Journal of Flow Chemistry最新文献

Sustainable synthesis of acrolein, a key chemical intermediate, from biomass-derived glycerol is highly attractive. However, conventional catalysts for the dehydration of glycerol suffer from low acrolein selectivity and high deactivation tendency. Herein, a novel green catalyst (HPW/T_0.6 S-COOH) was prepared and employed in the dehydration of glycerol in a continuous flow reactor. The performance of different catalysts and the effects of reaction conditions (reaction temperature, N₂ flow rate, and glycerol concentration) were examined. The HPW/T_0.6 S-COOH catalyst provides the best glycerol conversion of 96.38% and acrolein selectivity of 92.01%. The NH₃-TPD and pyridine-FTIR results indicate that the Brønsted acid site is more susceptible to acrolein, while the weak strength acid site effectively prevents the further reaction of acrolein, providing practical insights for the rational design of efficient and continuous synthesis of acrolein catalysts.

A continuous flow approach for the generation of phenyl glucosazone from glucose and phenyl hydrazine is reported giving the pure target in 53% isolated yield. This thermal process generates the target product as an insoluble material that causes reactor fouling via adhering to the reactor walls. To overcome this issue a segmented flow approach was realised whereby streams of air and the reaction solution were combined in a T-piece and directed through the heated reactor coil. The resulting micro-mixing prevented reactor fouling and blocking and allowed for multi-hour reactions to generate the desired target in high yield. The value of the phenyl glucosazone product was demonstrated via its oxidative cyclisation into 2H-phenyl-1,2,3-triazoles which represent important heterocyclic scaffolds.

The design and implementation of flow technique helps organic chemists to resolve numerous challenges that are encountered during various catalytic reactions. Flow technologies, which offer solutions for technical and/or chemical issues, have gained popularity over the last two decades in the field of organic chemistry. The selectivity, efficiency, and safety of the entire process has been accelerated by flow reactors as they improve mass and heat transfer, speeds up the mixing of the reaction, and they offer exact control of the reaction parameters. This review mainly describes the utilization of flow chemistry in reactions involving organiozinc reagent, particularly Negishi coupling. The Negishi coupling of organozinc reagent is a valuable tool for the formation of C-C bond with functional group tolerance and are used extensively in total synthesis. This review also portrays a comparative study of organozinc reagents prepared using different procedures. A study of the effect of different catalysts over the same reaction is also carried out. An overview of different flow techniques that are employed has also been incorporated.

Organolithium compounds have been used successfully in flow chemistry since the recent past. Most of the studies dealt with the use in halogen-lithium exchanges. So far, however, there has been a lack of use in substitution reactions. The use of flow microreactors makes the highly reactive organolithium compounds more controllable and thus creates new synthetic possibilities.

The synthesis of dithiocarbamates derivatives is important for their practical utilization as pharmaceuticals and for other purposes. Herein, we demonstrated the TfOH-catalyzed synthesis of dithiocarbamates via three-component reaction of α-diazoesters in good yields under continuous flow conditions. The reaction exhibits a wide substrate scope of diazo compounds and high functional group tolerance. This study provides a safe and mild protocol to form dithiocarbamates that complements TfOH-catalyzed S-H insertion reaction of diazo compounds and continuous flow synthesis strategies.

Phenols are vital building blocks for manufactured goods, agrochemicals, and medicine. As the demand to circumvent fossil fuels intensifies, so does the need to establish alternate sources of chemical feedstock, with many researchers looking to biomass. Lignin, a complex biopolymer found in plants, represents a relatively untapped renewable source of phenolic compounds. Examples of aromatic compounds derived from lignin include phenol, guaiacol (2-methoxyphenol), and catechol (2-hydroxyphenol). The development of new technologies and chemistry to upgrade or modify these compounds is crucial to realizing the potential of biomass as chemical feedstock. Over the last two decades, continuous flow technology has become an established tool for chemists to expand the capabilities of reaction control and to provide a means to probe novel reactions that might otherwise be difficult to study or accomplish via conventional means. Flow also imparts many advantages, such as superior mixing capabilities for gas/liquid reactions, increased efficiency for photochemical transformations, and improved scalability. This mini review will highlight research efforts reported in the last half-decade (since 2016) toward upgrading lignin-derived phenolic substrates using continuous flow technology. Recent developments focus on reactions requiring oxygenation, oxidation, hydrogenation, and deoxygenation to name a few.

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Water soluble biomimetic models of Riboflavin (B2 vitamin) and Folic acid (B8 vitamin) demonstrated to be good oxidant of formic acid at various pH. Their usage as anolyte mediators in a flow fuel cell to convert formic acid (or formate) into electricity is validated with measured power densities up to 16 mW.cm^− 2. These preliminary optimum conditions demonstrated a volumetric energy density of 0.68 Wh.L^− 1 when operating at 5 mA.cm^− 2 and neutral pH. These new conditions inspired from redox flow batteries processes permit to remove noble metals at both sides of the formate flow fuel cell.

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