Abstract
The homogeneously catalyzed reductive amination of the long-chain aldehyde undecanal with diethylamine was performed in an aqueous microemulsion system using the non-ionic surfactant Marlophen NP8. The experiments showed that the used water-soluble rhodium/SulfoXantphos catalyst system is suitable for this reaction. The Rh-catalyzed formation of the alcohol by-product can be completely suppressed by the use of carbon monoxide with its stabilizing effect of the catalyst system. In addition to pressure and temperature, the most important parameters for the reaction performance of the reductive amination are the concentrations of reactants. Especially, the initial concentration of the aldehyde has a strong impact on the chemoselectivity, and the formation of aldol by-product due to the fact that both, the enamine condensation and the aldol condensation are equilibrium reactions.
Highlights
Reductive Amination of Undecanal in Currently, the concept of Green Chemistry is of great interest in research as well as industrial applications
We studied the reductive amination of undecanal with diethylamine (Figure 1) in an aqueous microemulsion system with the objective to couple it later with the hydroformylation to a one-pot hydroaminomethylation
The role of CO as a ligand in the rhodium complex seems to be very important here. This changes the electronic structure of the Rh-catalyst and prevents the catalytic alcohol formation
Summary
Reductive Amination of Undecanal in Currently, the concept of Green Chemistry is of great interest in research as well as industrial applications. Warner are a well-known concept for researchers in that field One of these principles describes the use of metal-catalyzed reactions instead of stoichiometric ones [1]. The most common production route for amines is the heterogeneously catalyzed hydrogenation of nitriles with low-priced metal catalysts (Ru/C, Pd/C, or Pt/Al2 O3 ) [4]. Aldehydes can be converted into amines via reductive amination In these processes, the aldehyde reacts with an amine to an imine/enamine, which can subsequently be hydrogenated with a heterogeneous catalyst e.g., Pd/C or Raney nickel [5]. The described heterogeneous methods for the synthesis of aliphatic amines show low selectivity in the hydrogenation, resulting in a mixture of primary, secondary and tertiary amines, and further side products
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