We describe the implementation of a system of immobilised enzymes for H-driven NADH recycling coupled to a selective biotransformation to enable H-driven biocatalysis in flow. This approach represents a platform that can be optimised for a wide range of hydrogenation steps and is shown here for enantioselective ketone reduction and reductive amination.
The high selectivity of biocatalysis offers a valuable method for greener, more efficient production of enantiopure molecules. Operating immobilised enzymes in flow reactors can improve the productivity and handling of biocatalysts, and using H2 gas to drive redox enzymes bridges the gap to more traditional metal‐catalysed hydrogenation chemistry. Herein, we describe examples of H2‐driven heterogeneous biocatalysis in flow employing enzymes immobilised on a carbon nanotube column, achieving near‐quantitative conversion in <5 min residence time. Cofactor recycling is carried out in‐situ using H2 gas as a clean reductant, in a completely atom‐efficient process. The flow system is demonstrated for cofactor conversion, reductive amination and ketone reduction, and then extended to biocatalytic deuteration for the selective production of isotopically labelled chemicals.
Lithium bis(oxalate)borate, LiB(C 2 O 4 ) 2 (LiBOB), is one of the most important electrolyte additives for Li-ion batteries (LIBs) due to its numerous advantages such as thermal stability, good solubility in organic solvents, high conductivity, and low cost as well as providing safer operations with superior electrochemical performance compared to conventional electrolyte combinations. However, the use of LiBOB is limited due to slight instability issues under ambient conditions that might require extra purification steps and might result in poorer performances in real systems. Here, we address some of these issues and report the high purity water free LiBOB synthesized with fewer processing steps employing lithium carbonate, oxalic acid, and boric acid as lowcost starting materials, and via ceramic processing methods under protective atmosphere. The physical and chemical characterizations of both anhydrous and monohydrate phases are performed with X-ray powder diffraction (XRPD), Fourier-transform infra-red spectroscopy (FTIR), Raman spectroscopy and scanning electron microscopy (SEM) analyses to determine the degree of the purity and the formation of impurities like LiBOB.H 2 O, HBO 2 and Li 2 C 2 O 4 as a result of the aging investigations performed. Differential thermal analysis (DTA) is applied to determine the optimum synthesis conditions for anhydrous LiBOB and to analyze the water loss and the decomposition of LiBOB.H 2 O. Aging experiments with the water free LiBOB are carried out to evaluate the effect of humidity in the phase changes and resulting impurities under various conditions. The detrimental effect of even slightest humidity conditions is shown, and protective measures during and after the synthesis of LiBOB are discussed. Anhydrous LiBOB could be widely used as an electrolyte additive to improve the overall electrochemical performances for LIBs through development of a protective solid electrolyte interphase (SEI) on the surface of high voltage cathodes and bringing about superior electrochemical properties with increased cycling stability, rate capability and coulombic efficiency, if synthesized, purified, and handled properly before use in real electrochemical systems.
Heterogeneous biocatalytic hydrogenation is an attractive strategy for clean, enantioselective C=X reduction. This approach relies on enzymes powered by H2-driven NADH recycling. Commercially available carbon-supported metal (metal/C) catalysts are investigated...
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