Merging High-Pressure Syngas Metal Catalysis and Biocatalysis in Tandem One-Pot Processes for the Synthesis of Non-chiral and Chiral Alcohols from Alkenes in Water.

While simultaneously proceeding reactions are among the most fascinating features of biosynthesis, this concept of tandem processes also offers high potential in the chemical industry in terms of less waste production and improved process efficiency and sustainability. Although examples of one-pot chemoenzymatic syntheses exist, the combination of completely different reaction types is rare. In this work, we demonstrate that extreme "antipodes" of the "worlds of catalysis" such as syngas-based high-pressure hydroformylation and biocatalyzed reduction can be combined within a tandem­type one-pot process in water, which both play an outstanding role as individual reactions. No significant deactivation was found for either the biocatalyst or the chemocatalyst. A proof­of­concept for the one-pot process starting from 1-octene was established with >99% conversion and 80% isolated yield of the desired alcohol isomers. All necessary components for hydroformylation and biocatalysis were added to the reactor from the beginning. This concept has been extended to chiral products by conducting the hydroformylation of styrene and an enzymatic dynamic kinetic resolution in a tandem mode, leading to an excellent conversion of >99% and an enantiomeric ratio of 91:9 to (S)­2-phenylpropanol. The overall process runs in water under mild and energy-saving conditions, without any need for intermediate isolation.

Branched Tertiary Amines from Aldehydes and α-Olefins by Combined Multiphase Tandem Reactions.

This study presents the transformation of olefins to branched amines by combining a hydroformylation/aldol condensation tandem reaction with the reductive amination in a combined multiphase system that can be recycled 9 times. The products are branched amines that are precursors for surfactants. Since the multiphase hydrofomylation/aldol condensation system has already been studied, the first step was to develop the partial hydrogenation of unsaturated aldehydes together with a subsequent reductive amination. The rhodium/phosphine catalyst is immobilized in a polar polyethylene phase which separates from the product phase after the reaction. Reaction and catalyst recycling are demonstrated by the conversion of the C14 -aldehyde 2-pentylnonenal with the dimethylamine surrogate dimethylammonium dimethylcarbamate to the corresponding tertiary amine with yields up to 88 % and an average rhodium leaching of less than 0.1 % per recycling run. Furthermore, the positive influence of a Bronsted acid and carbon monoxide on the selectivity are discussed. Finally, the two PEG based systems have been merged in one recycling approach, by using the product phase of the hydroformylation aldol condensation reaction for the reductive amination reaction. The yields are stable during a nine recycling runs and the leaching low with 0.09 % over the two recycling stages.

Direct Conversion of Syngas to Higher Alcohols via Tandem Integration of Fischer-Tropsch Synthesis and Reductive Hydroformylation.

The selective conversion of syngas to higher alcohols is an attractive albeit elusive route in the quest for effective production of chemicals from alternative carbon resources. We report the tandem integration of solid cobalt Fischer-Tropsch and molecular hydroformylation catalysts in a one-pot slurry-phase process. Unprecedented selectivities (>50 wt %) to C2+ alcohols are achieved at CO conversion levels >70 %, alongside negligible CO2 side-production. The efficient overall transformation is enabled by catalyst engineering, bridging gaps in operation temperature and intrinsic selectivity which have classically precluded integration of these reactions in a single conversion step. Swift capture of 1-olefin Fischer-Tropsch primary products by the molecular hydroformylation catalyst, presumably within the pores of the solid catalyst is key for high alcohol selectivity. The results underscore that controlled cooperation between solid aggregate and soluble molecular metal catalysts, which pertain to traditionally dichotomic realms of heterogeneous and homogeneous catalysis, is a promising blueprint toward selective conversion processes.

Auto-Tandem Catalytic Reductive Hydroformylation in a CO2-Switchable Solvent System.

Upgradation of olefin-enriched Fischer-Tropsch cuts by the synthesis of alcohols leads to drop-in-capable biosynthetic fuels with low carbon emissions. As an alternative to the conventional two-step production of long-chain alcohols, tandem catalytic systems improve the energy and resource efficiency. Herein, we present an auto-tandem catalytic system for the production of alcohols from olefin-paraffin mixtures. By utilization of a tertiary alkanolamine as the ligand as well as the switchable component in the solvent system, a lean reaction system capable of catalyst recycling was developed. The system was characterized with regard to the switchable solvent separation approach and reaction parameters, resulting in alcohol yields of up to 99.5% and turnover frequencies of up to 764 h-1. By recycling the catalyst in 10 consecutive reactions, a total turnover number of 2810 was achieved.

Commercial Cu2 Cr2 O5 Decorated with Iron Carbide Nanoparticles as a Multifunctional Catalyst for Magnetically Induced Continuous-Flow Hydrogenation of Aromatic Ketones.

Copper chromite is decorated with iron carbide nanoparticles, producing a magnetically activatable multifunctional catalytic system. This system (ICNPs@Cu2 Cr2 O5 ) can reduce aromatic ketones to aromatic alcohols when exposed to magnetic induction. Under magnetic excitation, the ICNPs generate locally confined hot spots, selectively activating the Cu2 Cr2 O5 surface while the global temperature remains low (≈80 °C). The catalyst selectively hydrogenates a scope of benzylic and non-benzylic ketones under mild conditions (3 bar H2 , heptane), while ICNPs@Cu2 Cr2 O5 or Cu2 Cr2 O5 are inactive when the same global temperature is adjusted by conventional heating. A flow reactor is presented that allows the use of magnetic induction for continuous-flow hydrogenation at elevated pressure. The excellent catalytic properties of ICNPs@Cu2 Cr2 O5 for the hydrogenation of biomass-derived furfuralacetone are conserved for at least 17 h on stream, demonstrating for the first time the application of a magnetically heated catalyst to a continuously operated hydrogenation reaction in the liquid phase.

Green Process Design for Reductive Hydroformylation of Renewable Olefin Cuts for Drop-In Diesel Fuels.

CO2 -neutral fuels are a way to cleaner and more sustainable mobility. Utilization of bio-syngas via Fischer-Tropsch (FT) synthesis represents an interesting route for the production of tailormade biofuels. Recent developments in FT catalyst research led to olefin-enriched products, enabling the synthesis of alcohol-enriched fuels by reductive hydroformylation of the C=C bond. Several alcohols have already proven to be suitable fuel additives with favorable combustion behavior. Here, a hydroformylation-hydrogenation sequence of FT-olefin-paraffin mixtures was investigated as a potential route to alcohols. A liquid-liquid biphasic system with a rhodium/3,3',3''-phosphanetriyltris(benzenesulfonic acid) trisodium salt (TPPTS) catalyst system was chosen for effective catalyst recycling. After optimizing reaction conditions with a model substrate consisting of 1-octene and n-heptane the conversion of an actual olefin-containing C5 -C10  FT product fraction to alcohols in continuously operated processes for 37 h was achieved with a total turnover number of 23679.

Thermomorphic Multiphase Systems: Switchable Solvent Mixtures for the Recovery of Homogeneous Catalysts in Batch and Flow Processes.

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.

From Carboxytelomerization of 1,3-Butadiene to Linear α,ω-C10 -Diester Combinatoric Approaches for an Efficient Synthetic Route.

Two novel reaction pathways were tested to synthesize the linear α,ω-C10 -diester exclusively from three basic reagents: 1,3-butadiene, carbon monoxide and methanol. Therefore, carboxytelomerization of 1,3-butadiene and methanol was merged with methoxycarbonylation in two different ways to obtain highly linear C10 -diester. Through a palladium-based and -assisted tandem catalytic system, 22 % yield of the desired C10 -diester was obtained without isolating the intermediates. Subsequently, the limitations of the novel assisted tandem catalytic concept were uncovered and based on that, a two-step reaction regime was established. By optimization of the carboxytelomerization, the C9 -monoester as intermediate could be formed in nearly quantitative yields and excellent linearity. In a second reaction step, the isolated monoester was successfully converted by methoxycarbonylation into the desired linear C10 -diester in overall yields up to 84 %.

Overcoming Phase-Transfer Limitations in the Conversion of Lipophilic Oleo Compounds in Aqueous Media-A Thermomorphic Approach.

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.

Direct Synthesis of an α,ω-Diester from 2,7-Octadienol as Bulk Feedstock in Three Tandem Catalytic Steps.

A new tandem catalytic process was designed and developed as a tool for the direct conversion of the widely available feedstock 2,7-octadienol into an α,ω-diester. This innovative auto-tandem catalysis is atom efficient and consists of three consecutive palladium-catalysed reactions: ether formation, ether carbonylation and alkoxycarbonylation. By using the design of experiments (DoE) approach, significant parameters were determined and the yield of the desired α,ω-diester was optimised. Model substrates allowed deeper insight into the progress of the reaction to be gained and, as a result, the reaction sequence was uncovered. Furthermore, by simply applying other ligands, a different reaction path was followed, allowing other, new tandem catalytic sequences to be explored and enabling new compounds to be obtained.