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Chiral amines are commonly used in the pharmaceutical and agrochemical industries 1 . The strong demand for unnatural chiral amines has driven the development of catalytic asymmetric methods 1,2 . Although the N-alkylation of aliphatic amines with alkyl halides has been widely adopted for over 100 years, catalyst poisoning and unfettered reactivity have been preventing the development of a catalyst-controlled enantioselective version 3-5 . Here we report the use of chiral tridentate anionic ligands to enable the copper-catalysed chemoselective and enantioconvergent N-alkylation of aliphatic amines with α-carbonyl alkyl chlorides. This method can directly convert feedstock chemicals, including ammonia and pharmaceutically relevant amines, into unnatural chiral α-amino amides under mild and robust conditions. Excellent enantioselectivity and functional-group tolerance were observed. The power of the method is demonstrated in a number of complex settings, including late-stage functionalization and in the expedited synthesis of diverse amine drug molecules. The current method indicates that multidentate anionic ligands are a general solution for overcoming transition-metal-catalyst poisoning., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

The copper-catalyzed enantioselective intermolecular radical 1,2-carboamination of alkenes with readily accessible alkyl halides is an appealing strategy for producing chiral amine scaffolds. The challenge arises from the easily occurring atom transfer radical addition between alkyl halides and alkenes and the issue of enantiocontrol. We herein describe a radical alkene 1,2-carboamination with sulfoximines in a highly chemo- and enantioselective manner. The key to the success of this process is the conceptual design of a counterion/highly sterically demanded ligand coeffect to promote the ligand exchange of copper(I) with sulfoximines and forge chiral C-N bonds between alkyl radicals and the chiral copper(II) complex. The reaction covers alkenes bearing distinct electronic properties, such as aryl-, heteroaryl-, carbonyl-, and aminocarbonyl-substituted ones, and various radical precursors, including alkyl chlorides, bromides, iodides, and the CF 3 source. Facile transformations deliver many chiral amine building blocks of interest in organic synthesis and related areas.

The enantioconvergent cross-coupling of racemic alkyl halides represents a powerful tool for the synthesis of enantioenriched molecules. In this regard, the first-row transition metal catalysis provides a suitable mechanism for stereoconvergence by converting racemic alkyl halides to prochiral radical intermediates owing to their good single-electron transfer ability. In contrast to the noble development of chiral nickel catalyst, copper-catalyzed enantioconvergent radical cross-coupling of alkyl halides is less studied. Besides the enantiocontrol issue, the major challenge arises from the weak reducing capability of copper that slows the reaction initiation. Recently, significant efforts have been dedicated to basic research aimed at developing chiral ligands for copper-catalyzed enantioconvergent radical cross-coupling of racemic alkyl halides. This perspective will discuss the advances in this burgeoning area with particular emphasis on the strategic chiral anionic ligand design to tune the reducing capability of copper for the reaction initiation under thermal conditions from our research group.

In contrast with the well-established enantioconvergent radical C(sp 3 )-C cross-coupling of racemic secondary alkyl electrophiles, the corresponding coupling of tertiary electrophiles to forge all-carbon quaternary stereocentres remains underexplored. The major challenge arises from the steric hindrance and the difficult enantio-differentiation of three distinct carbon substituents of prochiral tertiary radicals. Here we demonstrate a general copper-catalysed enantioconvergent C(sp 3 )-C(sp) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes (87 examples). Key to the success is the rational design of chiral anionic N,N,N-ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway. This protocol provides a practical platform for the construction of chiral C(sp 3 )-C(sp/sp 2 /sp 3 ) bonds, allowing for expedient access to an array of synthetically challenging quaternary carbon building blocks of interest in organic synthesis and related areas., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

The enantioconvergent radical C(sp 3 )-C(sp 2 ) cross-coupling of alkyl halides with alkenylboronate esters is an appealing tool in the assembly of synthetically valuable enantioenriched alkenes owing to the ready availability, low toxicity, and air/moisture stability of alkenylboronate esters. Here, we report a copper/chiral N,N,N-ligand catalytic system for the enantioconvergent cross-coupling of benzyl/propargyl halides with alkenylboronate esters (>80 examples) with good functional group tolerance. The key to the success is the rational design of hemilabile N,N,N-ligands by mounting steric hindrance at the ortho position of one coordinating quinoline ring. Thus, the newly designed ligand could not only promote the radical cross-coupling process in the tridentate form but also deliver enantiocontrol over highly reactive alkyl radicals in the bidentate form. Facile follow-up transformations highlight its potential utility in the synthesis of various enantioenriched building blocks as well as in the late-stage functionalization for drug discovery.

A copper-catalyzed highly anti -selective radical 1,2-alkylarylation of terminal alkynes with aryl boronic acids and alkyl bromides has been established. The reaction exhibits high compatibility with a wide range of terminal alkynes and diverse aryl boronic acids, thus providing facile access to various stereodefined trisubstituted alkenes in high yield under mild reaction conditions. Preliminary mechanistic investigations support the formation of alkyl radicals and their subsequent addition to alkynes in the reaction.

In contrast with the well‐established C(sp2)−SCF3 cross‐coupling to forge the Ar−SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3)−SCF3 bond has remained largely unexplored. We herein disclose a copper‐catalyzed enantioselective radical C(sp3)−SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino‐oxazoline‐derived anionic N,N,P‐ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3)−SCF3 cross‐coupling of racemic benzyl halides and three‐component 1,2‐carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3‐containing molecules of interest in organic synthesis and medicinal chemistry. [ABSTRACT FROM AUTHOR]

In contrast with the well‐established C(sp2)−SCF3 cross‐coupling to forge the Ar−SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3)−SCF3 bond has remained largely unexplored. We herein disclose a copper‐catalyzed enantioselective radical C(sp3)−SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino‐oxazoline‐derived anionic N,N,P‐ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3)−SCF3 cross‐coupling of racemic benzyl halides and three‐component 1,2‐carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3‐containing molecules of interest in organic synthesis and medicinal chemistry. [ABSTRACT FROM AUTHOR]

The enantioconvergent radical Suzuki–Miyaura cross-coupling of racemic alkyl halides represents a powerful approach for the construction of valuable C(sp3)–C bonds. In this regard, the earth-abundant first-row transition metal (Ni, Fe, Co, and Cu) catalyst possesses a good single-electron transfer ability and can easily convert racemic alkyl halides to the prochiral alkyl radicals, providing an ideal solution for enantioconvergence. The utilization of chiral ligands would further facilitate the realization of enantioselective control over the prochiral alkyl radicals. This Perspective will discuss the advances and anticipate further development in this burgeoning field. [ABSTRACT FROM AUTHOR]

Transition‐metal catalyzed enantioconvergent cross‐coupling of tertiary alkyl halides with ammonia offers a rapid avenue to chiral unnatural α,α‐disubstituted amino acids. However, the construction of chiral C−N bonds between tertiary‐carbon electrophiles and nitrogen nucleophiles presented a great challenge owing to steric congestion. We report a copper‐catalyzed enantioconvergent radical C−N cross‐coupling of alkyl halides with sulfoximines (as ammonia surrogates) under mild conditions by employing a chiral anionic N,N,N‐ligand with a long spreading side arm. An array of α,α‐disubstituted amino acid derivatives were obtained with good efficiency and enantioselectivity. The synthetic utility of the strategy has been showcased by the elaboration of the coupling products into different chiral α‐fully substituted amine building blocks. [ABSTRACT FROM AUTHOR]

Herein, we describe a Cu(I)/phosphoric acid catalyzed intramolecular radical tertiary C(sp3)−H amination of N‐chlorosulfonamide, providing an applicable route to the pyrrolidine structural motifs bearing an α‐quaternary stereocenter (>20 examples with up to 94 % yield). Mechanistic studies indicate that the reaction involves an intramolecular 1,5‐hydrogen atom transfer process to form the key tertiary C‐centered radical followed by a C−N bond formation. The corresponding enantioselective amination is accordingly disclosed by Cu(I)/chiral phosphoric acid catalyst to afford the chiral products with up to 81 % enantiomeric excess (ee). This strategy is anticipated to facilitate the development of tertiary C(sp3)−H functionalization. [ABSTRACT FROM AUTHOR]

The copper‐catalyzed enantioselective radical difunctionalization of alkenes from readily available alkyl halides and organophosphorus reagents possessing a P−H bond provides an appealing approach for the synthesis of α‐chiral alkyl phosphorus compounds. The major challenge arises from the easy generation of a P‐centered radical from the P−H‐type reagent and its facile addition to the terminal side of alkenes, leading to reverse chemoselectivity. We herein disclose a radical 1,2‐carbophosphonylation of styrenes in a highly chemo‐ and enantioselective manner. The key to the success lies in not only the implementation of dialkyl phosphites with a strong bond dissociation energy to promote the desired chemoselectivity but also the utilization of an anionic chiral N,N,N‐ligand to forge the chiral C(sp3)−P bond. The developed Cu/N,N,N‐ligand catalyst has enriched our library of single‐electron transfer catalysts in the enantioselective radical transformations. [ABSTRACT FROM AUTHOR]

The copper‐catalyzed enantioconvergent radical C(sp3)−C(sp2) cross‐coupling of tertiary α‐bromo‐β‐lactams with organoboronate esters could provide the synthetically valuable α‐quaternary β‐lactams. The challenge arises mainly from the construction of sterically congested quaternary stereocenters between the tertiary alkyl radicals and chiral copper(II) species. Herein, we describe our success in achieving such transformations through the utilization of a copper/hemilabile N,N,N‐ligand catalyst to forge the sterically congested chiral C(sp3)−C(sp2) bond via a single‐electron reduction/transmetalation/bond formation catalytic cycle. The synthetic potential of this approach is shown in the straightforward conversion of the corresponding products into many valuable building blocks. We hope that the developed catalytic cycle would open up new vistas for more enantioconvergent cross‐coupling reactions. [ABSTRACT FROM AUTHOR]

Catalytic enantioselective hydroxylation of prochiral dihydrosilanes with water is expected to be a highly efficient way to access Si‐chiral silanols, yet has remained unknown up to date. Herein, we describe a strategy for realizing this reaction: using an alkyl bromide as a single‐electron transfer (SET) oxidant for invoking CuII species and chiral multidentate anionic N,N,P‐ligands for effective enantiocontrol. The reaction readily provides a broad range of Si‐chiral silanols with high enantioselectivity and excellent functional group compatibility. In addition, we manifest the synthetic potential by establishing two synthetic schemes for transforming the obtained products into Si‐chiral compounds with high structural diversity. Our preliminary mechanistic studies support a mechanism involving SET for recruiting chiral CuII species as the active catalyst and its subsequent σ‐metathesis with dihydrosilanes. [ABSTRACT FROM AUTHOR]

The intermolecular asymmetric radical oxidative C(sp3)−C(sp) cross‐coupling of C(sp3)−H bonds with readily available terminal alkynes is a promising method to forge chiral C(sp3)−C(sp) bonds because of the high atom and step economy, but remains underexplored. Here, we report a copper‐catalyzed asymmetric C(sp3)−C(sp) cross‐coupling of (hetero)benzylic and (cyclic)allylic C−H bonds with terminal alkynes that occurs with high to excellent enantioselectivity. Critical to the success is the rational design of chiral oxazoline‐derived N,N,P(O)‐ligands that not only tolerate the strong oxidative conditions which are requisite for intermolecular hydrogen atom abstraction (HAA) processes but also induce the challenging enantiocontrol. Direct access to a range of synthetically useful chiral benzylic alkynes and 1,4‐enynes, high site‐selectivity among similar C(sp3)−H bonds, and facile synthesis of enantioenriched medicinally relevant compounds make this approach very attractive. [ABSTRACT FROM AUTHOR]

In contrast to the wealth of asymmetric transformations for generating central chirality from alkyl radicals, the enantiocontrol over the allenyl radicals for forging axial chirality represents an uncharted domain. The challenge arises from the unique elongated linear configuration of the allenyl radicals that necessitates the stereo‐differentiation of remote motifs away from the radical reaction site. We herein describe a copper‐catalyzed asymmetric radical 1,4‐carboalkynylation of 1,3‐enynes via the coupling of allenyl radicals with terminal alkynes, providing diverse synthetically challenging tetrasubstituted chiral allenes. A chiral N,N,P‐ligand is crucial for both the reaction initiation and the enantiocontrol over the highly reactive allenyl radicals. The reaction features a broad substrate scope, covering a variety of (hetero)aryl and alkyl alkynes and 1,3‐enynes as well as radical precursors with excellent functional group tolerance. [ABSTRACT FROM AUTHOR]

The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)−H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)−H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzo[d]oxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)−H bond and the involvement of alkyl radical species under the reaction conditions. [ABSTRACT FROM AUTHOR]

We describe a photoinduced copper‐catalyzed asymmetric radical decarboxylative alkynylation of bench‐stable N‐hydroxyphthalimide(NHP)‐type esters of racemic alkyl carboxylic acids with terminal alkynes, which provides a flexible platform for the construction of chiral C(sp3)−C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo‐ and cross‐coupling catalyst but also tuning of the NHP‐type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP‐type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl‐, allyl‐, and aminocarbonyl‐substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method. [ABSTRACT FROM AUTHOR]

Radical‐involved enantioselective oxidative C−H bond functionalization by a hydrogen‐atom transfer (HAT) process has emerged as a promising method for accessing functionally diverse enantioenriched products, while asymmetric C(sp3)−H bond amination remains a formidable challenge. To address this problem, described herein is a dual CuI/chiral phosphoric acid (CPA) catalytic system for radical‐involved enantioselective intramolecular C(sp3)−H amination of not only allylic positions but also benzylic positions with broad substrate scope. The use of 4‐methoxy‐NHPI (NHPI=N‐hydroxyphthalimide) as a stable and chemoselective HAT mediator precursor is crucial for the fulfillment of this transformation. Preliminary mechanistic studies indicate that a crucial allylic or benzylic radical intermediate resulting from a HAT process is involved. [ABSTRACT FROM AUTHOR]

Abstract: A copper‐catalyzed asymmetric radical oxytrifluoromethylation of alkenyl oxime and Togni's reagent has been successfully developed, thereby providing straightforward access to CF3‐containing isoxazolines bearing α‐tertiary stereocenters with excellent yield and enantioselectivity. The key to success is the rational design of cinchona‐alkaloid‐based sulfonamides as neutral/anionic hybrid ligands to effectively control the stereochemistry in copper‐catalyzed reactions involving free alkyl radical species. The utility of this method is illustrated by efficient transformation of the products into useful chiral CF3‐containing 1,3‐aminoalcohols. [ABSTRACT FROM AUTHOR]

A conceptually novel strategy with achiral pyridine as the ancillary ligand to stabilize high-valent copper species for the first asymmetric radical oxytrifluoromethylation of alkenes with alcohols under CuI/phosphoric acid dual-catalysis has been developed. The transformation features mild reaction conditions, a remarkably broad substrate scope and excellent functional group tolerance, offering an efficient approach to a wide range of trifluoromethyl-substituted tetrahydrofurans bearing an α-tertiary stereocenter with excellent enantioselectivity. Mechanistic studies support the presumed role of the achiral pyridine as a coordinative ligand on copper metal to stabilize the key transient reaction species involved in the asymmetric induction process. [ABSTRACT FROM AUTHOR]

• Tuning the impedance matching characteristics by using copper particles and polypyrrole • Economical and wide bandwidth RA was prepared from magnetoelectric powders. • lightweight microwave absorber with just 20 wt.% filler loading. • Copper and PPY shell improve the RL upto -24 dB with 3 GHz bandwidth. • Practical microwave absorber was produced by polyurethane matrix using as paint. A new multifunctional microwave absorbing material is designed. Two types of ferrites were synthesized, namely soft NiCoTi ferrite and hard SrCoTi ferrites, by sol-gel auto combustion method. Then, the ferrites along with an appropriate quantity of micro-copper particles were coated by polypyrrole using in situ chemical polymerization of pyrrole. The resulted material was hosted into a polyurethane matrix to prepare a microwave absorbing paint. The accumulative roles of the different components of the microwave absorber were investigated. The permittivity and permeability were recorded in the X-band and the reflection loss of the material at different thicknesses was estimated. The structure of the prepared microwave absorbing material was investigated using XRD and FTIR spectroscopy. VSM was used to record the samples' magnetic hysteresis loops. The morphology of the absorber was studied using SEM. The new prepared microwave absorbing composite material was compared to a simple mixture of its components and the importance effect of the interfacial polarization was highlighted. The microwave absorption properties were measured in the X-band range as a function of absorber thickness, Ferrites/PPY ratio and copper percentage. By changing Ferrites/PPY ratio the microwave absorption performance was tuned. The optimal copper percentage in the composite was optimized and it was found that 10 %w/w of copper widens the -10 dB bandwidth to 3 GHz and enhances the maximum reflection loss to -24 dB. [ABSTRACT FROM AUTHOR]

In contrast with the well‐established C(sp2)−SCF3 cross‐coupling to forge the Ar−SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3)−SCF3 bond has remained largely unexplored. We herein disclose a copper‐catalyzed enantioselective radical C(sp3)−SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino‐oxazoline‐derived anionic N,N,P‐ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3)−SCF3 cross‐coupling of racemic benzyl halides and three‐component 1,2‐carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3‐containing molecules of interest in organic synthesis and medicinal chemistry. [ABSTRACT FROM AUTHOR]

In contrast with the well‐established C(sp2)−SCF3 cross‐coupling to forge the Ar−SCF3 bond, the corresponding enantioselective coupling of readily available alkyl electrophiles to forge chiral C(sp3)−SCF3 bond has remained largely unexplored. We herein disclose a copper‐catalyzed enantioselective radical C(sp3)−SCF3 coupling of a range of secondary/tertiary benzyl radicals with the easily available (Me4N)SCF3 reagent. The key to the success lies in the utilization of chiral phosphino‐oxazoline‐derived anionic N,N,P‐ligands through tuning electronic and steric effects for the simultaneous control of the reaction initiation and enantioselectivity. This strategy can successfully realize two types of asymmetric radical reactions, including enantioconvergent C(sp3)−SCF3 cross‐coupling of racemic benzyl halides and three‐component 1,2‐carbotrifluoromethylthiolation of arylated alkenes under mild reaction conditions. It therefore provides a highly flexible platform for the rapid assembly of an array of enantioenriched SCF3‐containing molecules of interest in organic synthesis and medicinal chemistry. [ABSTRACT FROM AUTHOR]

• Terminal alkynes are used in trifluoromethylalkynylation of unactivated alkenes. • The design of copper/N,N,N-ligand catalyst ensures its success. • Mild conditions make it operationally simple. A copper-catalyzed three-component radical trifluoromethylalkynylation of unactivated alkenes is realized from Togni-II reagent and readily available terminal alkynes under mild conditions to afford an array of β-trifluoromethylated alkynes. The utilization of a multidentate N,N,N-ligand is crucial for the efficient radical generation and the C(sp3)–C(sp) bond formation. Facile transformations of the difunctionalization products highlight its potential utility in the synthesis of various trifluoromethyl-containing building blocks. [Display omitted] [ABSTRACT FROM AUTHOR]

A general copper-catalyzed C(sp 3)−C(sp 2) cross-coupling of (hetero)benzyl bromides with the air- and moisture-stable aryl nucleophiles has been developed, providing a facile access to pharmaceutically useful 1,1-di(hetero)arylalkane and 1-aryl-1-heteroarylalkane scaffolds. Critical to the success is the utilization of a proline-based N,N,P-ligand to enhance the reducing capability of copper, thus easily converting benzyl bromides to the corresponding radical species via a single-electron transfer process under ambient conditions. The reaction features a broad substrate scope, covering (hetero)arylboronate esters, oxadiazoles, and benzo[ d ]oxazoles, as well as primary and secondary (hetero)benzyl bromides with excellent functional group tolerance. [Display omitted] [ABSTRACT FROM AUTHOR]