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

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

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 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(II)-Catalyzed Tandem Oxidative Acetoxylation/ortho C-H Activation/Carbocyclization of Arylallenes.

Project description:Herein we report an example of tandem oxidative acetoxylation/carbocyclization of arylallenes 1 using Pd(OAc)2. The catalytic protocol is highly selective and provides access to new C-C and C-O bonds leading to a carbocyclization. The reaction proceeds via C-H activation by Pd. Mechanistic investigations show that the C-H activation is not the rate-limiting step and indicate that the reaction proceeds via acetoxylation of the allene.

| S-EPMC4557776 | biostudies-literature

Efficient Palladium-Catalyzed Aerobic Arylative Carbocyclization of Enallenynes.

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 borylation of primary alkyl bromides.

Project description:A mild Pd-catalyzed process for the borylation of alkyl bromides has been developed using bis(pinacolato)diboron as a boron source. This process accommodates the use of a wide range of functional groups on the alkyl bromide substrate. Primary bromides react with complete selectivity in the presence of a secondary bromide. The generality of this approach is demonstrated by its extension to the use of alkyl iodides and alkyl tosylates, as well as borylation reactions employing bis(neopentyl glycolato)diboron as the boron source.

| S-EPMC3432578 | biostudies-literature

Palladium-catalyzed carbocyclization of alkynyl ketones proceeding through a carbopalladation pathway.

Project description: Not available

| S-EPMC3132813 | biostudies-literature