Branched Tertiary Amines from Aldehydes and α‐Olefins by Combined Multiphase Tandem Reactions

Abstract

This study presents the transformation of olefins to branched amines by combining a hydroformylation/aldol condensation tandem reaction with the reductive amination in a combined multiphase system that can be recycled 9 times. The products are branched amines that are precursors for surfactants. Since the multiphase hydrofomylation/aldol condensation system has already been studied, the first step was to develop the partial hydrogenation of unsaturated aldehydes together with a subsequent reductive amination. The rhodium/phosphine catalyst is immobilized in a polar polyethylene phase which separates from the product phase after the reaction. Reaction and catalyst recycling are demonstrated by the conversion of the C 14 -aldehyde 2pentylnonenal with the dimethylamine surrogate dimethylammonium dimethylcarbamate to the corresponding tertiary amine with yields up to 88 % and an average rhodium leaching of less than 0.1 % per recycling run. Furthermore, the positive influence of a Bronsted acid and carbon monoxide on the selectivity are discussed. Finally, the two PEG based systems have been merged in one recycling approach, by using the product phase of the hydroformylation aldol condensation reaction for the reductive amination reaction. The yields are stable during a nine recycling runs and the leaching low with 0.09 % over the two recycling stages.

Recycling of a thermoresponsive “catalyst pill”: separation of a molecular catalyst in solid ethylene carbonate in various reactions

“…Besides the hydroformylation, the hydrogenation of C 14 aldol products was tested, to investigate the reaction scope of this recycling method. 2-Pentylnon-2-enal (C 14 aldol product) was synthesized from heptanal according to a literature procedure reported by Vorholt et al 33 During the hydrogenation, a saturated aldol product in which only the double bond is hydrogenated (2-pentylnonanal) and the saturated alcohol after a subsequent hydrogenation of the aldehyde (2-pentylnonanol) are formed (reaction scheme, Table 3). This group of hydrogenated aldol products can be used in the production of surfactants, as plasticizer alcohols or in further chemical processes.…”

“…This effect was observed by Vorholt et al previously. 33 By applying vacuum to the catalyst phase at 60 °C after the third and fifth run, the CO was (partially) removed and the hydrogenation showed significantly better conversions increasing from 10% in run 1 to 63% in run 6. Additionally, the remaining nonanal from the previous run was also partly hydrogenated to nonanol during the reaction.…”

“…The synthesis of the C 14 aldol product was carried out according to the literature of Vorholt et al 33…”

Stable and Continuous Production of Amines via Reductive Amination in a Green Switchable Solvent System with Efficient Water Removal

“…This effect of carbon monoxide on the suppression of alcohol formation has already been observed in the literature. 2,6 Given that the CO addition had a much more significant influence than a reduction of catalyst concentration, it can be concluded that the CO does not act by partially deactivating the catalyst but rather by changing the catalyst species, which can also be observed by the color change of the catalyst solution from red (without CO) to yellow (with CO); see SI for photos.…”

“…Aliphatic amines are valuable products in the chemical industry, finding various applications such as in pharmaceuticals, surfactants, and agrochemicals. , One efficient way of producing amines is catalytic reductive amination (RA), in which amines are alkylated using aldehydes or ketones, yielding the desired amine. RA proceeds via an initial condensation and final catalytic reduction of the intermediate enamine or imine.…”