Redox-Neutral 1,4-Dicarbonfunctionalization of 1,3-Butadiene by Merging Photoredox and Nickel Catalysis

Reactivity Tuning for Selective Aldimino-Sulfonylation of Styrenes by Photocatalytic Activation of Sulfonyl Aldimines

Imino-sulfonylation of styrene represents a powerful method for constructing highly functionalized molecules, while only diphenyl imines were able to be employed in previous reports. By modulating the electron property of the styrene, visible-light-mediated radical/radical cross-coupling of the aldiminyl radical and carbon-centered radical was achieved to synthesize diverse aldimine-embedded sulfones by using sulfonyl aldimines and α-trifluoromethylstyrenes. One-pot oxidation of the aldimines delivered Ritter-type amidation products without the need for excessive nitriles as solvent. Furthermore, this protocol took advantage of simple reaction conditions, good substituent diversity, and high atom economy to broaden the research of aldiminyl radicals and amination of alkenes.

Selective Alkylarylation Difunctionalization of 1,3-Butadienes via Nickel/Photoredox Dual Catalysis

Photocatalytic multicomponent reactions are at the forefront of organic synthesis. In recent years, the dicarbofunctionalization of olefins has received significant attention, with nickel serving as a key transition metal catalyst under photochemical conditions. However, achieving regioselective 1,4-alkylarylation of dienes with alkyl and aryl bromides remains challenging. In this work, we present a Ni/photoredox dual catalysis approach for the regioselective alkylarylation of dienes, offering a mild reaction that eliminates the need for stochiometric metal reductants. Broad substrate scope and mechanistic investigations are presented that support the proposed reaction mechanism.

Dialkylation of 1,3-Dienes with Aldehydes and Cyclopropanols toward Homoallylic Alcohols by Dual Photoredox and Chromium Catalysis

A visible-light-induced three-component coupling of aldehydes, 1,3-dienes, and cyclopropyl alcohols using dual photoredox and chromium catalysis is herein described. This efficient protocol achieves the dialkylation of 1,3-dienes toward 1,4-disubstituted homoallylic alcohols in moderate to good yields with excellent regioselectivity, featuring mild reaction conditions, good functional group tolerance, and gram-scale synthesis. Mechanistic study suggests that photoinduced sequential ring opening of cyclopropyl alcohol and radical and nucleophilic cascade addition are involved in the catalytic cycle.

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.

Photoinduced Pd-Catalyzed 1,4-Dicarbofunctionalization of 1,3-Butadienes via Aliphatic C-H Bond Elaboration

A three-component coupling strategy for 1,4-dicarbofunctionalization of 1,3-butadiene with C-H bearing substrates has been developed using photoinduced Pd catalysis, with aryl bromide serving as the hydrogen atom transfer (HAT) reagent. This photocatalytic coupling process achieves functionalized oxindole motifs in good yield and regioselectivity under mild reaction conditions. The versatility and synthetic utility of this method are demonstrated through the addition of a variety of C-H-bearing partners and various oxindole substrates to both substituted and unsubstituted butadiene.

Photoinduced Decatungstate Anion-Catalyzed 1,4-Difunctionalization of 1,3-Butadienes via C-H Activation

This paper outlines an innovative three-component coupling strategy for the 1,4-difunctionalization of 1,3-butadiene, utilizing sodium decatungstate (NaDT) as a hydrogen atom transfer (HAT) photocatalyst. The photoinduced process efficiently generates homoallylic amino acid esters with 100% atom economy, employing readily available components under mild reaction conditions. This light-induced protocol eliminates the need for an additional transition metal catalysts, additives, or equivalent reducing agents. The study explored various C(sp3)-H bearing partners, butadienes, and α-iminoesters, demonstrating the versatility and synthetic utility of this method.

Copper-Catalyzed Asymmetric Acylboration of 1,3-Butadienylboronate with Acyl Fluorides

We report herein a Cu-catalyzed regio-, diastereo- and enantioselective acylboration of 1,3-butadienylboronate with acyl fluorides. Under the developed conditions, the reactions provide (Z)-β,γ-unsaturated ketones bearing an α-tertiary stereocenter with high Z-selectivity and excellent enantioselectivities. While direct access to highly enantioenriched E-isomers was not successful, we showed that such molecules can be synthesized with excellent E-selectivity and optical purities via Pd-catalyzed alkene isomerization from the corresponding Z-isomers. The orthogonal chemical reactivities of the functional groups embedded in the ketone products allow for diverse chemoselective transformations, which provides a valuable platform for further derivatization.