Preformed Pd(II) Catalysts Based on Monoanionic [N,O] Ligands for Suzuki-Miyaura Cross-Coupling at Low Temperature

• Published in: Catalysts Vol. 13; no. 2; p. 303
• Main Authors: Andrews, Matthew J., Brunen, Sebastian, McIntosh, Ruaraidh D., Mansell, Stephen M.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.01.2023
• Subjects: Acids; Aniline; Aromatic compounds; aryl Halide; Bromides; Catalysis; Catalysts; Chelation; Chemical reactions; Chemical synthesis; Cross coupling; Esters; High temperature; Ligands; Low temperature; Palladium; Palladium catalysts; Room temperature; Solvents; Substrates; sustainable; Suzuki-Miyaura; Time; United Kingdom
• ISSN: 2073-4344; 2073-4344
• DOI: 10.3390/catal13020303

This paper describes the synthesis and catalytic testing of a palladium complex with a 5-membered chelating [N,O] ligand, derived from the condensation of 2,6-diisopropylphenyl aniline and maple lactone. This catalyst was active towards the Suzuki-Miyaura cross-coupling reaction, and its activity was optimised through the selection of base, solvent, catalytic loading and temperature. The optimised conditions are mild, occurring at room temperature and over a short timescale (1 h) using solvents considered to be ‘green’. A substrate scope was then carried out in which the catalyst showed good activity towards aryl bromides with electron-withdrawing groups. The catalyst was active across a broad scope of electron-donating and high-withdrawing aryl bromides with the highest activity shown for weak electron-withdrawing groups. The catalyst also showed good activity across a range of boronic acids and pinacol esters with even boronic acids featuring strong electron-withdrawing groups showing some activity. The catalyst was also a capable catalyst for the cross-coupling of aryl chlorides and phenylboronic acid. This more challenging reaction requires slightly elevated temperatures over a longer timescale but is still considered mild compared to similar examples in the literature.