Reduction Of Ketones Research Articles

Redox Biocatalysis in Lidocaine-based Hydrophobic Deep Eutectic Solvents: Non-conventional Media Outperform Aqueous Conditions.

Redox biocatalysis is an important pillar of the chemical industry. Yet, the enzymes' nature restricts most reactions to aqueous conditions, where the limited substrate solubility leads to unsustainable diluted biotranformations. Non-aqueous media represent a strategic solution to conduct intensified biocatalytic routes. Deep eutectic solvents (DESs) are designable solvents that can be customized to meet specific application needs. Within the large design space of combining DES components (and ratios), hydrophobic DESs hold the potential to be both enzyme-compatible - keeping the enzymes' hydration -, and solubilizers for hydrophobic reactants. We explored two hydrophobic DESs, lidocaine/oleic acid, and lidocaine/decanoic acid, as reaction media for carbonyl reduction catalyzed by horse liver alcohol dehydrogenase, focusing on the effect of water contents and on maximizing substrate loadings. Enzymes remained highly active and stable in the DESs with 20 wt.% buffer, whereas the reaction performance in DESs outperformed the pure buffer system with hydrophobic substrates (e.g., cinnamaldehyde to form the industrially relevant cinnamyl alcohol), with a 2-fold higher specific activity. Notably, the cinnamaldehyde reduction was for the first time performed at 800 mM (~100 g[[EQUATION]]L-1) with full conversion, which opens up new avenues to industrial applications of hydrophobic DESs for enzyme catalysis.

Enantiomerically Pure Indazole Bioisosteres of Ifenprodil and Ro 25-6981 as Negative Allosteric Modulators of NMDA Receptors with the GluN2B Subunit.

Administration of negative allosteric modulators of GluN2B subunit-containing NMDA receptors such as Ro 25-6981 (1) and ifenprodil (2) results in neuroprotective effects. In this study, the phenol of 1 and 2 was replaced bioisosterically by an indazole to inhibit glucuronidation. The γ- and β-aminoalcohols 10 and 11 were prepared without installing a protective group at the indazole ring using the ketone 6 as a common intermediate. All four stereoisomeric γ- and β-aminoalcohols 10 and 11 were obtained by diastereoselective reduction of ketones 7 and 9 followed by separation of enantiomers. The analogously structured γ-aminoalcohol (1S,2S)-10c (Ro 25-6981 bioisostere) and β-aminoalcohol (1R,2R)-11c (ifenprodil bioisostere) exhibited high GluN2B affinity (Ki = 50 and 66 nM, respectively) and high to moderate inhibitory activity in two-electrode voltage clamp experiments. The indazole bioisosteres 10 and 11 showed higher metabolic stability than 1. In the presence of uridinyldiphosphate activated glucuronic acid, glucuronidation of 10 and 11 was not observed.

Bioreduction of aromatic ketones catalyzed by oak fruits (Quercus Ilex L ) fruit grown in north Algeria

The present work primarily aims to investigate and establish a method for the bioreduction of aromatic ketones to produce corresponding alcohols. This process is crucial for the production of various industrially important chemicals, including pharmaceuticals, agrochemicals, and natural products, and supports the principles of green chemistry. Additionally, this study seeks to valorize the vegetation cover in southern Algeria as a source of biochemical catalysts. Our research focused on the bioreduction of several acetophenone derivatives using the fruits of Oak (Quercus ilex L.) which is cultivated in northern Algeria. The findings indicate that these plant tissues can effectively reduce acetophenone derivatives. Specifically, a chemical yield of approximately 90% was achieved for acetophenone, while yields ranged from 60% to 75% for 4'-haloacetophenones (where X = F, Cl, and Br) and 4'-nitroacetophenone. These results demonstrate that (Quercus ilex L).fruits from northern Algeria can serve as effective biocatalysts in the reduction of aromatic ketones to their corresponding alcohols. This approach not only supports the sustainable production of pharmaceuticals but also provides significant health, environmental, economic, and medical benefits.

Shining light on green chemistry: BODIPY-infused porphyrin nanocomposite-enzymatic photocatalyst boosts selective aldehydes hydrogenation and organic transformation under solar spectrum

Photo-bio enzyme coupled biotransformation solar radiation driven processes grasp promising in the production of solar driven organic chemicals. Here we reported the synthesis and development of (NH2)4TPP@BODIPY photocatalyst, which was constructed from 5,10,15,20 tetrakis (4 amino phenyl) porphyrin and BODIPY {5,5-difluoro-3,7-bis((E)-4-nitrobenzylidene)-10-(4-nitrophenyl)-5,7-dihydro-3H-4l4,5l4-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinine} molecule through poly-condensation mechanism resulting in the composite formation which manifest excellent light harvesting properties and photocatalytic reactions with suitable satisfactory band gap and formation of huge electrons channels which bears the organic transformation (98 %) and photo-regeneration of NADH (66.92 %) in 60 min which further enhances reduction of aldehyde resulting alcohol production. The highly selective aldehyde hydrogenation process is proposed via coordination of alcohol dehydrogenase with (NH2)4TPP@BODIPY assistant reduces from the coupling process; regeneration of nicotinamide adenine dinucleotide (NADH). Our results show an excellent benchmark for the NAD+ co-factor coupled solar-driven alcohol production via (NH2)4TPP@BODIPY photocatalyst.

A mild and chemoselective photoredox-catalyzed reduction of aromatic ketones

A mild, chemoselective reduction of aromatic ketones was discovered and investigated. The combination of photoredox and Lewis acid catalysis with an organic hydrogen source reduced aromatic ketones in good to high yield. Optimization found 2-phenylbenzothiazoline to be a sufficiently strong source of hydrogen in combination with an iridium photosensitizer and lanthanum triflate. Effective photomediated reduction of some substrates was also observed in the absence of photocatalyst and Lewis acid or with photocatalyst only. While yields were typically higher under catalytic conditions, some acid-sensitive substrates were more effectively reduced in the absence of Lewis acid. The reaction was generally high yielding, and chemoselecte, while tolerant of complex and functionally rich molecules.

Nickel Boride as Hydride Source in Nickel Catalyzed Chemoselective Reduction of α,β‐Unsaturated Amides

AbstractA facile and highly efficient chemoselective reduction of α,β‐unsaturated amides leading to saturated amide has been described. In situ generated nickel boride was found to act as an efficient reagent for the conjugate reduction. The reaction proceeds smoothly under an inert atmosphere at ambient temperature with a moderate to good yield. Both aliphatic and aromatic α,β‐unsaturated amides were found to be compatible with the reaction protocol.

PPh3-catalyzed chemoselective reduction of aldehydes to alcohols

Reduction of aldehydes to alcohols is a fundamental organic transformation, typically achieved through metal-catalyzed reductions or by the use of hydride-based reagents. However, these conventional methods often go through harsh conditions with expensive catalysts and additional reductants, limiting their broader applications. In this study, for the first time we introduce an efficient, metal-free reduction strategy using triphenylphosphine (PPh3) and KOtBu in MeOH. This method exhibits broad functional group tolerance, mild environment and selectivity in reducing aldehydes even in the presence of other reactive functionalities (NO2, CN, ketone, etc.). Key features highlight this novel approach with practicality, scalability to gram scales and excellent yields for the reduction of varied aldehydes to alcohols (30 examples; 65–95 % Yields).

Cooperative chemoenzymatic and biocatalytic cascades to access chiral sulfur compounds bearing C(sp3)–S stereocentres

Biocatalysis has been widely employed for the generation of carbon-carbon/heteroatom stereocentres, yet its application in chiral C(sp3)–S bond construction is rare and limited to enzymatic kinetic resolutions. Herein, we describe the enantioselective construction of chiral C(sp3)–S bonds through ene-reductase biocatalyzed conjugate reduction of prochiral vinyl sulfides. A series of cooperative sequential/concurrent chemoenzymatic and biocatalytic cascades have been developed to access a broad range of chiral sulfides, including valuable β-hydroxysulfides bearing two adjacent C(sp3)–S and C(sp3)–O stereocentres, in a stereoconvergent manner with good to excellent yields (up to 96%) and enantioselectivities (up to >99% ee). Notably, this biocatalytic strategy allows to overcome the long-standing shortcomings of catalyst poisoning and C(sp2)/C(sp3)–S bond cleavage faced in transition-metal-catalyzed hydrogenation of vinyl sulfides. Finally, the potential of this methodology is also exemplified by its broader application in the stereoconvergent assembly of chiral C(sp3)–N/O/Se bonds with good to excellent enantioselctivities.

Optimizing the fermentation parameters in the Lactic Acid Fermentation of Legume-based Beverages– a statistically based fermentation

BackgroundThe market for beverages is highly changing within the last years. Increasing consumer awareness towards healthier drinks led to the revival of traditional and the creation of innovative beverages. Various protein-rich legumes were used for milk analogues, which might be also valuable raw materials for refreshing, protein-rich beverages. However, no such applications have been marketed so far, which might be due to unpleasant organoleptic impressions like the legume-typical “beany” aroma. Lactic acid fermentation has already been proven to be a remedy to overcome this hindrance in consumer acceptance.ResultsIn this study, a statistically based approach was used to elucidate the impact of the fermentation parameters temperature, inoculum cell concentration, and methionine addition on the fermentation of lupine- and faba bean-based substrates. A total of 39 models were found and verified. The majority of these models indicate a strong impact of the temperature on the reduction of aldehydes connected to the “beany” impression (e.g., hexanal) and on the production of pleasantly perceived aroma compounds (e.g., β-damascenone). Positively, the addition of methionine had only minor impacts on the negatively associated sulfuric compounds methional, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide. Moreover, in further fermentations, the time was added as an additional parameter. It was shown that the strains grew well, strongly acidified the both substrates (pH ≤ 4.0) within 6.5 h, and reached cell counts of > 9 log10 CFU/mL after 24 h. Notably, most of the aldehydes (like hexanal) were reduced within the first 6–7 h, whereas pleasant compounds like β-damascenone reached high concentrations especially in the later fermentation (approx. 24–48 h).ConclusionsOut of the fermentation parameters temperature, inoculum cell concentration, and methionine addition, the temperature had the highest influence on the observed aroma and taste active compounds. As the addition of methionine to compensate for the legume-typical deficit did not lead to an adverse effect, fortifying legume-based substrates with methionine should be considered to improve the bioavailability of the legume protein. Aldehydes, which are associated with the “beany” aroma impression, can be removed efficiently in fermentation. However, terminating the process prematurely would lead to an incomplete production of pleasant aroma compounds.

Stereoselective Approach to the Core Structure of (+)-Phainanoid A via Strategically Engineered Cascade Polyene Cyclization.

Stereoselective synthesis of 3b and its cascade polyene cyclization to 18b have been described. Acyclic polyene 3b was prepared from allyl bromide 4 and 1,3-dithiane 5, and intermediates 4 and 5 were synthesized from the commercially available geraniol (6) and cyclopenten-2-one (8), respectively, using enantioselective reduction of ketone, Johnson-Claisen rearrangement, and the Suzuki reaction as key steps. Au(I)-mediated diastereoselective polyene cyclization of 3b efficiently afforded tetracyclic compound 18b.

Rational design of short-chain dehydrogenase/reductase for enantio-complementary synthesis of chiral 1,2-diols by successive hydroxymethylation and reduction of aldehydes.

Enantiopure 1,2-diols are widely used in the production of pharmaceuticals, cosmetics, and functional materials as essential building blocks or bioactive compounds. Nevertheless, developing a mild, efficient and environmentally friendly biocatalytic route for manufacturing enantiopure 1,2-diols from simple substrate remains a challenge. Here, we designed and realized a step-wise biocatalytic cascade to access chiral 1,2-diols starting from aromatic aldehyde and formaldehyde enabled by a newly mined benzaldehyde lyase from Sphingobium sp. combined with a pair of tailored-made short-chain dehydrogenase/reductase from Pseudomonas monteilii (PmSDR-MuR and PmSDR-MuS) capable of producing (R)- and (S)-1-phenylethane-1,2-diol with 99% ee. The planned biocatalytic cascade could synthesize a series of enantiopure 1,2-diols with a broad scope (16 samples), excellent conversions (94%-99%), and outstanding enantioselectivity (up to 99% ee), making it an effective technique for producing chiral 1,2-diols in a more environmentally friendly and sustainable manner.

Electrochemical Hydrodimerization of Lignocellulose-derived Carbonyls in Aqueous Electrolytes for Biobased Polymer and Long-chained Synfuel Production: A Review.

The transformation from fossil resources, crude oil and natural gas to biomass-derived feedstocks is an urgent and major challenge for the chemical industry. The valorization of lignocellulose as renewable resource is a promising pathway offering access to a wide range of platform chemicals, such as vanillin, furfural and 5-HMF. The subsequent conversion of such platform chemicals is one crucial step in the value-added chain. The electrochemical hydrodimerization (EHD) is a sustainable tool for C-C coupling of these chemicals to their corresponding hydrodimers hydrovanilloin, hydrofuroin and 5,5´-bis(hydroxymethyl)hydrofuroin (BHH). This review covers the current state of art concerning the mechanism of the electrochemical reduction of biobased aldehydes and studies targeting the electrochemical production of these hydrodimers in aqueous media. Moreover, the subsequent conversion of these hydrodimers to valuable additives, polymers and long carbon chain synfuels will be summarized offering a broad scope for their application in the chemical industry.

Elevated blood-ethanol concentration promotes reduction of aliphatic ketones (acetone and ethyl methyl ketone) to secondary alcohols along with slower oxidation to aliphatic diols.

Many people convicted for drunken driving suffer from an alcohol use disorder and some traffic offenders consume denatured alcohol for intoxication purposes. Venous blood samples from people arrested for driving under the influence of alcohol were analyzed in triplicate by headspace gas chromatography (HS-GC) using three different stationary phases. The gas chromatograms from this analysis sometimes showed peaks with retention times corresponding to acetone, ethyl methylketone (2-butanone), 2-propanol, and 2-butanol in addition to ethanol and the internal standard (1-propanol). Further investigations showed that these drink-driving suspects had consumed an industrial alcohol (T-Red) for intoxication purposes, which contained > 90% w/v ethanol, acetone (~ 2% w/v), 2-butanone (~ 5% w/v) as well as Bitrex to impart a bitter taste. In n = 75 blood samples from drinkers of T-Red, median concentrations of ethanol, acetone, 2-butanone, 2-propanol and 2-butanol were 2050mg/L (2.05g/L), 97mg/L, 48mg/L, 26mg/L and 20mg/L, respectively. In a separate GC analysis, 2,3-butanediol (median concentration 87mg/L) was identified in blood samples containing 2-butanone. When the redox state of the liver is shifted to a more reduced potential (excess NADH), which occurs during metabolism of ethanol, this favors the reduction of low molecular ketones into secondary alcohols via the alcohol dehydrogenase (ADH) pathway. Routine toxicological analysis of blood samples from apprehended drivers gave the opportunity to study metabolism of acetone and 2-butanone without having to administer these substances to human volunteers.

Coupling photocatalytic trifluoromethylation with biocatalytic stereoselective ketone reduction in continuous flow

Photocatalysis and biocatalysis represent powerful efficient tools in synthetic chemistry. While, both have individually shown promising results, their integration remains challenging, particularly in continuous flow processes. This work presents a semicontinuous setup, combining photo- and biocatalysis in a multistep synthesis for the production of optically pure (S)-3,3,3-trifluoro-1-phenylpropan-1-ol. Initially, a photocatalytic trifluoromethylation of a methyl ketone in α-position in a self-made photoreactor was tested in flow, followed by enzymatic ketone reduction catalyzed by an alcohol dehydrogenase (variant of an ADH from Lactobacillus kefir). The study addresses the challenge of enzyme stability in aggressive solvents, developing a robust immobilization approach for the selected ADH with a PVA/PEG cryogel matrix. This strategy has been investigated in this work to ensure enzyme stability in THF, marking a notable advance in compatibility for continuous cascades. The separate process steps were finally combined in a semicontinuous flow system, achieving a space–time yield for the photocatalytic step of 39.8 g L−1 h−1 and of 1.12 g L−1 h−1 for the enzymatic step. The study signifies one of the first instances of combining photo- and biocatalysis in continuous cascades, offering an innovative approach to synthesizing chiral 3,3,3-trifluoro-1-phenylpropan-1-ol.Graphical abstract

An efficient route for synthesis of spirocyclic cyclopentapyridines

Pyridine spirocycles play an important role in drug design and development. In this paper, a novel spirocyclic cyclopentapyridine compound was synthesized. Based on retrosynthesis analysis, commercially available 2-chloro-6-methoxypyridine was used as the starting material for the synthesis of the target molecule, accomplished through an eight-step reaction process. Particular emphasis was placed on the two most challenging steps: selective Negishi coupling and carbonyl reduction.

(Invited) Introducing Selectivity into Electrochemical Reactions: From Solution to Surfaces

Induction of asymmetry into electrosynthetic reactions has taken off in recent years for the electrochemical community. As of late most transformations have focused on either simple electrochemical oxidations or reductions, such as the reduction of various ketones to chiral alcohol feedstock molecules, or transition metal cross coupling reactions. At the same time, there has been little effort to introduce asymmetry into cyclization reactions that capitalize on highly reactive radical ion intermediates to accomplish umpolung-type transformations or to fully take advantage of electrode surfaces for manipulating the selectivity of synthetically more complex transformations like transition metal cross coupling reactions. In the case more complex electrochemical transformations, many of the reactions studied have led to either high ee and low yield or low ee and high yield. With this in mind, we are looking new approaches for introducing selectivity into electrochemical transformations by taking advantage of high yielding cathodic cyclization reactions and the Heck reaction. The influence of chiral electrolytes, chiral catalysts and mediators, and modified electrode surfaces on these transformations is being explored with a particular emphasis on both the induction of asymmetry into the reactions and the use of remote functionality in the molecules as a control element. This presentation to be given will detail our progress in these areas.

Novel Electrocatalytic Hydrogenation Using a Solid Polymer Electrolyte (SPE) Reactor

Organic electrosynthetic reactions, which are driven by electricity, can generally be carried out under mild conditions (room temperature and ambient pressure). In addition, they do not require any hazardous reagents and produce less waste than other conventional chemical syntheses. Therefore, electrosynthesis is known to be a mild and clean method for organic synthesis and there has recently been renewed interest in its development. However, electrosynthesis also has some disadvantages. Ordinary chemical reactions are homogeneous, while the reaction field of electrolysis is a heterogeneous interface, therefore electrosynthesis has a productive drawback. In addition, a large amount of supporting electrolyte is usually required. Therefore, the availability of solvents is limited by the necessity for dissolution of a supporting electrolyte. The presence of the supporting electrolyte might also cause separation problems in the reaction workup. Moreover, in an ordinary electrolysis system, solution resistance is generated between the working and counter electrodes, resulting in a decrease in energy efficiency. To overcome these problems, we focused on a solid polymer electrolyte (SPE) reactor which was originally developed for fuel cell technologies and demonstrated various electrocatalytic hydrogenations in a SPE reactor (Figure 1) [1-5].As shown in Figure 1, a SPE membrane such as a proton exchange membrane (PEM) is integrated into the central part of the reactor, and is sandwiched between a pair of catalyst layers on the anode and cathode sides. For this reason, the substrate solution does not require a supporting electrolyte and the cell resistance can be minimized. The anode and cathode have highly porous 3D structures in order to conduct an efficient electrochemical reaction. Moreover, the reaction can be carried out in a flow operation. Thus, the SPE reactor system possesses many characteristics designed to overcome the disadvantages of conventional electrosynthetic processes.In a series of studies we have conducted, in this presentation, we will discuss two topics such as diastereoselective reduction of cyclic ketones and electrocatalytic hydrogenation of pyridines.The authors gratefully acknowledged support by JST CREST Grant No. 18070940, Japan.[1] A. Fukazawa, M. Atobe, et al. ACS Susutain. Chem. Eng. 2019, 7, 11050.[2] S. Nogami, M. Atobe, et al. J. Electrochem. Soc. 2020, 167, 155506.[3] A. Fukazawa, M. Atobe, et al. Org. Biomol. Chem. 2021, 19,7363.[4] S. Nogami, M. Atobe, et al. ACS Catalysis, 2022, 12, 5430.[5] Y. Shimizu, M. Atobe, et al. ACS Energy Lett., 2023, 8, 1010. Figure 1

Direct Hydrogenation of Sterically Hindered, Unactivated Alkenes Catalyzed by Phosphino(silyl)‐Nickel Complexes

AbstractReadily accessible (PSi)Ni(II)‐benzyl complexes supported by bidentate phosphino(silyl) ligation were found to be effective pre‐catalysts for the direct hydrogenation of a variety of highly sterically hindered, unfunctionalized alkenes under relatively mild conditions (2.5‐5 mol% Ni, 10 atm H2, 50 °C) and without the need for additional additives or activator species. A range of substrates, including di‐, tri‐, and tetra‐substituted alkenes were evaluated in this regard and afforded good to moderate yields. Substrates featuring α,β‐unsaturated carbonyl functionality were also readily hydrogenated with no evidence for reduction of carbonyl or ester C−O functionalities. Deuteration experiments highlight the occurrence of chain walking which occurs in the background of the reported catalytic chemistry.

Polyoxometalates Based Catalysts for Carbonylation Reactions: A Review.

As a type of diverse and structurally adjustable metal-oxo clusters, polyoxometalates (POMs) based materials have been extensively applied as a catalysis in various valuable reactions. This review summarized recent progress in the application of POMs-based catalysts for various carbonylation reactions including (1). Carbonylation of olefins, (2). Carbonylation of formaldehyde, (3). Carbonylation of methanol or dimethyl ether, (4). Oxidative carbonylation of methane, (5). Oxidative carbonylation of phenol and (6). Reductive carbonylation of nitrobenzene. A brief perspective on POMs-based catalysts for the carbonylation reactions is proposed.

Mononuclear Aluminum Complexes as Precursors for Cyanosilylation of Carbonyl Compounds

AbstractThe synthesis, structural characterization, and catalytic application of two novel aluminum complexes, [κ3ENSe−{Ph2P(E)N−C6H4−SePh}AlMe2] [E=S (1) and Se (2)] supported by new pincer‐type phenylselenium‐phosphanamidinate chalcogenide ligands are described. The molecular structures of both complexes in their solid states reveal a distorted trigonal bipyramidal geometry around the Al(III) ion, involving monoanionic ligand {Ph2P(E)N−C6H4−SePh}− bonded to the AlMe2‐motif in a tridentate manner. Complex 1 was found to be an effective pre‐catalyst for the cyanosilyation of aldehydes and ketones with TMSCN under solvent‐free conditions. The reaction protocol is simple, efficient, and has a diverse substrate scope of aldehydes and ketones, showing superior functional group tolerance. The kinetic study revealed that ketone reduction proceeded with first‐order dependence on ketone concentrations, TMSCN, and catalyst 1.