An Active Palladium Colloidal Catalyst for the Selective Oxidative Heterocoupling of (Hetero)Aryl Boronic Acids

Abstract

A highly selective oxidative heterocoupling protocol for (hetero)aryl boronic acids with an active palladium colloidal catalyst was developed. The judicious choice of electronically different aryl boronic acids made possible such couplings under mild conditions, with air as oxidant, while embracing a wide substrate scope. This successful approach further allowed the development of a unique one-pot sequential oxidative heterocoupling/Suzuki-Miyaura cross-coupling tandem process for accessing substituted terphenyls.

Pd‐Colloids‐Catalyzed/Ag2O‐Oxidized General and Selective Esterification of Benzylic Alcohols

“…One contribution to the development of novel C−C bond forming technologies using active palladium colloidal catalysts from our group was published covering the efficient homocoupling and heterocoupling of arylboronic acids. The isolation and the complete characterization of the synthesized palladium colloidal catalyst was possible by utilizing techniques such as TEM, HRTEM, XRD, XPS, EDS and EXAFS …”

“…[44][45][46] Fine tuningt hese factors should allow the development of superior,m ore efficient catalytic technologies for CÀCb ond formation processes.O ne contribution to the development of novel CÀCbond forming technologies using active palladium colloidal catalysts from our group was published covering the efficient homocoupling and heterocouplingo fa rylboronic acids.T he isolation and the complete characterization of the synthesized palladium colloidal catalystw as possible by utilizing techniques such as TEM, HRTEM, XRD, XPS, EDS and EXAFS. [43,47] Oxidative esterification of benzyl alcohols employing metal nanoparticles (MNPs)h as been well-known for the past several years. [48] Although the MNPs employed were usually expensive such as Au [18,[49][50][51][52] and Ag, [53] they were also supported on certain frameworks [54,55] thereby leading to at edious synthetic route for the preparation of thesec atalystsandm aking the reproducibility of protocolr elativelyd ifficult for other researchers.…”

Carbazole‐Based N‐Heterocyclic Carbenes for the Promotion of Copper‐Catalyzed Palladium‐Free Homo‐/Hetero‐Coupling of Alkynes and Sonogashira Reactions

“…Unsymmetrical diynes‐via heterocoupling of two different alkynes is a synthetic challenge that could be undertaken in a similar manner to that involving the heterocoupling of Grignard reagents, Zinc reagents, boronic acids . An efficient way to promote the hetero‐coupling‐vs homo‐coupling is to employ electronically distinct alkynes (i. e. electron‐withdrawing and electron‐donating substituents bearing alkynes) which modulates the electronic factors on the catalytically active metal center providing the hetero‐coupled product preferentially over the homo‐coupled one.…”

Transition Metal-Based Nanoparticles Catalyzed Esterification Reactions

“…At the end of 24 h, Fe@Si nanoparticles thus formed were recovered using a magnet, washed thoroughly with alcohol and diethyl ether and then dried. The produce was thoroughly washed with methanol and water and dried in an oven 8 h. 51 Under the following reaction conditions: 1 mmol aldehyde, 2 mL of alcohol, 2 mmol of 33% hydrogen peroxide, 0.01 mmol of 10 mol% Fe nanoparticles at room temperature for 20 h, the reaction was monitored by Thin Layer Chromatography(TLC). The reaction was found to be efficient with a majority of aromatic systems as the presence of electron-withdrawing or electron releasing groups did not affect the yield of the products.…”