Enolizable Ketones as Activators of Palladium(II) Precatalysts in Amine Arylation Reactions

Abstract

Enolizable ketones have been identified as effective activators for palladium(II) precatalysts in the coupling of aryl bromides and aniline. N-arylation reactions catalyzed by [(DTBNpP)PdCl 2 ] 2 (DTBNpP = (bis(tert-butyl)neopentylphosphine) and PEPPSI-IPr precatalysts are activated by the addition of acetone, mesityl oxide, and 3-pentanone. 3-Pentanone was the most effective activator. Mechanistic studies show that acetone, 3-pentanone, and mesityl oxide reduce [(DTBNpP)PdCl 2 ] 2 in the presence of NaO-t-Bu to Pd 0 (DTBNpP) 2 .

LPdCl2(amine) complexes supported by terphenyl phosphanes: applications in aryl amination reactions

“…1–3). The Pd–N bond lengths (2.133(2) Å for 1b , 2.1243(16) Å for 2a and 2.1199(18) Å for 3a ) are well within the range of 2.109–2.137 Å found for trans -(NHC)PdCl 2 (amine) complexes with pyridine 9 a ,21 and morpholine 18 ligands, and are also comparable to those reported for the few Pd-PEPPSI-PR 3 derivatives described so far, that is 2.24 Å for [(PPh 3 )PdCl 2 (pyridine)], 14 a 2.135 Å for [(TNpP)PdCl 2 (3-Cl-pyridine)] 13 (TNpP = trisneopentyl phosphane) and 2.168 Å for [(CAP)PdCl 2 (pyridine)]. 14 b Moreover, the Pd–P bond in complex 3a (2.261(6) Å is somewhat longer than in complexes 1b and 2a ( ca.…”

“…Recently, Shaughnessy and co-workers have described that enolizable ketones are valuable reducing additives for Pd( ii ) precatalysts in aryl amination reactions. 13 Accordingly, the catalytic activity of 3a was examined, at room temperature, in the presence of 8 mol% of two different enolizable ketones, acetone and 2-butanone. Gratifyingly, both additives facilitated the activation of 3a at room temperature and complete conversions were observed to the coupling product (Table 1, entries 7 and 8).…”

“…Considering the excellent performance of the PEPPSI-precatalysts in a wide range of cross-coupling reactions, it is somewhat surprising that the PEPPSI platform has scarcely been tested with tertiary phosphanes, typically the ligand of choice in Pd catalysis. In a recent report, Shaughnessy and co-workers 13 have compared the catalytic activity of two Pd-PEPPSI complexes supported by neopentylsubstituted phosphane with those of the halide-bridged phosphane palladium derivatives [(PR 3 )PdCl 2 ] 2 in C–N cross-coupling reactions. Moreover, the group of Nolan have described the preparations of PR 3 -Pd-PEPPSI with PPh 3 , 14 a SPhos 14 a and 1,4,7-triaza-9-phosphatricyclo[5.3.2.1]tridecane (CAP).…”

Copper and palladium bimetallic sub-nanoparticles were stabilized on modified polyaniline materials as an efficient catalyst to promote C–C coupling reactions in aqueous solution

“…Generally speaking, the material is relatively stable before 186 °C, so the Cu/Pd@Mod-PANI-3OH material is suitable for most organic synthesis reactions. In addition, 13 C CP-MAS-NMR spectra of the Cu/Pd@Mod-PANI-3OH material also confirmed a change in the carbon skeleton during the preparation process (Fig. S6 †).…”

“…Recent studies have shown that catalyst preformation strategies and the confined coordination of metals can prevent the agglomeration of metal particles to some extent and improve the catalytic activity of metals. [10][11][12][13] However, most of the currently reported catalytic systems still require the use of toxic solvents, inert gas protection, or the addition of promoters. [14][15][16] The above reaction conditions violate the fundamental principles of green chemistry.…”