Molecular‐Weight‐Enlarged Multiple‐Pincer Ligands: Synthesis and Application in Palladium‐Catalyzed Allylic Substitution Reactions

Abstract

Three different pincer ligand systems are synthesized via nucleophilic substitution reactions of polyaromatic benzyl bromides as support molecules and phenol derivatives as ligand precursors. Retention tests using a polymeric nanofiltration membrane show moderate to good retention in THF and CH(2)Cl(2). Concentration-dependent NMR spectroscopy gives no indication for the formation of aggregates in solution. The three ligand systems are active in both the allylic alkylation and allylic amination reactions and show high selectivity towards the linear trans products. An investigation of the kinetic parameters of the allylic amination reaction show that the reaction of cinnamyl acetate with morpholine is of zero order in cinnamyl acetate and of first order in morpholine. The order in catalyst is found to be one, and the rate constant k' is determined for a reaction under standard conditions. Moreover, one of the tri(pincer)-palladium complexes is used as soluble, molecular-weight-enlarged homogeneous catalyst in continuous allylic alkylation and amination reactions. The conversion of the allylic alkylation reaches a maximum of 30 %, while a maximum conversion of 80 % is reached in the allylic amination reaction. No palladium black was formed.

Recent advances in the recycling of homogeneous catalysts using membrane separation

“…15 Nanometre-sized multiple PCP-pincer ligand systems (Fig. 15) were used in the allylic amination of cinnamyl acetate with morpholine and in the allylic alkylation of cinnamyl acetate with dimethyl malonate.…”

Carbon coated magnetic nanoparticles as supports in microwave-assisted palladium catalyzed Suzuki-Miyaura couplings

“…Seven hundred and eleven milligram (2.54 mmol) 3,5-bis(bromomethyl)phenol ( 3 ) [16] and 946 mg (5.08 mg, 2.0 equiv.) 1-mesityl-1H-imidazole ( 4 ) [17] were stirred in 5 ml MeCN at 90 ° C in a sealed tube for 1 h. After cooling down to ambient temperature the white precipitate was washed thrice with MeCN and acetone to yield 1.42 g (2.2 mmol, 86 % ) 5 as a white solid.…”

Coupling Rhodium‐Catalyzed Hydroformylation of 10‐Undecenitrile with Organic Solvent Nanofiltration: Toluene Solution versus Solvent‐Free Processes

“…Few studies have focused on the recycling of homogeneous metal catalysts by OSN in solvent‐free media (later referred to as bulk media) while some studies have dealt with the influence of the solvent on the membrane performances . Van der Gryp et al .…”

“…Many laboratory-scale studies have already established the potential of OSN for homogeneous catalyst recycling. [10][11][12][13][14][15][16][17] Upon tuning the type of membrane, [18][19][20][21][22] catalyst, [23,24] solvent [25][26][27][28][29] and operating conditions (mainly transmembrane pressure, TMP [27,30,31] and sometimes temperature [28,31,32] ), almost full catalyst rejections were obtained. Nevertheless, it must be underlined that these studies usually focused on the catalyst rejection by the membrane and paid no or very little attention to the target product extraction, which is however an absolute requirement for an industrial production process.…”