Project description:Herein, we communicate a selective and efficient protocol for oxidative arylating carbocyclization of enallenynes using O2 as the oxidant. The key to success for this aerobic transformation is the application of a specific electron transfer mediator (ETM), a bifunctional catalyst consisting of a metal-macrocycle and quinone moieties. This catalyst significantly facilitates the reoxidation of Pd0 to PdII under atmospheric pressure of O2 . Diverse functionalized enallenynes react with aryl boronic acids to afford the corresponding cyclic tetraenes in moderate to good yields.

| S-EPMC6471031 | biostudies-literature

Palladium-Catalyzed Oxidative Domino Carbocyclization-Arylation of Bisallenes.

Project description:Herein we report a highly efficient and site-selective palladium-catalyzed oxidative carbocyclization-arylation reaction of bisallenes and arylboronic acids under operationally simple conditions for the selective synthesis of cyclohexadiene derivatives. The palladium source and the solvent proved to be crucial for the selectivity and the reactivity displayed. Interestingly, in the absence of the nucleophile, an oxidative carbocyclization-β-elimination pathway predominates. The reaction conditions are compatible with a wide range of functional groups, and the reaction exhibits broad substrate scope. Furthermore, key information regarding the mechanism was obtained using control experiments and kinetic studies.

| S-EPMC5065722 | biostudies-literature

Palladium-Catalyzed Oxidative Carbocyclization-Borylation of Enallenes to Cyclobutenes.

Project description:A highly efficient palladium-catalyzed oxidative borylation of enallenes was developed for the selective formation of cyclobutene derivatives and fully-substituted alkenylboron compounds. Cyclobutenes are formed as the exclusive products in MeOH in the presence of H2 O and Et3 N, whereas the use of AcOH leads to alkenylboron compounds. Both reactions showed a broad substrate scope and good tolerance for various functional groups, including carboxylic acid ester, free hydroxy, imide, and alkyl groups. Furthermore, transformations of the borylated products were conducted to show their potential applications.

| S-EPMC5021125 | biostudies-literature

Supported Palladium Nanoparticles Catalyzed Intermolecular Carbopalladation of Nitriles and Organoboron Compounds.

Project description:The first heterogeneous catalyzed example for the direct synthesis of aromatic ketones via intermolecular carbopalladation of aliphatic nitriles and organoboron compounds was developed. This mild method proceeds with a supported palladium nanoparticles catalyst that could be reused and recycled five times. The fresh and used catalysts were characterized by XPS and TEM. The XPS analysis indicated that Pd0 was the active species for the reaction. This methodology provides a mild and cost-effective strategy for the efficient synthesis of ketones.

| S-EPMC9124771 | biostudies-literature

Palladium-catalyzed oxidative regio- and diastereoselective diarylating carbocyclization of dienynes.

Project description:Transmetallation: A highly regio- and diastereoselective carbocyclization involving a palladium-catalyzed 1,2-addition of two carbon atoms across a conjugated diene has been developed (see scheme). The reaction is performed with dienynes and an oxygen tether containing a terminal or internal triple bond.

| S-EPMC3743347 | biostudies-literature

Efficient Palladium-Catalyzed Aerobic Oxidative Carbocyclization to Seven-Membered Heterocycles.

Project description:The use of molecular oxygen in palladium-catalyzed oxidation reactions is highly widespread in organic chemistry. However, the direct reoxidation of palladium by O2 is often kinetically unfavored, thus leading the deactivation of the palladium catalyst during the catalytic cycle. In the present work, we report a highly selective palladium-catalyzed carbocyclization of bisallenes to seven-membered heterocycles under atmospheric pressure of O2 . The use of a homogenous hybrid catalyst (Co(salophen)-HQ, HQ=hydroquinone) significantly promotes efficient electron transfer between the palladium catalyst and O2 through a low-energy pathway. This aerobic oxidative transformation shows broad substrate scope and functional group compatibility and allowed the preparation of O-containing seven-membered rings in good yields in most cases.

| S-EPMC7894550 | biostudies-literature

Palladium-catalyzed intramolecular carbopalladation/cyclization cascade: access to polycyclic N-fused heterocycles.

Project description:An efficient palladium-catalyzed intramolecular carbopalladation/cyclization cascade toward tetra- and pentacyclic N-fused heterocycles has been developed. This transformation proceeds via the palladium-catalyzed coupling of aryl halides with internal propargylic esters or ethers followed by the 5-endo-dig cyclization leading to polycyclic pyrroloheterocycles in moderate to excellent yields.

| S-EPMC3131228 | biostudies-literature

Palladium(II)/Bronsted Acid-Catalyzed Enantioselective Oxidative Carbocyclization-Borylation of Enallenes.

Project description:An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Brønsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.

| S-EPMC4471548 | biostudies-literature

Control of selectivity in palladium-catalyzed oxidative carbocyclization/borylation of allenynes.

Project description: Not available

| S-EPMC3734627 | biostudies-literature