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.
The first applications of aqueous
surfactant-free multiphase emulsions as reaction media for rhodium-catalyzed
hydroformylation of 1-dodecene and Suzuki coupling reaction of 1-chloro-2-nitrobenzene
and 4-chlorobenzeneboronic acid are herein reported. The reaction
systems were formulated from oil (reactant and solvent), aqueous catalyst
solution, and diethylene glycol butyl ether [C4H9(C2H4O)2OH]. We investigated these
multiphase systems with respect to reaction engineering and catalyst
recycling to evaluate their application potential for new chemical
processes based on switchable solvents. For the hydroformylation,
conversion of 23.4% after 4 h reaction time could be achieved at mild
reactions conditions of 95 °C and 15 bar syngas pressure. The
applied Rhodium-SulfoXantPhos catalyst could be successfully recycled
for four times, maintaining its very high linear-to-branched selectivity
of 99:1. For the Suzuki coupling reaction yields up to 90% were achieved
within a single run. The Pd/SPhos catalyst could be recycled three
times, but activity decreased at almost stable selectivity due to
higher ligand leaching during the separation steps.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.