Synthesis and evaluation of phosphine–N ligands in transition metal-catalysed CC bond forming reactions

A series of phosphino-imine and the corresponding phosphino-amine P,NR ligands (R = alkyl, aryl) was synthesised from the commercially available starting material 2-(diphenylphosphino)benzaldehyde, including P,N bi-, tri- and tetradentate imine ligands, their secondary amine analogues, and also the methylated tertiary amine equivalents. As an extension, some P,NPPh2 and P,NPCy2 derivatives were also prepared from the same starting material. All of these ligands were successfully applied in catalytic reactions (Heck, cross-coupling and hydroformylation), and benchmarked against traditional ligands with satisfying results. While providing catalyst systems that were stable and generally acceptably active in comparison with the benchmarks, the Pd–ligand catalyst systems of this study were found to be especially active in Stille reactions.

Graphical abstractVarious readily available P–N ligands with substantial variety at N (oxidation state and functionalisation) were prepared and successfully applied in several Pd-catalysed transformations.Figure optionsDownload full-size imageDownload as PowerPoint slide