Diastereodivergent and Enantioselective Synthesis of Homoallylic Alcohols via Nickel-Catalyzed Borylative Coupling of 1,3-Dienes with Aldehydes

Synthesis of 1,5-Diamino-Substituted 1,3-Dienes via Rhodium(II)-Catalyzed Tandem Reactions of 1-Cyclopropylethylarenes

Herein, (E,E)-1,5-diamino-1,3-dienes are stereoselectively synthesized from substituted aryl derivatives via a rhodium(II)-catalyzed C(sp3)-H functionalization involving a cascade of cyclopropane ring expansion, cyclobutene formation, cyclobutene to 1,3-diene conversion, and regioselective diamination. Mechanistic studies show this one-pot process proceeds through hydrogen atom transfer (HAT), radical-polar crossover (RPC), elimination, electrocyclic ring-opening, and radical addition, underscoring rhodium(II)'s role in radical-mediated catalysis beyond traditional rhodium(II) nitrenoid chemistry.

Ligand-Controlled Regiodivergent Carbosilylation of 1,3-Dienes via Nickel-Catalyzed Three-Component Coupling Reactions

The regiodivergent carbosilylation of 1,3-dienes presents a formidable challenge due to inherently complex selectivity control over multiple potential reaction pathways. Here, we report a ligand-controlled, regiodivergent carbosilylation of 1,3-dienes with aldehydes and silylboranes, achieving unprecedented site-selectivity using nickel catalysts with distinct phosphine ligands. The use of triethylphosphine promotes 4,3-addition selectivity, while employing (2-biphenyl)dicyclohexylphosphine facilitates 4,1-addition selectivity. This method displays excellent regio- and diastereoselectivity, as well as a broad substrate scope and substantial functional group tolerance. Mechanistic studies indicate that the ligand choice is crucial for directing the reaction pathway and stabilizing π-allyl-nickel intermediates. Our protocol provides a practical and efficient approach to synthesizing valuable functionalized allylsilanes, which are important in various synthetic applications.

Nickel-Catalyzed Hydrocarbamoylation of Alkenes with Isocyanates

The hydrocarbamoylation of alkenes with isocyanates is a promising method for synthesizing amides. However, applying this strategy to more inert, simple alkenes, such as styrenes, α-olefins, and internal alkenes, poses significant challenges. Here, we report the first nickel-catalyzed hydrocarbamoylation of alkenes with isocyanates, facilitated by triethoxysilane to reduce nickelacycle intermediates. By switching ligands─including 6,6'-dimethyl-2,2'-bipyridine and N-heterocyclic carbene─this method efficiently produces amides from a diverse array of alkenes, including styrenes, α-olefins, internal alkenes, and gaseous olefins.

Photoredox/Cobalt-Catalyzed Chemo-, Regio-, Diastereo- and Enantioselective Reductive Coupling of 1,1-Disubstituted Allenes and Cyclobutenes

A dual photoredox/cobalt-catalyzed protocol for chemo-, regio-, diastereo- and enantioselective reductive coupling of 1,1-disubstituted allenes and cyclobutenes through chemo-, regio-, diastereo- and enantioselective oxidative cyclization followed by stereoselective protonation promoted by a chiral phosphine-cobalt complex is presented. Such process represents an unprecedented reaction pathway for cobalt catalysis that enables selective transformation of the less sterically congested alkenes of 1,1-disubstituted allenes with cyclobutenes, incorporating a broad scope of tetrasubstituted alkenes into the cyclobutane scaffolds in up to 86 % yield, >98 : 2 chemo- and regioselectivity, >98 : 2 dr and >99.5:0.5 er. Functionalization delivered a variety of enantioenriched cyclobutanes that are otherwise difficult to access. Preliminary mechanistic studies revealed that the reactions proceeded through oxidative cyclization followed by protonation and protonation might be the rate-determining step.

Cobalt-Catalyzed Regio-, Diastereo- and Enantioselective Reductive Coupling of 1,3-Dienes and Aldehydes

Catalytic regio-, diastereo- and enantioselective reductive coupling of 1,3-dienes and aldehydes through regio- and enantioselective oxidative cyclization followed by regio- and diastereoselective protonation promoted by a chiral phosphine-cobalt complex is presented. Such processes represent an unprecedented reaction pathway for cobalt catalysis that enable selective transformation of the more substituted alkene in 1,3-dienes, affording a broad scope of bishomoallylic alcohols without the need of pre-formation of stoichiometric amounts of sensitive organometallic reagents in up to 98 % yield, >98 : 2 regioselectivity, >98 : 2 dr and 98 : 2 er. Application of this method to construction of axial stereogenicity and deuterated stereogenic center provided a wide range of multifunctional chiral building blocks that are otherwise difficult to access. DFT calculations revealed the origin of regio- and stereoselectivity as well as a unique oxidative cyclization mechanism for cobalt catalysis.

Enantioselective Synthesis of vic-Aminoalcohol Derivatives by Nickel-Catalyzed Reductive Coupling of Aldehydes with Protected Amino-pentadienoates

A VAPOL-derived phosphoramidite ligand is uniquely effective at reverting the regiochemical course of nickel-catalyzed reactions of aldehydes with carbamate-protected 5-amino-2,4-pentadienoates as "push/pull" dienes; the ensuing carbonyl α-amino-homoallylation reaction affords anti-configured vic-aminoalcohol derivatives in good yields with high optical purity. The reductive coupling is conveniently performed with a bench-stable Ni(0) precatalyst and Et3B as the promoter.

Copper(I)-Catalyzed Asymmetric Nucleophilic Addition to Aldehydes with Skipped Enynes

The development of sustainable and novel strategies for constructing complex chiral molecules with versatile transformation potential is a long-term pursuit in the chemistry community. We report a copper(I)-catalyzed enyne addition to aldehydes under proton-transfer conditions, unlike previous examples which were limited to the use of preformed reactive nucleophiles containing allylic heteroatoms or electron-withdrawing groups. This protocol provides an efficient platform for installing chiral allylic alcohol moieties with a broad substrate scope and high regio-, stereo-, and enantioselectivity.

Structural Basis of Cucurbituril-Containing Self-Assembled Supramolecular Chiral Materials

Macrocycle-based host-guest complexation offers an intriguing protocol in producing chiroptical materials, while the bulky size and dynamic exchange between hosts and guests hinders the ordered aggregation to afford the long-range chiral arrangement. It remains great challenges in assembling cucurbit[n]urils (CB[n]s) included complexes to induce supramolecular chirality ascribed to the excellent water solubility and flexible packing. Herein, we unveiled the structural basis on the formation of chiroptical coassemblies from CB[n] (n=6, 7) complexes. Perylene diimides (PDIs) with cationic chiral pendants formed complexes in the aqueous media, which selectively showed chiroptical properties. Chlorination at the bay position, increasing alkyl length of cationic chiral pendants or reducing the number of polyaromatic rings would hinder the chiral aggregation. In a comprehensive manner, CB[6] favors ordered aggregation into one-dimensional fibrous nanoarchitectures that greatly facilitates the supramolecular chirality. In contrast, CB[7] with larger cavity and water solubility shrinks the ordered arrangement of complexes, reducing the formation possibility of supramolecular chiral nanoarchitectures. This work suggests the great potential of CB[6] in the preparation and manipulation of supramolecular chiral assemblies, shedding light on the macrocycle-based functional chiroptical materials.

Redox-Neutral Coupling of Allyl Alcohols with Trifluoromethyl Ketones via Synergistic Ni-Ti Bimetallic Catalysis

A redox-neutral coupling of allyl alcohols with trifluoromethyl ketones has been developed via Ni-Ti bimetallic catalysis. This innovative method allows for the efficient synthesis of various β-tertiary trifluoromethyl alcohol-substituted ketones with yields of up to 98%. The reaction is scalable and compatible with a wide range of substrates, including complex bioactive molecules. Mechanistic studies suggest that the rate-determining step involving β-H elimination and the presence of the Ti-based Lewis acid, as well as a hydroxyl group on the substrates, is crucial for driving the reactivity of this transformation.

Stereoconvergent and Enantioselective Synthesis of Z-Homoallylic Alcohols via Nickel-Catalyzed Reductive Coupling of Z/E-1,3-Dienes with Aldehydes

Stereoconvergent reactions enable the transformation of mixed stereoisomers into well-defined, chiral products─a crucial strategy for handling Z/E-mixed olefins, which are common but challenging substrates in organic synthesis. Herein, we report a stereoconvergent and highly enantioselective method for synthesizing Z-homoallylic alcohols via the nickel-catalyzed reductive coupling of Z/E-mixed 1,3-dienes with aldehydes. This process is enabled by an N-heterocyclic carbene ligand characterized by C2-symmetric backbone chirality and bulky 2,6-diisopropyl N-aryl substituents. Our method achieves excellent stereocontrol over both enantioselectivity and Z-selectivity in a single step, producing chiral Z-homoallylic alcohols that are valuable in natural products and pharmaceuticals.

Palladium(0) π-Lewis Base Catalysis: Concept and Development

The development of a new catalytic strategy plays a vital role in modern organic chemistry since it permits bond formation in an unprecedented and more efficient manner. Although the application of preformed metal complexes as π-base-activated reagents have enabled diverse transformations elegantly, the concept and strategy by directly utilizing transition metals as efficient π-Lewis base catalysts remain underdeveloped, especially in the field of asymmetric catalysis. Here, we outline our perspective on the discovery of palladium(0) as an efficient π-Lewis base catalyst, which is capable of increasing the highest occupied molecular orbital (HOMO) energy of both electron-neutral and electron-deficient 1,3-dienes and 1,3-enynes upon flexible η2-complexes formed in situ and resultant π-backdonation. Thus, fruitful carbon-carbon-forming reactions with diverse electrophiles can be achieved enantioselectively in a vinylogous addition pattern, which is conceptually different from the classical oxidative cyclization mechanism. Emphasis will be given to the concept and mechanism elucidation, catalytic features, and reaction design together with perspective on the further development of this emerging field.

Ligand-Controlled Regiodivergent Nickel-Catalyzed Hydroaminoalkylation of Unactivated Alkenes

Ligand modulation of transition-metal catalysts to achieve optimal reactivity and selectivity in alkene hydrofunctionalization is a fundamental challenge in synthetic organic chemistry. Hydroaminoalkylation, an atom-economical approach for alkylating amines using alkenes, is particularly significant for amine synthesis in the pharmaceutical, agrochemical, and fine chemical industries. However, the existing methods usually require specific substrate combinations to achieve precise regio- and stereoselectivity, which limits their practical utility. Protocols allowing for regiodivergent hydroaminoalkylation from the same starting materials, controlling both regiochemical and stereochemical outcomes, are currently absent. Herein, we report a ligand-controlled, regiodivergent nickel-catalyzed hydroaminoalkylation of unactivated alkenes with N-sulfonyl amines. The reaction initiates with amine dehydrogenation and involves aza-nickelacycle intermediates. Tritert-butylphosphine promotes branched regioselectivity and syn diastereoselectivity, whereas ethyldiphenylphosphine enables linear selectivity, yielding regioisomers with inverse orientation. Systematic evaluation of diverse monodentate phosphine ligands reveals distinct regioselectivity cliffs, and % Vbur (min), a ligand steric descriptor, was established as a predictive parameter correlating ligand structure to regioselectivity. Computational investigations supported experimental findings, offering mechanistic insights into the origins of regioselectivity. Our method provides an efficient and predictable route for amine synthesis, demonstrating broad substrate scope, excellent tolerance toward various functional groups, and practical advantages. These include the use of readily available starting materials and cost-effective nickel(II) salts as precatalysts.

Aminoalcohol derivatives by nickel-catalyzed enantioselective coupling of imines and dienol ethers

The reductive coupling of dienol ethers with N-tosylimines catalyzed by Ni(0) in the presence of a VAPOL-derived phosphoramidite ligand follows an unprecedented regiochemical course; it furnishes syn-configured 1,2-aminoalcohol derivatives in good chemical yields with up to 94% ee.