Aqueous Biphasic Hydroaminomethylation Enabled by Methylated Cyclodextrins: Sensitivity Analysis for Transfer into a Continuous Process

Abstract

Hydroaminomethylation (HAM) is a highly efficient homogeneously catalyzed autotandem reaction converting alkenes into valuable amine products with water being the only coproduct. This work reports for the first time the scale-up of the highly regioselective HAM of 1-decene with diethylamine for a potential continuous process application in a green and sustainable aqueous biphasic medium. The catalytic system Rh/SulfoXantphos and randomly methylated β-cyclodextrin (RAME-β-CD) were herein dissolved in the plain aqueous phase. The addition of cyclodextrins as a green mass transfer agent remarkably increases the reaction rate as well as the selectivity toward linear amines, but they can also support solid content precipitation in this reaction system due to up-scaling effects. Therefore, parameters such as catalyst concentration, organic volume fraction, cyclodextrin concentration, and recyclability were investigated regarding the stability and activity of the system. Especially the organic volume fraction had a decisive influence on solid content precipitation. High regio- and chemoselectivities of 35 and 82%, respectively, at nearly full conversion were achieved toward the linear product amine. The catalytic system was further recycled in batch and scaled up into a 2100 mL autoclave without loss in activity and selectivity. Finally, a continuous process concept was proposed for an extensive investigation regarding long-term stability of the catalytic system.