Copper-Catalyzed Electrophilic Amination of Organoaluminum Nucleophiles with O-Benzoyl Hydroxylamines

Cross-Coupling of Heteroatomic Electrophiles

At the advent of cross-coupling chemistry, carbon electrophiles based on halides or pseudohalides were the only suitable electrophilic coupling partners. Almost two decades passed before the first cross-coupling reaction of heteroatom-based electrophiles was reported. Early work by Murai and Tanaka initiated investigations into silicon electrophiles. Narasaka and Johnson pioneered the way in the use of nitrogen electrophiles, while Suginome began the exploration of boron electrophiles. The chemistry reviewed within provides perspective on the use of heteroatomic electrophiles, specifically silicon-, nitrogen-, boron-, oxygen-, and phosphorus-based electrophiles in transition-metal catalyzed cross-coupling. For the purposes of this review, a loose definition of cross-coupling is utilized; all reactions minimally proceed via an oxidative addition event. Although not cross-coupling in a traditional sense, we have also included catalyzed reactions that join a heteroatomic electrophile with an in situ generated nucleophile. However, for brevity, those involving hydroamination or C-H activation as a key step are largely excluded. This work includes primary references published up to and including October 2018.

Cobalt-Catalyzed Electrophilic Aminations with Anthranils: An Expedient Route to Condensed Quinolines

The reaction of various organozinc pivalates with anthranils provides anilines derivatives, which cyclize under acidic conditions providing condensed quinolines. Using alkenylzinc pivalates, electron-rich arylzinc pivalates or heterocyclic zinc pivalates produces directly the condensed quinolines of which several structures belong to new heterocyclic scaffolds. These N-heterocycles are of particular interest for organic light emitting diodes with their high photoluminescence quantum yields and long exciton lifetimes as well as for hole-transporting materials in methylammonium lead iodide perovskites solar cells due to an optimal band alignment for holes and a large bandgap.

A Modified System for the Synthesis of Enantioenriched N-Arylamines through Copper-Catalyzed Hydroamination

Despite significant recent progress in copper-catalyzed enantioselective hydroamination chemistry, the synthesis of chiral N-arylamines, which are frequently found in natural products and pharmaceuticals, has not been realized. Initial experiments with N-arylhydroxylamine ester electrophiles were unsuccessful and, instead, their reduction in the presence of copper hydride (CuH) catalysts was observed. Herein, we report key modifications to our previously reported hydroamination methods that lead to broadly applicable conditions for the enantioselective net addition of secondary anilines across the double bond of styrenes, 1,1-disubstituted olefins, and terminal alkenes. NMR studies suggest that suppression of the undesired reduction pathway is the basis for the dramatic improvements in yield under the reported method.

Cp2TiCl2-catalyzed highly regioselective hydroamination of styrenes with hydroxylamines

An efficient Cp₂TiCl₂-catalyzed one-pot two-step hydroamination procedure that allows the direct formation of tertiary amines from styrenes and an electrophilic nitrogen source has been reported with high regioselectivity.

Metal free direct C(sp2)–H arylaminations using nitrosoarenes to 2-hydroxy-di(het)aryl amines as multifunctional Aβ-aggregation modulators

A direct C(sp²)–H arylamination of 2-hydroxyarenes using nitrosoarenes was achieved under metal free conditions without the aid of additional reagents/steps for N–O bond cleavage.

Non-Deprotonative Primary and Secondary Amination of (Hetero)Arylmetals

Herein we disclose a novel method for the facile transfer of primary (-NH2) and secondary amino groups (-NHR) to heteroaryl- as well as arylcuprates at low temperature without the need for precious metal catalysts, ligands, excess reagents, protecting and/or directing groups. This one-pot transformation allows unprecedented functional group tolerance and it is well-suited for the amination of electron-rich, electron-deficient as well as structurally complex (hetero)arylmetals. In some of the cases, only catalytic amounts of a copper(I) salt is required.

Emerging Developments Using Nitrogen-Heteroatom Bonds as Amination Reagents in the Synthesis of Aminoarenes

Aminoarenes constitute valuable building blocks in organic synthesis and an essential skeleton ubiquitously found in ligands, agrochemicals, and pharmaceuticals. This Synopsis presents recent amination methods using nitrogen-heteroatom bonds as a powerful and versatile platform to rapidly synthesize diverse aminoarenes, with a focus on aryne amino functionalization and transition-metal-catalyzed arene C-H amination.

Cu-Catalyzed electrophilic amination of internal alkynes via hydroalumination

A straightforward and efficient method for the synthesis of 1,2-diaryl-substituted enamines through the Cu-catalyzed electrophilic amination reaction of O-benzoyl hydroxylamines with vinylaluminum reagents generated in situ from the Ni-catalyzed hydroalumination of readily accessible internal aryl acetylenes is described.

Metal-Free Direct Amidation of Naphthoquinones Using Hydroxamic Acids as an Amide Source: Application in the Synthesis of an HDAC6 Inhibitor

A novel synthetic approach to amidoquinones by the reaction of naphthoquinones with hydroxamic acids under basic conditions was developed. The reaction is mild and operationally simple, and it affords high yields of amidoquinones. With this new method, a novel, very strong HDAC6 inhibitor, which showed high toxicity to AML cells, was successfully synthesized.

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

Transition-metal-catalyzed electrophilic amination has been developed into a powerful tool for C-N bond construction. So far, O-benzoylhydroxylamines are the most widely used electrophilic aminating reagents. Herein, we summarize the recent advances of O-benzoylhydroxylamines involved in electrophilic amination catalyzed by transition metals. Several pioneering studies and some of the relevant mechanisms are discussed in this review.

Cp*Rh(iii)-catalyzed electrophilic amination of arylboronic acids with azo compounds for synthesis of arylhydrazides

A [Cp*Rh(iii)]-catalyzed electrophilic amination of arylboronic acids with azocarboxylates for the synthesis of mono- and di-arylhydrazides was developed.

Copper-Catalyzed Electrophilic Amination of Heteroarenes via C-H Alumination

A highly efficient Cu-catalyzed electrophilic amination reaction of readily available heteroarenes with O-benzoyl hydroxylamines via a one-pot C-H alumination is reported. The reactions were catalyzed using 1 mol % of CuCl to afford various heteroaryl amines in good to excellent yields. The direct C-H lithiation/transalumination of heteroarenes and catalytic amination sequence can be performed in a single vessel on gram scales.

Asymmetric Addition of Pyridyl Aluminum Reagents to Aldehydes Catalyzed by a Titanium(IV) Catalytic System of (R)-H8-BINOLate

The asymmetric addition of pyridyl aluminum reagents to aldehydes has been successfully developed by employing a titanium(IV) catalytic system of (R)-H8-BINOLate, which affords a series of valuable optically active diarylmethanols containing various pyridyl groups in high yields with excellent enantioselectivities of up to 98% ee.