A smart palladium catalyst in ionic liquid for tandem processes

Abstract

New catalytic systems based on in situ and preformed palladium nanoparticles in ionic liquids (characterised by TEM) starting from palladium acetate or dipalladiumtris(dibenzylideneacetone) have been applied in the synthesis of 4-phenylbutan-2-one (II), a model compound for the preparation of fragrances. Imidazolium-based ionic liquid containing a methyl hydrogenophosphonate anion leads to an efficient Pd-catalyzed tandem coupling/reduction process, taking advantage of the multi-role of this solvent (nanoparticles stabiliser, base, hydrogen transfer agent). The influence of the mono-phosphine ligands (1-3) on the catalyst has been evaluated, showing that the ligand-free palladium system turns into the most appropriate for the formation of II using Pd(OAc)(2) as precursor. Fine-tuning conditions involved in this multi-parameter process have led us to propose a plausible mechanism based on the hydrogen transfer coming from the methyl hydrogenophosphonate anion.

Recyclable nanoscale copper(i) catalysts in ionic liquid media for selective decarboxylative C–C bond cleavage

“…organo-boron, organo-tin, organo-zinc) reagents. 6 Nowadays metal nanoparticles, such as ruthenium, [7][8][9][10][11][12][13][14][15] platinum, 16 iridium, [17][18][19] palladium, 5,[20][21][22][23][24][25][26][27][28][29][30][31] cobalt, 32 and iron, 33 have great potential for application 34 in homogeneous and heterogeneous catalysis, including hydrogenation, 7 hydrogenolysis, 35 Fischer-Tropsch reactions 32,36 and cross-coupling reactions. 4,5,21,23 Copper 37 and especially copper(I)oxide 38 nanoparticles combine the high catalytic activity of precious metals with easy availability and low cost.…”

Tuning the hydrogen donor/acceptor behavior of ionic liquids in Pd-catalyzed multi-step reactions

“…As we previously observed [23], phenylbutanone II was also generated under the reaction conditions. Selected results are collected in Table 1.…”

“…In general, IL cations are considered as non-innocent ligands in many reactions, whereas IL anions are mistakenly considered as 'spectators'. In a previous study, we investigated the reaction chemistry of palladium nanoparticles with phosphorous ligands in the ionic liquid [EMI][MeHPO 3 ] (A) [23]. We found a unique catalytic system for a one-pot multi-step process of Heck-Mizoroki reaction followed by reduction of the coupled product in a sequential way (Scheme 1) as a result of a cooperative effect between the ligand and the ionic liquid.…”

Ionic liquids in catalysis: molecular and nanometric metal systems

“…Sulphur-based compounds can also help to the immobilisation of MNPs on modified supports by sulphur functions, which avoid the leaching of molecular species, as observed in the case of PdNPs supported on modified silica, which were applied in Suzuki-Miyaura couplings and hydrogenations [41]. In this context, we were interested in the study of thioether-phosphines as stabilisers with the aim to modulate the catalytic reactivity of PdNPs, which were prepared in both, an organic solvent (THF) and ImILs (see Figure 4 for ligands structure) [42][43][44]. When…”

“…With the aim to weaken the direct interaction of thioether-phosphines with the metallic clusters and consequently to avoid their degradation, we decided to synthesise PdNPs in ILs (Scheme 5) [43,44]. We tested these PdNPs in the HeckMizoroki cross-coupling reaction (Table 1).…”