalization of marketed pharmaceuticals.

Electrophilic Aminating Agents in Total Synthesis

Classical amination methods involve the reaction of a nitrogen nucleophile with an electrophilic carbon center; however, in recent years, umpoled strategies have gained traction where the nitrogen source acts as an electrophile. A wide range of electrophilic aminating agents are now available, and these underpin a range of powerful C−N bond‐forming processes. In this Review, we highlight the strategic use of electrophilic aminating agents in total synthesis.

Nucleophilic Aromatic Substitution of Polyfluoroarene to Access Highly Functionalized 10-Phenylphenothiazine Derivatives

Nucleophilic aromatic substitution (S_NAr) reactions can provide metal-free access to synthesize monosubstituted aromatic compounds. We developed efficient S_NAr conditions for p-selective substitution of polyfluoroarenes with phenothiazine in the presence of a mild base to afford the corresponding 10-phenylphenothiazine (PTH) derivatives. The resulting polyfluoroarene-bearing PTH derivatives were subjected to a second S_NAr reaction to generate highly functionalized PTH derivatives with potential applicability as photocatalysts for the reduction of carbon–halogen bonds.

N-Nosyl-O-bromoethyl hydroxylamine acts as a multifunctional formaldehyde, formaldimine, and 1,2-oxazetidine surrogate for C–C and C–O bond-forming reactions

Hydroxylamine could chemo- and stereoselectively produce α-hydroxymethyl and α-aminomethyl ketones and chiral α-alkoxyl and α-aminomethyl carboxylates in good yields.

Copper-Catalyzed Electrophilic Amination of Arylboronic Acids with Anthranils: An Access to N-Aryl-2-aminophenones

An efficient copper-catalyzed electrophilic amination strategy has been established for the rapid synthesis of N-aryl-2-aminophenones from readily available arylboronic acids/esters and anthranils. This protocol features good functional group tolerance, broad substrate scope, and operational simplicity. Moreover, a tandem C-H borylation and C-N coupling protocol has also been developed to transform simple arenes to the valuable N-aryl-2-aminophenones in one pot. Additionally, the synthetic potential of this methodology is further demonstrated by the synthesis of various useful N-heterocycles and derivatives.

Copper-Catalyzed Electrophilic Etherification of Arylboronic Esters with Isoxazolidines

A copper-catalyzed electrophilic etherification of arylboronic esters is reported. Isoxazolidines are utilized as easily available and stable [RO]⁺ surrogates to give 1,3-amino aryl ethers. The O-selective arylation of isoxazolidines takes place without causing competitive N-arylation. In contrast to previously reported anionic conditions, our copper-catalyzed conditions are mild enough to achieve high functional group tolerance. Preliminary mechanistic studies and DFT calculations support that the reaction proceeds via a transmetalation/oxidative addition pathway, followed by a Lewis acid-promoted reductive elimination to induce the crucial O-selectivity.

Preparation of Tertiary Amines from Tris(2-cyanoethyl)amine Using Three Successive Cobalt-Catalyzed Electrophilic Aminations with Organozinc Halides

We report a stepwise preparation of triple alkylated or arylated tertiary amines, starting from commercially available tris(2-cyanoethyl)amine using three successive reaction sequences involving a selective oxidation (formation of an N-oxide followed by a Cope elimination) leading to an intermediate hydroxylamine, a benzoylation, and a cobalt-catalyzed electrophilic amination with organozinc halides.