Synthesis Of Fine Chemicals Research Articles

Palladium and Copper: Advantageous Nanocatalysts for Multi-Step Transformations.

Metal nanoparticles have been deeply studied in the last few decades due to their attractive physical and chemical properties, finding a wide range of applications in several fields. Among them, well-defined nano-structures can combine the main advantages of heterogeneous and homogeneous catalysts. Especially, catalyzed multi-step processes for the production of added-value chemicals represent straightforward synthetic methodologies, including tandem and sequential reactions that avoid the purification of intermediate compounds. In particular, palladium- and copper-based nanocatalysts are often applied, becoming a current strategy in the sustainable synthesis of fine chemicals. The rational tailoring of nanosized materials involving both those immobilized on solid supports and liquid phases and their applications in organic synthesis are herein reviewed.

Highly Selective Indole Oxidation Catalyzed by a Mn-Containing Artificial Mini-Enzyme

Indole oxidation represents a real challenge for selectivity because it typically leads to complex mixtures of products even when highly selective enzymes are used. Here, we describe the catalytic potential of an artificial enzyme, Mn-Mimochrome VI*a (Mn-MC6*a), in promoting indole oxidation. This mini-enzyme contains a manganese–deuteroporphyrin active site within a scaffold of two synthetic small peptides covalently linked to porphyrin. Mn-MC6*a promotes the selective oxidation of indole at its C3 position, leading to a 3-oxindole derivative (2-TFE-3-oxindole) with unprecedented product selectivity (86% at pH 8.5) compared to native or artificial heme-enzymes. We also suggest a possible reaction mechanism based on the effect of pH, cosolvent, and indole substitution on the reaction outcome. These studies demonstrate that Mn-MC6*a is an excellent artificial peroxygenase for the production of 3-oxindole-containing compounds as key building blocks for the synthesis of fine chemicals.

Recent reports on Pyridoxal derived Schiff base complexes

Abstract Pyridoxal and Pyridoxal 5-phosphate are two among the six aqua soluble vitamers of vitamin B6. They can form Schiff bases readily due to the presence of aldehyde group. Schiff bases can offer diverse coordination possibilities for many transition metals as has been found in a large volume of research till now. The coordination complexes thus formed gives insight into the active core structure and enzymatic activities of vit B6 containing enzymes. Apart from that, these complexes have been found useful as catalysts for synthesis of fine chemicals, as sensors and for their diverse biological activities.

Homogeneously catalyzed acceptorless dehydrogenation of alcohols: A progress report

• Acceptorless dehydrogenation of alcohols to high value chemicals by homogeneous catalysts. • Acceptorless dehydrogenation of alcohols for future applications as hydrogen storage systems. • Multifunctional ligands in the coordination sphere of a metal center to improve catalytic activity. • Novel metal–ligand cooperativity to enable non-precious metal catalysis. Catalytic dehydrogenation of alcohols represents an attractive approach for future applications as hydrogen storage systems and clean synthesis of fine chemicals. Herein, an overview of recent progress in homogeneously catalyzed acceptorless alcohol dehydrogenation is presented. In Nature, dehydrogenation of alcohols is efficiently catalyzed by multiple metalloenzymes where a non-noble metal–ligand interplay is key to activate and transform a substrate. We highlight the introduction of multifunctional cooperative ligands in the coordination sphere of the metal center in order to improve catalytic activity under photochemical, electrochemical or thermal conditions. Moreover, metal–ligand cooperativity is crucial for an easy transition to first row metal based catalysis, as we have seen in the recent years.

A multi-enzyme cascade for efficient production of d-p-hydroxyphenylglycine from l-tyrosine

In this study, a four-enzyme cascade pathway was developed and reconstructed in vivo for the production of d-p-hydroxyphenylglycine (D-HPG), a valuable intermediate used to produce β-lactam antibiotics and in fine-chemical synthesis, from l-tyrosine. In this pathway, catalytic conversion of the intermediate 4-hydroxyphenylglyoxalate by meso-diaminopimelate dehydrogenase from Corynebacterium glutamicum (CgDAPDH) was identified as the rate-limiting step, followed by application of a mechanism-guided “conformation rotation” strategy to decrease the hydride-transfer distance d(C6HDAP−C4NNADP) and increase CgDAPDH activity. Introduction of the best variant generated by protein engineering (CgDAPDHBC621/D120S/W144S/I169P with 5.32 ± 0.85 U·mg−1 specific activity) into the designed pathway resulted in a D-HPG titer of 42.69 g/L from 50-g/L l-tyrosine in 24 h, with 92.5% conversion, 71.5% isolated yield, and > 99% enantiomeric excess in a 3-L fermenter. This four-enzyme cascade provides an efficient enzymatic approach for the industrial production of D-HPG from cheap amino acids.

Genetically Programmable Microbial Assembly.

Engineered microbial communities show promise in a wide range of applications, including environmental remediation, microbiome engineering, and synthesis of fine chemicals. Here we present methods by which bacterial aggregates can be directed into several distinct architectures by inducible surface expression of heteroassociative protein domains (SpyTag/SpyCatcher and SynZip17/18). Programmed aggregation can be used to activate a quorum-sensing circuit, and aggregate size can be tuned via control of the amount of the associative protein displayed on the cell surface. We further demonstrate reversibility of SynZip-mediated assembly by addition of soluble competitor peptide. Genetically programmable bacterial assembly provides a starting point for the development of new applications of engineered microbial communities in environmental technology, agriculture, human health, and bioreactor design.

Chemical Fixation of Carbon Dioxide by Heterogeneous Porous Catalysts

AbstractAs the ultimate carbon emission of the combustion process, carbon dioxide (CO2) is a serious environmental hazard in increasing the global climate temperature through the greenhouse effect. Porous heterogeneous catalysts have drawn huge interest for carbon capture and in the past decades; significant developments can be observed in their fabrication and implementation for CO2 capture and conversion. In this context, the emerging development in major porous heterogeneous catalysts such as MOFs, COFs, metal oxides etc. for CO2 capture and conversion are discussed. Their physiochemical properties and their influence on the efficiency for CO2 capture and conversion are enlightened. The review provides a concise report on various types of heterogeneous catalysts, current trends, their application in CO2 reduction and fixation for the synthesis of fuels and other important fine chemicals and future research directions for the deployment of porous heterogeneous catalysts in Carbon dioxide capture and conversion.

Towards Economic and Sustainable Amination with Green and Renewable Feedstocks

AbstractThe synthesis of N‐substituted amines is one of the key transformations in synthetic chemistry and chemical industry, because amines are ubiquitous in the syntheses of agrochemicals, pharmaceuticals, flavorings, fragrances, and advanced materials. In order to realize the clean and economic synthesis of N‐substituted amines, several aspects should be concerned. 1) The application of alkyl halides as alkylation reagents should be replaced by alcohol and alkane; 2) the employment of amines as nitrogen sources can be replaced by nitrobenzene, nitrile and ammonia; 3) the application of environmentally benign and low‐cost starting materials, such as CO2, HCHO, biomass resources, for the nitrogen‐containing chemicals synthesis should be established; and 4) economic, green and efficient catalyst should be developed for the above transformations. In this account, we describe our results in the clean and economic synthesis of N‐substituted amines with amine, ammonia, nitrobenzene or nitrile as nitrogen sources and alcohol, alkane or CO2, HCHO, CO, and biomass resources as alkylation or carbonylation reagents. What is the most favorite and original chemistry developed in your research group?Efficient and economic heterogeneous catalyst for catalytic amination.How do you get into this specific field? Could you please share some experiences with our readers?I got my introduction to fine chemical synthesis with heterogeneous catalyst during the post‐graduate and post‐doctor periods. Till now, the clean and economic synthesis of some fine chemicals still remains a big problem in China. Therefore, our group has been concentrating on catalyst design and preparation for amination since 11 years ago. Typically, we want to explore some novel catalyst systems to bridge the heterogeneous and homogeneous catalysis.What is the most important personality for scientific research?I think the originality and creativity are very important for the scientific research.What are your hobbies? What's your favorite book(s)?Reading and walking. I like to read history books.How do you keep balance between research and family?Although it is difficult, I try to keep a balance between research and family.Who influences you mostly in your life?My Ph.D. supervisor, Prof. Youquan Deng, and postdoctoral collaborating advisor, Prof. Matthias Beller.

A Hierarchical-Structured Impeller with Engineered Pd Nanoparticles Catalyzing Suzuki Coupling Reactions for High-Purity Biphenyl

Suzuki cross-coupling reactions catalyzed by palladium are authoritative protocols in fine-chemical synthesis. Mass transfer and catalyst activity are both significant factors affecting the reaction efficiency in heterogeneous reactions. Although the holistic catalysts hold great promise in heterogeneous reactions due to the enhanced mass transport and convenient recycling, the unsatisfied catalytic activity has impeded further large-scale applications. In addition, another pronounced barrier is the product separation in the intricate system. Here, the catalytic production and separation of biphenyl (purity of 99.7%) were achieved by integrating the Suzuki cross-coupling reactions and the crystallization separation for the first time. A hierarchical-structured impeller with Pd nanoparticles (NPs) loaded on the Ni(OH)2 nanosheets was prepared to catalyze the Suzuki reactions for bromobenzene, which exhibits a high turnover frequency (TOF) value of 25,976 h-1 and a yield of 99.5%. The X-ray absorption fine structure (XAFS) analysis has unveiled that the electron transfer between the Pd NPs and Ni(OH)2 accounts for the greatly enhanced catalytic activity. The findings inspire new insights toward rational engineering of highly efficient holistic catalysts for Suzuki reaction, and the innovative integrated technology offers an avenue for the separation and collection of products.

Less Unfavorable Salt Bridges on the Enzyme Surface Result in More Organic Cosolvent Resistance.

Biocatalysis for the synthesis of fine chemicals is highly attractive but usually requires organic (co‐)solvents (OSs). However, native enzymes often have low activity and resistance in OSs and at elevated temperatures. Herein, we report a smart salt bridge design strategy for simultaneously improving OS resistance and thermostability of the model enzyme, Bacillus subtilits Lipase A (BSLA). We combined comprehensive experimental studies of 3450 BSLA variants and molecular dynamics simulations of 36 systems. Iterative recombination of four beneficial substitutions yielded superior resistant variants with up to 7.6‐fold (D64K/D144K) improved resistance toward three OSs while exhibiting significant thermostability (thermal resistance up to 137‐fold, and half‐life up to 3.3‐fold). Molecular dynamics simulations revealed that locally refined flexibility and strengthened hydration jointly govern the highly increased resistance in OSs and at 50–100 °C. The salt bridge redesign provides protein engineers with a powerful and likely general approach to design OSs‐ and/or thermal‐resistant lipases and other α/β‐hydrolases.

Less Unfavorable Salt Bridges on the Enzyme Surface Result in More Organic Cosolvent Resistance

AbstractBiocatalysis for the synthesis of fine chemicals is highly attractive but usually requires organic (co‐)solvents (OSs). However, native enzymes often have low activity and resistance in OSs and at elevated temperatures. Herein, we report a smart salt bridge design strategy for simultaneously improving OS resistance and thermostability of the model enzyme, Bacillus subtilits Lipase A (BSLA). We combined comprehensive experimental studies of 3450 BSLA variants and molecular dynamics simulations of 36 systems. Iterative recombination of four beneficial substitutions yielded superior resistant variants with up to 7.6‐fold (D64K/D144K) improved resistance toward three OSs while exhibiting significant thermostability (thermal resistance up to 137‐fold, and half‐life up to 3.3‐fold). Molecular dynamics simulations revealed that locally refined flexibility and strengthened hydration jointly govern the highly increased resistance in OSs and at 50–100 °C. The salt bridge redesign provides protein engineers with a powerful and likely general approach to design OSs‐ and/or thermal‐resistant lipases and other α/β‐hydrolases.

Oxygen-vacancy-mediated energy transfer for singlet oxygen generation by diketone-anchored MIL-125

The importance of singlet oxygen (1O2) in synthesis of fine chemicals, inactivation of viruses and bacteria, degradation of pollutants, and photodynamic therapy has promoted the research on photocatalytic generation of 1O2. Metal-organic frameworks (MOFs), owing to the tunable structure, are good candidate photocatalysts for 1O2 generation. However, due to the poor visible-light absorption capacity and the invalid recombination of charge carriers, the 1O2 generation yields of most MOFs are still limited. Here, we demonstrate that β-diketone anchoring could improve the photocatalytic generation of 1O2 by MIL-125 through enhanced energy transfer. The enhanced energy transfer was attributed to both the narrowed bandgap and the diketone-derived oxygen vacancies, which function as the trapping sites for charge carriers. The results here shed light on the generation of 1O2 by visible-light-responsive MOFs and provide a new strategy for the design of MOFs-based photocatalysts.

Zirconium-based metal-organic framework as an efficiently heterogeneous photocatalyst for oxidation of benzyl halides to aldehydes

UiO-66-NH 2 is able to catalyze the oxidation of benzyl halides to aldehydes under mild and environment friendly conditions. • Metal organic frameworks was first used for the catalytic oxidation of benzyl bromide to benzaldehyde. • UiO-66-NH2 was applied as an reusable photocatalyst for conversion of benzyl halides to aldehydes with high selectivity and conversion. • This study provides general, environmental and high selective preparation of benzaldehydes. • This study broadens the application scope of UiO-66-NH 2 catalysts. The development of efficient heterogeneous catalysts for fine chemical synthesis is critical for practical applications. Herein, for the first time, the zirconium-based metal-organic framework (UiO-66-NH 2 ) is applied as an efficiently heterogeneous photocatalyst for conversion of benzyl halides to corresponding aldehydes with high selectivity (about 80 %) and conversion (up to 99 %) in the presence of oxygen and DMF as solvent. Through a series of experiments and analysis, the reaction mechanism is proposed to involve nucleophilic attack of the N -oxide. This study provides a general, environmental and high selective method to prepare benzaldehydes and broadens the application fields of UiO-66-NH 2 .

MgO nanoparticles: Synthesis, characterization, and applications as a catalyst for organic transformations

Currently, the size and shape selective synthesis of nanoparticles (NPs) and their varied catalytic applications are gaining significant enthusiasm in the field of nanochemistry. Homogeneous catalysis is crucial due to its inherent benefits like high selectivity and mild reaction conditions. Nevertheless, it endures with serious disadvantages of catalysts and/or product separation/recycles compared to their heterogeneous counterparts restricting their catalytic applications. The utilization of catalysts in the form of nano-size is an elective methodology for the combination of merits of homogeneous and heterogeneous catalysis. Magnesium oxide (MgO) NPs are important as they find applications for catalysis, organic transformation, and synthesis of fine chemicals and organic intermediates. The applications of MgO NPs in diverse organic transformations including oxidation, reduction, epoxidation, condensation, and C-C, C-N, C-O, C-S bond formation in a variety of notable heterocyclic reactions are also discussed. The use of MgO NPs in organic transformation is advantageous as it mitigates the use of ligands; the procurable separation of catalyst for recyclability makes the protocol heterogeneous and monetary. MgO NPs gave efficacious catalytic performance towards the desired products due to high surface area. By considering these efficient merits, scientists have focused their attentions towards stupendous applications of MgO NPs in selective organic transformation. In the current review article, we summarized the synthesis of MgO NPs and numerous characterization techniques, whereas the application section illustrates their utility as a catalyst in several organic transformations. We believe this decisive appraisal will provide imperative details to further advance the application of MgO NPs in selective catalysis.

Nickel-phenanthroline Complex Supported on Mesoporous Carbon as a Catalyst for Carboxylation under CO2 Atmosphere

Carbon dioxide is a highly potential renewable C1 source for synthesis of fine chemicals. Utilization of CO2 in carboxylation reactions requires catalysts, such as: nickel complex for CO2 activation. However, the use of homogeneous catalysts in the reaction is still less efficient due to the difficulty of separating the product and catalyst from reaction mixture. Therefore, it is necessary to heterogenize the nickel complex in a solid support such as mesoporous carbon. In this report, mesoporous carbon (MC) prepared from phloroglucinol and formaldehyde through soft template method was used as a solid support for Ni-phenanthroline complex (Ni-phen). The catalyst was characterized by Fourier Transform Infra Red (FT-IR), X-Ray Diffraction (XRD), Scanning Electron Microscope - Energy Dispersive X-Ray (SEM-EDX), and Surface Area Analyzer (SAA). The result of SAA characterization showed that the pore diameter of MC was 6.7 nm and Ni-phen/MC was 5.1 nm which indicates that the materials have meso-size pores. Ni-phen/MC material was then used as a heterogeneous catalyst in the carboxylation reaction of phenylacetylene under an ambient CO2 pressure. The reactions were carried out in several variations of conditions such as temperature, time and catalyst types. Based on the results of the reaction, the best conditions were obtained at 25 °C for 8 h of reaction time using Ni-phen/MC catalyst. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

In Situ Prepared Solar Light-Driven Flexible Actuated Carbon Cloth-Based Nanorod Photocatalyst for Selective Radical-Radical Coupling to Vinyl Sulfides.

A global challenge faced by light harvesting photocatalyst is how to promote the selective organic transformation, such as C-S bond formation via radical-radical coupling under solar light. Here, we report a two-dimensional covalent organic frameworks (2D-COFs), poly (perylene-imide-benzoquinone) nanorod through insitu condensation on flexible activated carbon cloth (PPIBNR-FACC) to function as a light harvester material for highly selective radical-radical coupling to vinyl sulfides (i.e. C-S bond activation). Such a structure supports charge transfer from PPIBNR to FACC, which is essential for the selective radical-radical coupling. Hence, organic transformation is attaining high yields and selectivity (˜99%) under solar light using insitu prepared PPIBNR-FACC photocatalyst. The structural virtues of PPIBNR-FACC will trigger the utmost investigations into designable and versatile 2D-COFs for fine chemical synthesis.

Carbon Molecular Sieve Supported Pd Catalyzed Hydrogenation of Cinnamaldehyde in Alkaline Medium

Synthesis of various fine chemicals and pharmaceuticals are regulated through selective hydrogenation of α,β-unsaturated aldehydes. Hydrocinnamaldehyde is one of the important compounds in perfumery and flavouring industries. It is highly precarious and challenging to control the product selectivity as well as conversion in cinnamaldehyde hydrogenation. In this study, an effective hydrogenation of cinnamaldehyde was attained in presence of aqueous-protic organic medium by utilizing Pd/CMS and other additives of alkali such as K2CO3. The Pd/CMS catalyst along with alkali media catalyzed the hydrogenation of C=C selectively in cinnamaldehyde in order to form hydrocinnamaldehyde with 100% conversion rate. Additionally, the parallel hydrogenation of C=O and C=C bonds in cinnamaldehyde takes place in absence of media. The C=O bond reduction in cinnamaldehyde can be restricted through K2CO3 addition to aqueous-protic solution. The active sites of palladium were found to be uniform and analyzed using HRTEM data. Based on the mechanism involved in micropores of carbon molecular sieves, the key role of promoter is associated with hydrogenation of cinnamaldehyde. The catalytic criterion was appropriate with the acquired activity data.

Systematic engineering of the rate-limiting step of β-alanine biosynthesis in Escherichia coli

Abstract Background Large amounts of β-alanine are required in fine chemical and pharmaceutical synthesis and other fields. Profitable and green methods are required for the industrial production of β-alanine. Results Replacing endogenous panD of Escherichia coli with heterologous CgpanD from Corynebacterium glutamicum enabled β-alanine synthesis of 0.67 g/L by strain B0016-082BB. Overexpressing CgpanD on both plasmids and chromosomes to enhance the rate-limiting step improved the β-alanine titer to 4.25 g/L in strain B0016-083BB/pPL451-panD with a slighter metabolic burden. Growth factors were introduced by addition of yeast extract, and 6.65 g/L of β-alanine was synthesized by strain B0016-083BB/pPL451-panD in the M9-3Y medium. Conclusions Enhancement of the rate-limiting steps in the β-alanine biosynthetic pathway, recruitment of the temperature-sensitive inducible pL promoter, and optimization of the fermentation process could efficiently increase β-alanine production in E. coli. How to cite: Xua J, Zhua Y, Zhou Z. Systematic engineering of the rate-limiting step of β-alanine biosynthesis in Escherichia col. Electron J Biotechnol 2021;51. https://doi.org/10.1016/j.ejbt.2021.03.002.

Heterogenization of a Molecular Ni Catalyst within a Porous Macroligand for the Direct C–H Arylation of Heteroarenes

Direct C–H functionalization catalyzed by a robust and recyclable heterogeneous catalyst is highly desirable for sustainable fine chemical synthesis. Bipyridine units covalently incorporated into the backbone of a porous organic polymer were used as a porous macroligand for the heterogenization of a molecular nickel catalyst. A controlled nickel loading within the porous macroligand is achieved, and the nickel coordination to the bipyridine (bpy) sites is assessed at the molecular level using IR and solid-state NMR spectroscopy. The heterogenized Ni-bpy catalyst was successfully applied to the direct and fully selective C2 arylation of benzothiophenes, thiophene, and selenophene, as well as for the arylation of free NH-indole. Recyclability of the catalyst was achieved by employing hydride activators to reach a cumulative turnover number of more than 300 after seven cycles of catalysis, which corresponds to a total productivity of 12 g of 2-phenylbenzothiophene, chosen as model target biaryl, per gram of catalyst.

Enhanced Performance of Palladium Catalyst Confined Within Carbon Nanotubes for Heck Reaction

Confined carbon nanotubes (CNTs) are typically used to tune the activity and stability of catalysts so as to increase their efficiency. Herein, we compared the catalytic performances of palladium nanoparticles (Pd NPs) located in different regions of CNTs for Heck reaction. The catalyst with Pd NPs located in the internal surface of CNTs (Pd-in-CNT) has a higher reaction rate than that with Pd NPs attached on the external surface of CNTs (Pd-out-CNT). The activity of the Pd-in-CNT is 9.4 times higher than that of Pd-out-CNT in the Heck reaction, possibly because of the smaller particle size and modified redox properties of the confined Pd NPs. The CNT cavities create more active sites, consistenting with a higher microcalorimetric adsorption of carbon monoxide. Leaching of the Pd species during the reactions was observed with both types of catalysts. However, the Pd-in-CNT catalyst showed lower leaching than that of Pd-out-CNT owing to the spatial restriction of the channels in the former. More importantly, these novel catalysts were also used to synthesize a broad range of p-substituted iodobenzene derivatives, affording new and efficient route for the synthesis of valuable fine chemicals via carbon–carbon bond cross-coupling reactions.