Dynamic Kinetic Resolution Of Amines Research Articles

Metal-enzyme nanogel biochemical composite: An efficient platform for one-pot dynamic kinetic resolution of amines

One-pot dynamic kinetic resolution (DKR) has garnered considerable attention for its potential to generate enantiomerically pure compounds in high yields and simplifying operation. However, the challenge lies in achieving compatibility between enzymes and metals due to their distinct operating conditions. In this study, we present a novel cascade catalytic platform for the DKR of amines to address this issue. Pd nanoparticles were immobilized on lysine-decorated lipase nanogels, forming isolated metal-enzyme catalysts. The microwave-assisted one-pot DKR of amines was carried out under non-pressurized conditions at 50 °C for 5 h. The metal-enzyme nanogel biochemical composite exhibited excellent performances, with a high conversion rate of 98% and enantiomeric excess values exceeding 99%. This innovative approach demonstrates the potential of constructing a multifunctional metalloenzyme catalytic platform with a distinctive three-dimensional structure, which offers promising prospects for DKR applications.

Bottom-Up Synthesis of Multicompartmentalized Microreactors for Continuous Flow Catalysis.

The bottom-up assembly of biomimetic multicompartmentalized microreactors for use in continuous flow catalysis remains a grand challenge because of the structural instability or the absence of liquid microenvironments to host biocatalysts in the existing systems. Here, we address this challenge using a strategy that combines stepwise Pickering emulsification with interface-confined cross-linking. Our strategy allows for the fabrication of robust multicompartmentalized liquid-containing microreactors (MLMs), whose interior architectures can be exquisitely tuned in a bottom-up fashion. With this strategy, enzymes and metal catalysts can be separately confined in distinct subcompartments of MLMs for processing biocatalysis or chemo-enzymatic cascade reactions. As exemplified by the enzyme-catalyzed kinetic resolution of racemic alcohols, our systems exhibit a durability of 2000 h with 99% enantioselectivity. Another Pd-enzyme-cocatalyzed dynamic kinetic resolution of amines further demonstrates the versatility and long-term operational stability of our MLMs in continuous flow cascade catalysis. This study opens up a new way to design efficient biomimetic multicompartmental microreactors for practical applications.

Synthesis and characterization of a magnetic hybrid catalyst containing lipase and palladium and its application on the dynamic kinetic resolution of amines

Recent papers estimates that about 40 % of drugs present chiral amines in their structure and their synthesis in a sustainable and cost-competitive way is still a challenge for the industry. Kinetic resolution is one of the most applied method to produce these desired compounds where the association with lipase as a catalyst is a good alternative. However, the use of separate racemization catalyst and enzymes in the reaction medium still limits recovery, recycling and can occasionally be responsible for decreasing in selectivity for the desired product. In this work we proposed the synthesis and characterization of a hybrid magnetic catalyst composed containing lipase CaL B and Pd immobilized on the same recovered nanometric magnetic support for the application on Dynamic Kinetic Resolution of (rac)-1-phenylethylamine both in batch and continuous flow conditions. As results it was possible to achieve 99 % of conversion, with 95 % of selectivity and 93 % of enantiomeric excess after 12 h in batch. For a continuous flow system, it was possible to achieve 95 % of conversion with 71 % of selectivity and ee > 99 % after 60 min of reaction. The hybrid catalyst had around 50−100 nm with nanoparticulated Pd (5−10 nm) on its surface, presented a superparamagnetic behavior without remaining magnetization and 22 emu/g of saturation magnetization.

Combining Pd nanoparticles on MOFs with cross-linked enzyme aggregates of lipase as powerful chemoenzymatic platform for one-pot dynamic kinetic resolution of amines

Acquisition of chiral amines is a very important item in scientific research. Chemoenzymatic catalyst combination of Pd nanoparticles supported on the external surface of the ethylenediamine-functionalized MIL-101 (Pd@ED-MIL-101) with layered cross-linked enzyme aggregates of Candida antarctica lipase B (CALB-CLEAs) was established for the first time. This combination served as an ultra-efficient chemoenzymatic catalyst system for one-pot dynamic kinetic resolution (DKR) of rac-1-phenylethylamine leading to optically pure product (>99% ee value) with almost full conversion and excellent selectivity (>99%) without the aid of any additive. Significantly, aliphatic amines can be also efficiently converted to enantiomerically pure products, making this robust and heterogeneous combination one of the most powerful chemoenzymatic platforms for microwave-assisted one-pot DKR of amines available up to now.

Continuous-Flow Chemoenzymatic Dynamic Kinetic Resolution of Amines

Key words dynamic kinetic resolution - continuous flow - heterogenous catalysis - palladium catalysis

Chemoenzymatic Dynamic Kinetic Resolution of Amines in Fully Continuous-Flow Mode.

In this study, lipase-mediated dynamic kinetic resolution (DKR) of various benzylic amines (1a-g) is presented which is realized in a so far unprecedented fully continuous-flow system. The DKR process applying sol-gel immobilized lipase B from Candida antarctica as biocatalyst, palladium on 3-aminopropyl-functionalized silica as racemization catalyst, isopropyl 2-ethoxyacetate as acylating agent, ammonium formate as hydrogen and nitrogen sources, and 2-methyl-2-butanol as solvent under regulated pressure provided the desired products in moderate to good yields with excellent enantiomeric excesses.

Dynamic kinetic resolution of amines by using palladium nanoparticles confined inside the cages of amine-modified MIL-101 and lipase

Dynamic kinetic resolution (DKR) of amines is an important strategy for the synthesis of chiral drugs and their building blocks; however, improving the matchability of metal-catalyzed racemization and enzymatic resolution is still a task. In this paper, Pd nanoparticles (NPs) were encapsulated inside the cages of ethylenediamine-grafted MIL-101 (ED-MIL-101), giving highly efficient catalysts (Pd/ED-MIL-101) for the racemization of primary amines. The racemization can be combined with lipase-catalyzed resolution in a one-pot DKR of rac-1-phenylethylamine leading to optically pure product (>99% ee value) with an excellent conversion and selectivity up to 99% and 93%, respectively, superior to other catalysts, such as Pd/MIL-101, Pd/MCM-41 and commercially available Pd/C. Furthermore, the heterogeneous chemoenzymatic catalyst combination can be recovered and recycled 8 times without significant loss of efficiency. The enhance catalytic performances were found to depend on the amine modification of MIL-101 that not only endows the surface of its cages with basic property, but also enables efficiently confining Pd NPs in the cages. In addition, the matchability of such chemoenzymatic catalyst combination can be further enhanced by conducting the DKR process under microwave irradiation.

Preparation, Characterization and Catalytic Activity of Palladium Catalyst Supported on MgCO3 for Dynamic Kinetic Resolution of Amines

Pd nanoparticle catalyst loading 4.7 wt.% was prepared by the deposition-precipitation method and characterized by X-ray diffraction and transmission electron microscopy (TEM). The crystallite size estimated from the integral width of the highest intensity line using the Scherrer equation was 2.3 nm. Images obtained from TEM showed an equal distribution of the particles size between 0-2 and 2-4 nm, and also a good dispersion of the nanoparticles on the catalyst support. The catalytic activity of this nanocatalyst was studied for racemization reactions of (S)-(-)-1-phenylethylamine. After that, the catalyst was used in the chemoenzymatic dynamic kinetic resolution (DKR) of some primary amines. Expressive yields and optical purities were obtained.

Mild dynamic kinetic resolution of amines by coupled visible-light photoredox and enzyme catalysis.

Herein, we described photoenzymatic dynamic kinetic resolution (DKR) of amines under mild conditions. The racemization of amines via a photoredox-mediated hydrogen atom transfer (HAT) protocol in conjunction with an enzyme catalyst to achieve the DKR of amines allows a variety of primary amines to be converted into a single enantiomer in high yield and with excellent enantioselectivity. Notably, this protocol can also be extended to 1,4-diamine derivatives with high levels of diastereo- and enantioselectivity.

Highly efficient dynamic kinetic resolution of benzylic amines with palladium catalysts on oxidized multiwalled carbon nanotubes for racemization

A new and efficient dynamic kinetic resolution (DKR) process of benzylic amines was developed using palladium supported on surface-oxidized multiwalled carbon nanotubes (Pd/oxidized MWCNTs) as racemization catalyst. The catalyst Pd/oxidized MWCNTs was first used in the DKR of amines. Enantiomerically pure benzylic amide was obtained with high conversion and enantiomeric excess (ee) at 55°C. Possible side reactions were strongly suppressed and the catalyst system was used in ten successive reactions without loss of conversion or ee. The likely utility of the method was also reflected by the broad range of possible reaction substrates.

Chemoenzymatic dynamic kinetic resolution of primary amines using a recyclable palladium nanoparticle catalyst together with lipases.

A catalyst consisting of palladium nanoparticles supported on amino-functionalized siliceous mesocellular foam (Pd-AmP-MCF) was used in chemoenzymatic dynamic kinetic resolution (DKR) to convert primary amines to amides in high yields and excellent ee's. The efficiency of the nanocatalyst at temperatures below 70 °C enables reaction conditions that are more suitable for enzymes. In the present study, this is exemplified by subjecting 1-phenylethylamine (1a) and analogous benzylic amines to DKR reactions using two commercially available lipases, Novozyme-435 (Candida antartica Lipase B) and Amano Lipase PS-C1 (lipase from Burkholderia cepacia) as biocatalysts. The latter enzyme has not previously been used in the DKR of amines because of its low stability at temperatures over 60 °C. The viability of the heterogeneous Pd-AmP-MCF was further demonstrated in a recycling study, which shows that the catalyst can be reused up to five times.

Shvo's catalyst in chemoenzymatic dynamic kinetic resolution of amines – inner or outer sphere mechanism?

Evidence is provided for the inner-sphere mechanism with actual metal coordination of the racemic amine in the crucial hydrogen transfer step promoted by Shvo's catalyst of the chemoenzymatic dynamic kinetic resolution (DKR) of amines. Key intermediates involved in this H-transfer step were intercepted and continuously monitored by electrospray ionization mass spectrometry (ESI-MS) and characterized by their dissociation chemistries via ESI-MS/MS.

ChemInform Abstract: Dynamic Kinetic Resolution of Amines and Amino Acids by Enzyme—Metal Cocatalysis

AbstractReview: ca. 50 refs.

Dynamic Kinetic Resolution of Amines and Amino Acids by Enzyme–Metal Cocatalysis

AbstractMethods for the conversion of racemates to single enantiomers are of great importance in organic and pharmaceutical chemistry. Enzymatic kinetic resolution has been most frequently applied for such a conversion. It is particularly useful in preparing both R and S enantiomers at the same time. However, if one enantiomer is needed, the other should be recycled via racemization to enable high yields. Over the last two decades, in situ racemization of the unwanted enantiomers has been intensively studied with the development of metal‐based catalysts. Metal‐catalyzed racemization can be coupled with enzymatic kinetic resolution for the dynamic kinetic resolution of racemic amines and amino acids, which provides single enantiomeric products with yields approaching 100 %. Recent developments in this field are summarized with focus on metal catalysts for racemization.

Heterogeneous Catalysts for Racemization and Dynamic Kinetic Resolution of Amines and Secondary Alcohols

This paper gives an overview of the available heterogeneous catalysts for racemization of chirally stable secondary alcohols and amines, and of the combination of these catalysts with immobilized enzymes in dynamic kinetic resolution (DKR) for production of enantiopure esters or amides. For the one-pot DKR process, compatibility of enzyme and heterogeneous catalyst is a major issue, and in some cases the combination fails because of (mutual) deactivation. Heterogeneous catalysts of various types, such as zeolites or oxides effect alcohol racemization; they function either via acid catalysis and carbenium chemistry, or via a redox pathway via the ketone. Dynamic kinetic resolution of aliphatic alcohols using a heterogeneous catalyst in mild conditions is however an open challenge. Heterogeneous amine racemization catalysts invariably operate using a redox mechanism via the imine. In this case, the scope encompasses benzylic and aliphatic amines. The practicality of the approach is illustrated with the production of enantiopure N-acylated homoserine lactones, which are signalling compounds in microbial communities.

Heterogeneous Raney Nickel and Cobalt Catalysts for Racemization and Dynamic Kinetic Resolution of Amines

AbstractRaney metals were studied as heterogeneous catalysts for racemization and dynamic kinetic resolution (DKR) of chiral amines, as an alternative to metals like palladium or ruthenium. Both Raney nickel and cobalt were able to selectively racemize various chiral amines with high selectivity. In the racemization of benzylic primary amines, the minor formation of side products, e.g., secondary amines, can be suppressed by varying the hydrogen pressure. In the racemization of aliphatic amines over Raney catalysts, the selectivity is very high, with the enantiomeric amine as the sole product. DKR of racemic aliphatic amines can be performed with immobilized Candida antarctica lipase B and Raney nickel in one pot; for 2‐hexylamine, a yield of 95 % of the acetylated amide was achieved, with 97 % ee. Attention is devoted to the compatibility of the enzyme and the metal catalyst during the DKR. For benzylic primary amines, a two‐pot process is proposed in which the liquid is alternatingly shuttled between two vessels containing the solid racemization catalyst and the biocatalyst. After 4 such cycles, the amide of (R)‐1‐phenylethylamine was obtained with 94 % yield and more than 90 % ee.

Dynamic Kinetic Resolution of Amines Involving Biocatalysis and in Situ Free Radical Mediated Racemization

[reaction: see text] The association of lipase-catalyzed enzymatic resolution with in situ racemization mediated with the thiyl radical enables the dynamic kinetic resolution of non-benzylic amines. It leads to (R)-amides with high enantioselectivities. It can be applied either to the conversion of racemic mixtures or to the inversion of (S)-enantiomers.

Chemoenzymatic Dynamic Kinetic Resolution of Primary Amines

An efficient process for dynamic kinetic resolution of amines was developed by combining a ruthenium-catalyzed racemization with a lipase-catalyzed resolution. A variety of unfunctionalized primary amines were transformed into one enantiomer of the amide in high yield and high enantioselectivity.