Dialkylterphenyl Phosphine‐Based Palladium Precatalysts for Efficient Aryl Amination of N‐Nucleophiles

Abstract

Aseries of 2-aminobiphenyl palladacycles supported by dialkylterphenyl phosphines, PR 2 Ar' (R = Me, Et, iPr, Cyp (cyclopentyl), Ar' = Ar Dipp2 ,A r Xyl2f ,D ipp (2,6-C6H3-(2,6-C6H3-(CHMe2)2)2), Xyl = xylyl) have been prepareda nd structurally characterized. Neutral palladacycles were obtained with less bulky terphenyl phosphines (i.e.,M ea nd Et substituents) whereas the largest phosphines provided cationic palladacycles in whicht he phosphines adopted ab identate hemilabile k 1 -P,h 1 -C arene coordination mode.T he influence of the ligand structure on the catalytic performance of these Pd precatalysts was evaluated in aryl aminationr eactions.C ationicc omplexes bearing the phosphines Pi-Pr 2 Ar Xyl2 andP Cyp 2 Ar Xyl2 weret he most active of the series. Thesep recatalysts have demonstrated ah igh versatility and efficiency in the coupling of av ariety of nitrogen nucleophiles, including secondary amines, alkyl amines,a nilines, and indoles, with electronically deactivated and ortho-substituted aryl chloridesa tl ow catalyst loadings (0.25-0.75 mol % Pd) and withoutexcess ligand.[a] R.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.Scheme2.Synthesis of complexes 2a and 2b.Scheme3.Generalsynthesis of complexes 3d and 3e.

N-substituted aminobiphenyl palladacycles stabilized by dialkylterphenyl phosphanes: Preparation and applications in C N cross-coupling reactions

“…Very recently, we have reported on the preparation of 2-aminobiphenyl palladacycles supported by a variety of dialkylterphenyl phosphane ligands developed in our research group, [13] and demonstrated their competence as precatalysts in a variety of C-N cross-coupling reactions. [14] This work extends these studies to N-substituted 2aminobiphenyl palladacycle analogues. Herein, we described the synthesis and the structural characterization of a series of N-methyl-and N-phenyl-substituted 2aminobiphenyl palladacycle bearing terphenyl phosphanes.…”

“…40 ppm to higher frequency relative to the free phosphane. Comparison with NMR data found for other transition metals terphenyl phosphanes complexes, including palladium, [13,14,18] suggests monodentate coordination of phosphane in 1•L1 and 2•L1. Hence, it is safe to assume that the mesylate anion is coordinated to the metal center in these two palladacycles.…”

Important Role of NH-Carbazole in Aryl Amination Reactions Catalyzed by 2-Aminobiphenyl Palladacycles

“…Recently, we examined the behavior of a family of dialkylterphenyl phosphines − in Pd-catalyzed aryl amination reactions using 2-aminobiphenyl-derived palladacycles as precatalysts. , We found that the cationic palladacycle with the sterically demanding phosphine PCyp 2 Ar Xyl2 , P1 (Scheme ), displayed excellent performance and provided a broader substrate scope in the amination of deactivated aryl chlorides with N -nucleophiles, including primary and secondary alkyl and arylamines and N -heterocycles such as indoles (Table ). To understand the reasons for the high activity and broad applicability of palladacycle P1 , we decided to investigate the mechanism of aryl amination reactions catalyzed by P1 , including the precatalyst activation step, by experiments and calculations.…”

Palladium(II) Complexes of (2,6‐Dibenzhydryl‐4‐methylphenyl)diphenyl‐phosphane: Synthesis, Structural Studies, and Catalytic Arylation of Imidazoles Under Aerobic Conditions

“…[9a-c,8e,9d] Sterically demanding phosphines are particularly interesting because they frequently exhibit air stability, intriguing metal arene interactions, and rare M•••H interactions, which are key to many metal-mediated organic transformations. [10] In this context, we recently reported the synthesis of sterically demanding mono-and bisphosphine ligands. The monophosphine ligands afforded rare [RuCl 2 (k-Pη 6 -arene)] type tethered Ru-arene complexes.…”