Iron (II) P-NH-N-P Catalyst for the Transfer Hydrogenation of Ketones in Water Employing Sodium Formateas the Hydride Source

publication · 5 years ago
Iron is a cheap and abundant metal which has been shown to be catalytically active for the transfer ph ph -1 8,4 hydrogenation (TH) of ketones in an enantioselective manner when combined with suitably H designed ligands. Our groups current batch reaction process uses isopropanol as both the solvent (N,91),) and hydride source allowing equilibrium between the ketone and product alcohol to be quickly ,,,e\ reached at 80 % conversion.' The goal of this project is to replace the solvent by water allowing the III Ph use of sodium formate as the hydride source. As the reaction proceeds sodium formate is 2. 2 convened into carbon dioxide, which is flushed out of the reaction flask to help drive the hydrogenation of ketones to completion.2 In this biphasic reaction, it was postulated that the transfer of the aqueous hydride source was rate-limiting due to the inability of the charged sodium formate to enter the non-polar acetophenone/catalyst layer by simple stirring and temperature control. Therefore a variety of phase-transfer catalysts (PTCs) were tested in order to increase the concentration of the sodium formate in the organic layer, leading to greater percent conversions. Although, it was observed that PTCs containing halogen counteranions decrease catalytic activity, presumably by reversibly binding to the active catalyst. An optimization of the reaction conditions was performed with acetophenone as the model substrate to then test a variety of more water-soluble ketone substrates.
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