No abstract

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.

Tall Oil Fatty Acids, a low value side product from the paper industry containing mainly oleic and linoleic acids, are used for producing the polyester precursor, dimethyl 1,19-nonadecanedioate by methoxycarbonylation in the presence of [Pd 2 (dba) 3 ], 1,2-bis(ditertiarybutylphosphinomethyl)benzene and methanesulfonic acid in methanol. The methoxycarbonylation of methyl linoleate has been used to identify other products formed and approaches to their minimisation have been developed. It has also been used for the production of trimethyl heptadecanetricarboxylates. Finally, conjugated unsaturated esters of different chain length (up to 16 C atoms), some of them available from plant oils, are subjected to methoxycarbonylation to give α,ω-diesters.

The reaction of long chain alkenes with CO and aniline in the presence of palladium complexes of 1,2-bis-(ditertbutylphosphinomethyl)benzene produces amides with high linear selectivity, with much higher rates and catalyst stability when 2-naphthol and sodium or potassium iodide are added. Unsaturated esters including methyl 10-undecenoate from castor oil give α,ω-ester amides, whilst reactions in THF give N-phenylpyrrolidine.

Catalyst recycling is the key toward the sustainable application of homogeneously catalyzed reactions whereby integrated processes with selective product crystallization allow high selectivity under mild conditions and subsequent purification of the product without the need for any auxiliary. In this work, we develop and implement a five-step strategy toward selective product crystallization as a tool for recycling of a homogeneous catalyst using the example model reaction of methoxycarbonylation of methyl-10-undecenoate using commercially available catalyst and ligand. The strategy includes targeted investigations on the reaction regarding the stability and productivity of the catalyst but also on the crystallization, regarding catalyst leaching, product purity, and recovery, to finally develop an integrated process. Implementation of this target-oriented approach allows for increasing catalyst productivity to a cumulated turnover number ∑TON 4600 after five recycling runs and obtaining a recovery of isolated product of 82% with 98% purity of the desired linear diester.

The bidentate phosphine ligand 1,2-bis(di-tert-butylphosphinomethyl)benzene (1,2-DTBPMB) has been reported over the years as being one of, if not the, best ligands for achieving the alkoxycarbonylation of various unsaturated compounds. Bonded to palladium, the ligand provides the basis for the first step in the commercial (Alpha) production of methyl methacrylate as well as very high selectivity to linear esters and acids from terminal or internal double bonds. The present review is an overview covering the literature dealing with the 1,2-DTBPMB ligand: from its first reference, its catalysis, including the alkoxycarbonylation reaction and its mechanism, its isomerization abilities including the highly selective isomerizing methoxycarbonylation, other reactions such as cross-coupling, recycling approaches, and the development of improved, modified ligands, in which some tert-butyl ligands are replaced by 2-pyridyl moieties and which show exceptional rates for carbonylation reactions at low temperatures.

For many years, the efficient use of resources has been a major and permanent challenge for the chemical industry. The implementation of alternative resources such as renewables and carbon dioxide has been a subject of considerable discussion, but also the more efficient use of long known bulk chemicals is of great interest. Among them, 1,3‐dienes such as 1,3‐butadiene from the C4 cut of the naphtha cracker as well as isoprene, piperylene and cyclopentadiene from the corresponding C5 section are important substrates. These dienes are presently employed in various markets, with the greatest importance being in the production of polymers and copolymers. However, homogeneous transition metal catalysis has proven to be a versatile tool to functionalize these important 1,3‐dienes to low molecular weight fine chemicals by introducing, for example, nitrogen, oxygen or silicon. Hence, an upgraded use of the corresponding products as agrochemicals, pharmaceuticals, fragrances or special detergents is close at hand. The main approaches in the topic of homogeneous functionalization reactions of the industrially relevant 1,3‐dienes will be summarized and discussed within the present article. Besides that, novel applications including renewable 1,3‐dienes, for example β‐myrcene and β‐farnesene, as well as the application of CO2 in telomerization, will be critically discussed.

Long-term applications of cyclodextrins in the aqueous biphasic hydroformylation of higher olefins with high selectivities and simultaneous catalyst recycling.