Palladium-catalyzed borylation of aryl (pseudo)halides and its applications in biaryl synthesis

Recent Expedition in Pd- and Rh-Catalyzed C(Ar) -B Bond Formations and Their Applications in Modern Organic Syntheses

Transition metal-catalyzed borylation has emerged as a powerful and versatile strategy for synthesizing organoboron compounds. These compounds have found widespread applications in various aspects, including organic synthesis, materials science, and medicinal chemistry. This review provides a concise summary of the recent advances in palladium- and rhodium-catalyzed borylation from 2013 to 2023. The review covers the representative examples of catalysts, substrates scope and reaction conditions, with particular emphasis on the development of catalyst systems, such as phosphine ligands, NHC-carbene, and more. The diverse array of borylative products obtained for further applications in Suzuki-Miyaura coupling, and other transformations, are also discussed. Future directions in this rapidly evolving field, with the goal of designing more efficient, selective borylation methodologies are highlighted, too.

Regioselective Pd-Catalyzed Suzuki–Miyaura Borylation Reaction for the Dimerization Product of 6-Bromoimidazo[1,2-a]pyridine-2-carboxylate: Mechanistic Pathway, Cytotoxic and Tubercular Studies

In the pharmaceutical industry, boronic acid and esters play an important role in API-based synthesis. The most efficient way of preparing various active agents is palladium-catalyzed Suzuki–Miyaura borylation reactions. Herein, we report the formation of dimerization product [6,6′-biimidazo[1,2-a]pyridine]-2,2′-dicarboxamide derivatives 7a–j from 6-bromoimidazo[1,2-a]pyridine-2-carboxylate by employing the same conditions. A regioselective borylation of ethyl 6-bromoimidazo[1,2-a]pyridine-2-carboxylate (3) was examined for the formation of ethyl 6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)imidazo[1,2-a]pyridine-2-carboxylate (4a) but it was found to be directed towards the dimerization product 5. The nitrogen-rich system was incorporated into potential anti-cancer and anti-TB agents through acid amine coupling reactions between acid 6 and various amines (dialkyl/cyclic sec./tert.) to form the final adducts 7. Five derived scaffolds were identified as moderately active in TB activity against the H37Rv strain, while two compounds were found to be particularly potent in NCI-60 anti-cancer screening in nine cancer panels.

Nickel-Catalyzed Ipso-Borylation of Silyloxyarenes via C-O Bond Activation

The conversion of silyloxyarenes to boronic acid pinacol esters via nickel catalysis is described. In contrast to other borylation protocols of inert C-O bonds, the method is competent in activating the carbon-oxygen bond of silyloxyarenes in isolated aromatic systems lacking a directing group. The catalytic functionalization of benzyl silyl ethers was also achieved under these conditions. Sequential cross-coupling reactions were achieved by leveraging the orthogonal reactivity of silyloxyarenes, which could then be functionalized subsequently.