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Dialkylterphenyl Phosphine‐Based Palladium Precatalysts for Efficient Aryl Amination of N ‐Nucleophiles
Author(s) -
Rama Raquel J.,
Maya Celia,
Nicasio M. Carmen
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903279
Subject(s) - amination , chemistry , denticity , nucleophile , aryl , cationic polymerization , ligand (biochemistry) , medicinal chemistry , phosphine , palladium , catalysis , terphenyl , alkyl , organic chemistry , polymer chemistry , crystal structure , biochemistry , receptor
Abstract A series of 2‐aminobiphenyl palladacycles supported by dialkylterphenyl phosphines, PR 2 Ar′ (R=Me, Et, i Pr, Cyp (cyclopentyl), Ar′=Ar Dipp2 , Ar Xyl2f , Dipp (2,6‐C6H3‐(2,6‐C6H3‐(CHMe2)2)2), Xyl=xylyl) have been prepared and structurally characterized. Neutral palladacycles were obtained with less bulky terphenyl phosphines (i.e., Me and Et substituents) whereas the largest phosphines provided cationic palladacycles in which the phosphines adopted a bidentate hemilabile k 1 ‐P,η 1 ‐C arene coordination mode. The influence of the ligand structure on the catalytic performance of these Pd precatalysts was evaluated in aryl amination reactions. Cationic complexes bearing the phosphines P i Pr 2 Ar Xyl2 and PCyp 2 Ar Xyl2 were the most active of the series. These precatalysts have demonstrated a high versatility and efficiency in the coupling of a variety of nitrogen nucleophiles, including secondary amines, alkyl amines, anilines, and indoles, with electronically deactivated and ortho ‐substituted aryl chlorides at low catalyst loadings (0.25–0.75 mol % Pd) and without excess ligand.