A chitosan-supported ferrocenylimine palladacycle complex is shown to be an efficient catalyst for the Heck arylation.

First, 1.0G similar to 5.0G polyamidoamine dendrimers (PAMAM) were synthesized by divergent approach. Then the PAMAM were modified with salicylaldehyde by the dehydration condensation reaction of amino and aldehyde, and the Schiff base ligands (PAMAMSA) were prepared successfully. Finally, a series of PAMAMSA palladium complexes were synthesized by the reaction of Schiff base with Li2PdCl4 in methanol. The structures and components of PAMAMSA-Pd were confirmed by the characterization of FT-IR, elemental analysis and TG-DSC. Using PAMAMSA-Pd as catalyst precursor, the catalytic performances were evaluated in the Heck cross-coupling of iodobenzene (or its derivatives) with acrylic acid in neat water medium. The dendrimer catalyst showed higher activity comparing to PdCl2. The 1.0G PAMAMSA-Pd and 5.0G PAMAMSA-Pd were found to have the higher activity in the Heck reaction.

Chitosan-ferrocenylimine palladacycle complex (CS-Fe-Pd) was synthesized in a simple way and characterized by FT-IR, XRD, XPS and TG-DSC. Using CS-Fe-Pd as catalyst, it showed a highly catalytic activity and stereoselectivity to the coupling product in Heck reaction about the arylation of conjugate alkene with aryl halide. This chitosan-supported ferrocenylimine palladacycle catalyst can be recovered easily and reused at least for four cycles with high yield.

Dendritic poly(amidoamine)(PAMAM)-salicylidene salen palladium complex of the first generation (PAMAMSAPd) was synthesized and characterized by elemental analysis,FT-IR,UV-vis,Fluorescence spectra and NMR. It was evaluated as catalyst precursor in the Heck cross-coupling of iodobenzene (or its derivatives) and conjugate alkenes. For the cross-coupling reaction of iodobenzene with acrylic acid,the optimal condition was established as follows: 10mmol PhI,nPhI: nAA: nEt3N=1∶1.5∶2.5,3.0×10-3g PAMAMSAPd,4mL DMF and 100℃ reaction temperature in the inert ambience. Under the above reaction condition,the yield of cinnamate can reach 96.5% at 90min reaction time. This dendimer complex was a phosphine-free,highly efficient and stable dendrimer catalyst for Heck reaction. In addition,this dendrimer catalyst could be used at least for four times without significant loss of yield.