Cellulose Functionalized with Amine Bidentate Ligand: Synthesis and Use as A Polymeric Support for Palladium Catalysts
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Date
2021-02-09
Authors
Nazem Ghaleb Ali, Oraib
Journal Title
Journal ISSN
Volume Title
Publisher
An Najah National University
Abstract
Two novel polymeric palladium supported catalysts were prepared and evaluated in the oxidation of alkene and ketone. The obtained results showed that, the catalysts could be used in a lab scale or commercial scale to produce α-hydroxy ketones form ketones and ketones form terminal alkenes. The polymeric material was prepared by condensation reaction of an oxidized cellulose (cellulose di-aldehyde) and 2-(2-pyridyl)ethylamine to produce cell-imine-pyridyl. Oxidized cellulose was prepared by oxidation of cellulose using sodium periodate. The polymer was characterized by FT-IR spectroscopy. The polymers then reacted with a solution of Li2PdCl4 in acetonitrile to prepare the target polymeric palladium supported catalyst (cell-pyridyl-Pd(II)).
A second polymeric palladium supported (cell-picolyl-Pd(II)) catalyst was prepared in the same manner except that 2-picolylamine was used in the place of 2-(2-pyridyl)ethylamine. Hydroxylation of ketone catalyzed with cell-pyridyl-Pd(II) and cell-picolyl-Pd(II) produced α-hydroxy ketone in moderate to excellent yield, while the oxidation of terminal alkene produced methyl ketone in moderate yield. So, both polymeric supported catalysts showed good to excellent efficiency. To enhance the solubility of the reactant, a polar aprotic solvent was chosen for the oxidation reactions in the presence of CuCl2 as a Pd(0) re-oxidant and in the presence of an acid to enhance the tautomerization of ketone to enol since the oxidation occurs on enol functional group, and the tautomerization of enol back to ketone which occurs during the oxidation of alkenes. The oxidation reactions were performed at room temperature.