Optimisation of Palladium-Based Supported Liquid-Phase Catalysts in the Heck Reaction

Abstract

Heck reactions using sulphonated triphenylphosphine palladium complexes have been carried out using a supported liquid-phase catalysis system in a batch reactor. The catalyst complex is held in solution in a polar, hydrophilic film supported upon porous glass beads whilst reactants and products are restricted to a nonmiscible solvent phase. Several factors in the preparation of the supported catalyst were investigated with the aim of ensuring good assembly, distribution, and immobilisation of the catalyst complex across the surface of the beads. The thickness of the hydrophilic film upon the porous glass beads was varied. The hydrophilic nature of the ligand complex was studied using mono- and trisulphonated sodium and lithium salts of triphenylphosphine. The effects of level of catalyst loading and ligand/catalyst ratio upon leaching and activity were also examined. These factors have been examined to develop a better understanding of the catalysis occurring in supported liquid-phase systems.

A comparative study of supported aqueous- and ethylene glycol-phase catalysts in stilbene hydrogenation: Influence of the different modes of dispersion of supported liquids

“…These authors also showed that the enantioselectivity increased with the quantity of EG used and they speculated that this could be ascribed to the increasing rotational mobility of the ruthenium complex in the liquid phase. The importance of the metal complex mobility for the Heck reaction was also suggested by Mirza et al [22]. However, it should be noted again that both the groups carried out the reactions at constant total amounts of the metal complexes.…”

“…2 may intrinsically result from the different nature and behavior of the two supported liquids of water and EG over the silica surface. Figure 2 The influence of liquid loading was examined by other research groups for hydroformylation [3,[11][12][13][14][15], hydrogenation [7,8], Heck coupling [22] and alkylation [29]. For example, Delamas and co-researchers indicated that a maximum activity of Rh-SLPC-W for hydroformylation occurred before the pore volume of the support material was fully filled with water [14].…”

“…The differences between water and EG were indicated by Wan and Davis, who prepared a SLPC sample in which the active species, [Ru(BINAP-4SO 3 Na)(benzene)Cl]Cl, existed in EG supported on a controlled pore glass [22,23]. The SLPC so prepared was active for asymmetric synthesis of naproxen and the use of EG is important.…”

“…This is significant because overall reaction rates in biphasic systems are sometimes limited by low liquid-liquid interfacial areas and it is difficult to increase this area by mechanical agitation [9]. The concept of SLPC is well proven in the cases of hydroformylation [2][3][4][5][10][11][12][13][14][15][16], hydrogenation [6][7][8][17][18][19][20], Heck reactions [21][22][23][24][25][26][27][28] and alkylation [29]. Recently, it has also been reported that simultaneous use of two types of SLPC samples can give bi-functional catalyst systems, which are sometimes difficult to obtain by the use of mixtures of homogeneous or biphasic metal complex catalysts because of undesired negative interactions between the different metal complexes [19].…”

Mizoroki–Heck Reactions: Modern Solvent Systems and Reaction Techniques

“…The simple catalyst separation is an important step towards the development of environmentally friendly industrial processes. There is a wide variety of literature on Mizoroki-Heck reactions with TPPTS or related water-soluble phosphine salts 55-63 ( Figure 15.5) in aqueous organic solvents [156][157][158][159][160][161][162][163][164][165][166][167][168][169][170][171][172]. Ligand 56 was tested in various Mizoroki-Heck couplings and compared with a few other water-soluble ligands.…”