Palladium‐Catalyzed C−H Alkenylation of Arenes with Alkynes: Stereoselective Synthesis of Vinyl Chlorides via a 1,4‐Chlorine Migration

Z-selective radical difunctionalization of aromatic alkynes: synthesis of multi-substituted triarylethenes

An efficient method for the radical difunctionalization of aromatic alkynes has been developed, resulting in the synthesis of a range of valuable triarylethenes. This approach utilizes strategically designed aryldiazonium salts with tertiary alcohol substitution as bifunctional reagents, along with cost-effective cuprous chloride as a catalyst. The method demonstrates remarkable Z-selectivity and is capable of gram-scale preparation. Additionally, a novel spin-trapping reagent has been developed based on the synthesized product.

Ni-catalyzed hydroarylation of alkynes with unactivated β-C(sp2)-H bonds

Hydroarylation of alkynes with unactivated C(sp²)-H bonds via chelated C-H metalation mainly occurs at γ-position to the coordinating atom of directing groups via stable 5-membered metallacycles, while β-C(sp²)-H bond-involved hydroarylation has been a formidable challenge. Herein, we used a phosphine oxide-ligated Ni-Al bimetallic catalyst to enable β-C-H bond-involved hydroarylations of alkynes via a rare 7-membered nickelacycle.

Binary-Acid Catalysis with Sc(OTf)3/TfOH in the Alkenylation of Arenes with Alkynes

Herein we report binary acid Sc(OTf)₃/TfOH-catalyzed alkenylation of arenes with alkynes. In this system, the high-energy vinyl carbocations with activated and weakly coordinating trifluoromethanesulfonate anions by Lewis acid Sc(III) can undergo facile Friedel-Crafts reactions with arenes to give the desired adducts in up to 90% yield and with high Z-selectivity.

C-H Bond Functionalization of (Hetero)aryl Bromide Enabled Synthesis of Brominated Biaryl Compounds

Aryl bromide is one of the most important compounds in organic chemistry, because it is widely used as synthetic building blocks enabling quick access to a wide array of bioactive molecules, organic materials, and polymers via the versatile cutting-edge transformations of C-Br bond. Direct C-H bond functionalization of aryl bromide is considered to be an efficient way to prepare functionalized aryl bromides; however, it is rarely explored possibly due to the relatively low reactivity of aryl bromide toward C-H bond activation. We herein report a palladium-catalyzed coupling reaction between aryl iodide and aryl bromide for preparing brominated biaryl compounds via a silver-mediated C-H bond activation pathway.

Palladium-Catalyzed Regiospecific peri- and ortho-C-H Oxygenations of Polyaromatic Rings Mediated by Tunable Directing Groups

An efficient divergent approach of Pd-catalyzed C-H oxygenation of polyaromatic rings is described. Reversible directing groups enable regiospecific peri- and ortho-oxygenation to readily access a wide array of polyaromatic phenols without pre- and postmanipulation of directing groups. The systematic mechanistic investigation, including deuterium-labeling experiments, palladacycle trapping, and DFT calculations, reveals that the tunable ligand-assisted C-H bond cleavage played a crucial role during the reaction process.

Radical 1,2-addition of bromoarenes to alkynes via dual photoredox and nickel catalysis

A 1,2-addition of aryl bromides to alkynes enabled by the photocatalytic generation of bromine radicals via photoredox and nickel catalysis is reported.

Visible Light-Enabled sp3 -C-H Functionalization with Chloro- and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes

An unprecedented direct atom-economic chemo- and regioselective hydroalkylation of chloroalkynes and an sp3 -C-H alkynylation of bromoalkynes was achieved. The reaction partners are unfunctionalized ethers, alcohols, amides, and even non-activated hydrocarbons. We found that a household fluorescent bulb was able to excite a diaryl ketone, which then selectively abstracts a H-atom from an sp3 -C-H bond. The product of a formal alkyne insertion into the sp3 -C-H bond was obtained with chloroalkynes, providing valuable vinyl chlorides. The photo-organocatalytic hydrogen atom transfer strategy gives rise to a broad range of diversely functionalized olefins. When bromoalkynes are applied in the presence of a base, a chemoselectivity switch to an alkynylation is observed. This reaction can even be performed for the alkynylation of unactivated sp3 -C-H bonds, in this case with a preference of the more substituted carbon. Accompanying quantum chemical calculations indicate a vinyl radical intermediate with pronounced linear coordination of the carbon radical center, thus enabling the formation of both diastereoisomers after H-atom abstraction, suggesting that the (Z)-diastereoisomer is preferred, which supports the experimentally observed (E/Z)-distribution.

Highly selective hydrosilylation of equilibrating allylic azides

The Pt-catalyzed hydrosilylation of equilibrating allylic azides is reported. The reaction provides only one out of four possible hydrosilylation products in good yields and with very high chemoselectivity (alk-1-ene vs. alk-2-ene), regioselectivity (linear vs. branched), and excellent functional group tolerance.

Suzuki-Miyaura Coupling Enabled by Aryl to Vinyl 1,4-Palladium Migration

The Suzuki-Miyaura coupling is a fundamentally important transformation in modern organic synthesis. The development of new reaction modes for new chemical accessibility and higher synthetic efficiency is still the consistent pursuance in this field. An efficient Suzuki-Miyaura coupling enabled by a controllable 1,4-palladium migration was realized to afford stereodefined multisubstituted olefins and 1,3-dienes. The reaction exhibits remarkable broad substrate scope, excellent functional-group tolerance, versatile conversion with obtained products, and easy scalability. The practicality of this method is highlighted by the aggregation-induced emission feature of the produced olefins and 1,3-dienes, as well as the capability of affording geometric isomer pairs with a marked difference on photoluminescent quantum yield values.