Ligand-enabled Ni-catalysed enantioconvergent intermolecular Alkyl-Alkyl cross-coupling between distinct Alkyl halides

Benzamide-Directed Hydroarylative Cross-Couplings Using Minimally Activated Alkenes: Enantioselective Synthesis of Tertiary and Quaternary Stereocenters

Ir-systems modified with ferrocene-based homochiral diphosphonite ligands, prepared from functionalized SPINOL derivatives, promote benzamide-directed hydroarylative cross-couplings involving minimally activated alkenes. The processes are highly branched selective and enantioselective. Accordingly, tertiary benzylic stereocenters are generated under byproduct-free conditions. This contrast with conventional cross-coupling approaches, which are less step and atom economical. Preliminary results show that the process extends to the formation of quaternary benzylic stereocenters.

Switchable Regiodivergent Reductive Alkyl-Alkyl Coupling by Nickel Catalysis: Sorting Different Alkyl-Nickel Intermediates

Site-selective and divergent functionalizations on saturated alkyl chain at specific unfunctionalized positions is a key challenge in organic chemistry and other related areas and offers unprecedented synthetic opportunities. Herein, a ligand-controlled Ni-catalyzed site-selective and divergent alkyl-alkyl reductive coupling between two different alkyl halides has been developed. Notably, the reaction finely tunes and recognizes thermodynamic favored α-aminoalkyl radicals over β-aminoalkyl radicals, and distal ipso-alkyl radicals to deliver chemo- and position-selective alkylation of unactivated α-H and β-H of amines under reductive conditions. Moreover, the reaction selectively functionalizes one alkyl chain over two migratable alkyl chains. By just switching the catalytic parameters, α- and β-alkylation of saturated C─H bonds, and ipso-alkyl-alkyl coupling allow for rapid access to three types of branched aliphatic amine architectures from identical starting materials.

Formal Umpolung Strategy for the Synthesis of α-Branched Amides via α-Sulfenylnitro Compounds

Amide compounds are essential structural motifs found in natural products, pharmaceuticals, peptides and materials. A novel formal umpolung strategy for an efficient synthesis of α-branched amides was developed, employing nitroalkenes, Grignard reagents and amines as reacting components. The synthesis involves the formation of α-sulfenylnitro intermediates, which undergo oxidative amidation under optimized conditions using tert-butyl hydroperoxide (TBHP) as an oxidant and K2CO3 as a base. The key intermediate, an α-sulfenylnitro compound, was successfully synthesized in a one-pot operation. This methodology demonstrates a broad substrate scope, accommodating various amines, including primary and secondary amines as well as amino acid derivatives, and yielding the corresponding α-branched amides in high efficiency. The sulfenyl nitro scaffold proved particularly effective, offering both stability and reactivity. The developed process simplifies the preparation of α-branched amides and expands the accessible structural diversity.

Synthesis of α-N-Heteroaryl Ketones by Nickel-Catalyzed Chemo-, Regio- and Enantioselective Carbonylation of Alkenes and N-Alkenyl Heteroarenes

Enantioenriched α-aminoketones serve as important substructures in life science and precursors for the synthesis of diverse value-added targets in organic and biochemistry. However, direct access to enantioenriched α-aminoketones from simple and readily available starting materials remains a formidable challenge. Herein, we report an unprecedented nickel-catalyzed asymmetric cross-coupling protocol for the synthesis of enantioenriched α-N-heteroaryl ketones from alkenes and enamines in the presence of a carbon monoxide surrogate. The success of this reaction relies on the sorting of two different alkenes along with the control of regio- and enantioselectivity. This reductive-oxidative carbonylation of enamines and unactivated alkenes featuring the use of a carbon monoxide surrogate allows for the gas-free streamlined assembly of enantioenriched α-N-heteroaryl ketones from two distinct alkenes.

Dual Nickel- and Photoredox-Catalyzed Asymmetric Reductive Cross-Coupling To Access Chiral Secondary Benzylic Alcohols

Transition-metal-catalyzed asymmetric cross-coupling represents a powerful strategy for C-C bond formation and the synthesis of enantiomerically pure molecules. Here, we report a dual nickel/photoredox-catalyzed enantioselective reductive cross-coupling of aryl halides with α-bromobenzoates, readily generated from aliphatic aldehydes, to provide diverse chiral secondary benzylic alcohols that are important motifs in bioactive natural products and pharmaceuticals. This dual catalytic system features mild conditions, good functional group tolerance, broad substrate scope, excellent enantiocontrol, and avoidance of stoichiometric metal reductants, presenting great potential for late-stage functionalization of complex molecules.

Dual Nickel- and Photoredox-Catalyzed Asymmetric Reductive Cross-Couplings: Just a Change of the Reduction System?

ConspectusIn recent years, nickel-catalyzed asymmetric coupling reactions have emerged as efficient methods for constructing chiral C(sp3) carbon centers. Numerous novel approaches have been reported to rapidly construct chiral carbon-carbon bonds through nickel-catalyzed asymmetric couplings between electrophiles and nucleophiles or asymmetric reductive cross-couplings of two different electrophiles. Building upon these advances, our group has been devoted to interrogating dual nickel- and photoredox-catalyzed asymmetric reductive cross-coupling reactions.In our endeavors over the past few years, we have successfully developed several dual Ni-/photoredox-catalyzed asymmetric reductive cross-coupling reactions involving organohalides. While some probably think that this system is just a change of the reduction system from traditional metal reductants to a photocatalysis system, a question that we also pondered at the beginning of our studies, both the achievable reaction types and mechanisms suggest a different conclusion: that this dual catalysis system has its own advantages in the chiral carbon-carbon bond formation. Even in certain asymmetric reactions where the photocatalysis regime functions only as a reducing system, the robust reducing capability of photocatalysts can effectively accelerate the regeneration of low-valent nickel species, thus expanding the selectable scope of chiral ligands. More importantly, in many transformations, besides reducing nickel catalysts, the photocatalysis system can also undertake the responsibility of alkyl radical formation, thereby establishing two coordinated, yet independent catalytic cycles. This catalytic mode has been proven to play a crucial role in achieving diverse asymmetric coupling reactions with great challenges.In this Account, we elucidate our understanding of this system based on our experience and findings. In the Introduction, we provide an overview of the main distinctions between this system and traditional Ni-catalyzed asymmetric reductive cross-couplings with metal reductants and the potential opportunities arising from these differences. Subsequently, we outline various chiral carbon-carbon bond-forming types obtained by this dual Ni/photoredox catalysis system and their mechanisms. In terms of chiral C(sp3)-C(sp2) bond formation, extensive discussion focuses on the asymmetric arylations of α-chloroboronates, α-trifluoromethyl alkyl bromides, α-bromophosphonates, and so on. In the realm of chiral C(sp3)-C(sp) bond formation, asymmetric alkynylations of α-bromophosphonates and α-trifluoromethyl alkyl bromides have been presented herein. Regarding C(sp3)-C(sp3) bond formation, we take the asymmetric alkylation of α-chloroboronates as a compelling example to illustrate the great efficiency of this dual catalysis system. This summary would enable a better grasp of the advantages of this dual catalysis system and clarify how the photocatalysis regime facilitates enantioselective transformations. We anticipate that this Account will offer valuable insights and contribute to the development of new methodologies in this field.

Hydrogen Source Tuned Regiodivergent Asymmetric Hydroalkylations of 2-Substituted 1,3-Dienes with Aldehydes by Cobalt-Catalysis

Catalytic methods allowing for the reliable prediction and control of diverse regioselectivity along with the control of enantioselectivity to access different regio- and enantiomers by switching the least reaction parameters are one of the most attractive ways in organic synthesis, which provide access to diverse enantioenriched architectures from identical starting materials. Herein, a Co-catalyzed regiodivergent and enantioselective reductive hydroalkylation of 1,3-dienes with aldehydes has been achieved, furnishing different enantioenriched homoallylic alcohol architectures in good levels of enantioselectivity. The reaction features the switch of regioselectivity tuned by the selection of proton source. The use of an acid as proton source provided asymmetric 1,2-hydroalkylation products under reductive conditions, yet asymmetric 4,3-hydroalkylation products were obtained with silane as hydride source. This catalytic protocol allows for the access of homoallylic alcohols with two continuous saturated carbon centers in good levels of regio-, diastereo-, and enantioselectivity.

Enantioselective Csp3-Csp3 formation by nickel-catalyzed enantioconvergent cross-electrophile alkyl-alkyl coupling of unactivated alkyl halides

The pervasive occurrence of saturated stereogenic carbon centers in pharmaceuticals, agrochemicals, functional organic materials, and natural products has stimulated great efforts toward the construction of such saturated carbon centers. We report a reaction mode for the enantioselective construction of alkyl-alkyl bond to access saturated stereogenic carbon centers by asymmetric reductive cross-coupling between different alkyl electrophiles in good yields with great levels of enantioselectivity. This reaction mode uses only alkyl electrophiles for enantioselective C_sp3-C_sp3 bond-formation, rendering reductive alkyl-alkyl cross-coupling as an alternative to traditional alkyl-alkyl cross-coupling reactions between alkyl nucleophiles and alkyl electrophiles to access saturated stereogenic carbon centers without the use of organometallic reagents. The reaction displays a broad scope for two alkyl electrophiles with good functional group tolerance. Mechanistic studies reveal that the reaction undergoes a single electron transfer that enabled the reductive coupling pathway to form the alkyl-alkyl bond.