Over the past 20 years, thermomorphic multiphase systems (TMS) have been used as a versatile and elegant strategy for the recovery and recycling of homogeneous transition‐metal catalysts, in both batch‐scale experiments and continuously operated processes. TMS ensure a homogeneous reaction in a monophasic reaction mixture at reaction temperature and the recovery of the homogeneous transition‐metal catalyst through liquid–liquid separation at a lower separation temperature. This is achieved by using at least two solvents, which have a highly temperature‐sensitive miscibility gap. The suitability of commercially available solvents makes this approach highly interesting from an industrial point of view. For the first time, herein, all studies in the area of TMS are reviewed, with the aim of providing a concise and integral representation of this approach for homogeneous catalyst recovery. In addition to the discussion of examples from the literature, the thermodynamic fundamentals of the temperature‐dependent miscibility of solvents are also presented. This review also gives key indicators to compare different TMS approaches, for instance. In this way, new solvent combinations and in‐depth research, as well as improvements to existing approaches, can be addressed and promoted.

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The rhodium-BiPhePhos catalyzed hydroformylation of n-decenes, as representative long-chain olefins, was investigated in this study experimentally and theoretically. Besides hydroformylation activity, the used catalyst enables significant double bond isomerization which is an essential side reaction. Because of this property, highly selective tandem isomerization-hydroformylation reactions that convert mixtures of n-decenes with internal double bond position to the desired terminal aldehyde undecanal are possible using the Rh-BiPhePhos catalyst. Experimentally, a reaction network analysis strategy was applied to study the coupled main and side reactions separately. Subsequently, a mechanistic kinetic model based on an extended Wilkinson-mechanism was developed that includes all relevant main and side reactions. Fitting the model to the 23 well planned experiments was possible with low deviations between model and experiment, including the tandem reaction. It was found that the tandem reaction shows completely opposite dependencies regarding temperature and synthesis gas pressure compared to the conventional hydroformylation of 1-decene, which is also covered by the model. Hence, strategies for optimal reaction performance of the (tandem isomerization-)hydroformylation were developed and presented.

A new process concept has been developed for recycling transition-metal catalysts in the synthesis of moderately polar products via aqueous thermomorphic multicomponent solvent systems. This work focuses on the use of "green" solvents (1-butanol and water) in the hydroformylation of the bio-based substrate methyl 10-undecenoate. Following the successful development of a biphasic reaction system on the laboratory scale, the reaction was transferred to a continuously operated miniplant to demonstrate the robustness of this innovative recycling concept for homogenous catalysts.

A catalytic system was developed to enable the use of industrially available terpenes (e.g., β‐myrcene, β‐farnesene) in hydroaminomethylation to obtain renewable building blocks for surfactants in two steps. This homogeneously catalyzed tandem reaction includes both hydroformylation and enamine condensation steps, followed by hydrogenation. Under the optimized conditions, the Rh/1,2‐bis(diphenylphosphino)ethane catalytic system delivers products in high yields (70 %) after short reaction times (3 h) with unprecedentedly high turnover frequency (TOF) values for the hydroformylation of 1,3‐dienes of over 739 mol mol−1 h−1. This is the highest TOF reported to date for the hydroformylation of a 1,3‐diene. Furthermore, regioselectivities of 97 % and above were observed in the hydroformylation step, which is extraordinarily high for the conversion of 1,3‐dienes. The terpene‐derived amines obtained were further functionalized to quaternary ammonium compounds that were found to show surface activity quite similar to that of industrially available quaternary ammonium compounds. The hydroaminomethylation of terpenes achieves higher step efficiency than industrial means and makes use of an alternative, renewable feedstock to synthesize more environmentally friendly surfactants.