Regioselective Rhodium‐Catalyzed 1,2‐Hydroboration of Pyridines and Quinolines Enabled by the Tris(8‐quinolinyl)phosphite Ligand

• Published in: European journal of inorganic chemistry 2023-10, Vol.26 (29)
• Main Authors: Chacón‐Terán, Miguel A., Landaeta, Vanessa R., Wolf, Robert, Rodríguez‐Lugo, Rafael E.
• Format: Article
• Language: English
• Subjects: Additives; Catalysts; Chemical synthesis; Hydroboration; Inorganic chemistry; Ligands; Molecular structure; Organic compounds; Oxidation; Pyridines; Regioselectivity; Rhodium; Substrates
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202300267

A Rh(I) complex [κ 2 ( P,N )‐{P(Oquin) 3 }RhCl(PPh 3 )] ( 1 ) bearing the P,N ligand tris(8‐quinolinyl)phosphite, P(Oquin) 3 , has been synthesized and structurally characterized. The molecular structure of complex 1 shows that P(Oquin) 3 acts as a bidentate P,N chelate ligand. Reactivity studies of 1 reveal that the triphenylphosphine ligand can be replaced by Pcy 3 or removed upon oxidation with concomitant coordination of a second 8‐quinolyl unit of P(Oquin) 3 . In addition, the Rh(III) complex [RhCl 2 {OP(Oquin) 2 }] ( 3 ), resulting from treating 1 with either wet CDCl 3 or, sequentially, with HCl and water, was identified by X‐ray diffraction analysis. Complex 1 catalyzes the 1,2‐regioselective hydroboration of pyridines and quinolines, affording N ‐boryl‐1,2‐dihydropyridines (1,2‐BDHP) and N ‐boryl‐1,2‐hydroquinolines (1,2‐BDHQ) in high yield (up to >95 %) with turnover numbers (TONs) of up to 130. The system tolerates a variety of substrates of different electronic and steric nature. In comparison with other transition‐metal‐based hydroboration catalysts, this system is efficient at a low catalyst loading without the requirement of base or other additives.