Hydrocarboxylation of olefins using an amphiphilic palladium catalyst, activity and recycling properties: NMR identification of some reaction intermediates

The high solubility in acidic solutions of N-bis(N′,N′-diethyl-2-aminoethyl)-4-aminomethylphenyl-diphenylphosphine (N3P) make it a suitable candidate for study and comparison to the more commonly studied trisulfonated triphenylphosphine (TPPTS) ligand in the palladium catalysed aqueous hydrocarboxylation reaction. The catalyst employing N3P shows an inverted regioselectivity compared to the TPPTS system. Non-coordinating anions give the best results in terms of activity and stability of the catalyst. Due to N3P amphiphilic character and contrary to sulfonated phosphines reaction, it is possible to recycle the catalyst, both by extracting the substrate and by extracting the catalyst into an organic solvent. The hydrocarboxylation of styrene, 1-octene and 4-penteneoic acid demonstrates that the reaction rate is strongly dependent on the solubility of the substrates. Using the water-soluble 3-buten-1-ol as substrate, two palladium zerovalent complexes, two palladium hydrides, one acyl and one alkyl complexes were identified by means of NMR and IR.

Graphical abstractThe aqueous phase hydrocarboxylation of styrene, 1-octene and 4-penteneoic acid using a palladium catalyst with the amphiphilic phosphine N3P as ligand, demonstrates that the reaction rate is strongly dependent on the solubility of the substrates. The catalyst employing N3P also shows an inverted regioselectivity compared to the TPPTS system. Due to N3P amphiphilic character, it is possible to recycle the catalyst, both by extracting the substrate and by extracting the catalyst into an organic solvent. Employing the water-soluble 3-buten-1-ol as substrate, several reaction intermediates were identified by means of NMR and IR. Figure optionsDownload full-size imageDownload as PowerPoint slide