Journal of Flow Chemistry最新文献

Recent developments in automated flow chemistry for pharmaceutical compound synthesis have garnered significant attention. Automation in synthesis represents a cutting-edge frontier in the field of chemistry, offering highly efficient, rapid, and reproducible synthetic methods that significantly shorten reaction time and reduce costs. In the realm of pharmaceutical compound synthesis, automated flow chemistry demonstrates unique importance. By utilizing flow chemistry, reactions can be performed under continuous flow conditions, enabling precise reaction control, higher yields, and increased product purity. Additionally, automated flow synthesis overcomes several challenges encountered in traditional batch synthesis, such as decreased generation of chemical waste, optimization of reaction conditions, and enhanced operational safety. This review highlights the recent developments in automated flow synthesis of various pharmaceutical compounds, including large biopharmaceutical molecules, small organic drug molecules, and carbohydrates. It covers automated iterative synthesis and the use of machine learning to enhance synthesis efficiency. Furthermore, it explores the practical application of high-throughput synthesis and screening technologies. Finally, the review offers concise perspectives on potential future developments in the field.

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The development of automated flow synthesis kept breaking through new challenges for chemical reactions. Especially with the increasing demand for fast and efficient synthesis of therapeutic compounds, automated systems built a solid foundation for pharmaceutical innovation.

Solid-phase flow synthesis has been well-developed in the synthesis of large biopharmaceutical molecules; the immobilized support helps replace tedious separation and purification with a simple solvent wash. Additionally, flow-based pathways could provide convenience for automation.

High-throughput synthesis with in-line analysis offers both high-efficiency production and accurate monitoring. Therefore, this combination could be easily applied to rapid screening processes for building a large library, enhancing the performance of machine learning in reaction, and product prediction.

Artificial intelligence can be applied to self-optimized synthesis processes. Algorithm-based software could rapidly calculate and optimize insufficient reactions with a learning model built on past reactions posted in the literature. The connected robotic arm can then be automatically set to perform the optimized reaction.

Flow biocatalysis has emerged as an empowering tool to boost the potential of enzymatic reactions towards more automatized, sustainable, and generally efficient synthetic processes. In the last fifteen years, the increasing number of biocatalytic transformations carried out in continuous flow exemplified the benefits that this technology can bring to incorporate biocatalysis into industrial operations. This perspective aims to capture in a nutshell the available methodologies for flow biocatalysis as well as to discuss the current limitations and the future directions in this field.

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An automated flow chemistry platform for DNA-encoded library (DEL) technologies requires the integration of a purification process for DNA-tagged substrates. It facilitates the development of further DEL reactions, building block rehearsal, and library synthesis. Therefore, a recently developed, manual affinity-based batch purification process for DNA-tagged substrates based on dispersive solid-phase extraction (DSPE) was transferred to automated flow chemistry using tailored 3D-printed microfluidic devices and open-source lab automation equipment. The immobilization and purification steps use Watson–Crick base pairing for a compound-encoding single-stranded DNA, which allows for the thorough removal of impurities and contaminations by washing steps and operationally simple recovery of the purified DNA-encoded compounds. This work optimized the annealing step for flow incubation and DNA purification was accomplished by flow DSPE washing/elution steps. The manually performed batch affinity-based purification process was compared with the microfluidic process by determining qualitative and quantitative DNA recovery parameters. It aimed at comparing batch and flow purification processes with regard to DNA recovery and purity to benefit from the high potential for automation, precise process control, and higher information density of the microfluidic purification process for DNA-tagged substrates. Manual operations were minimized by applying an automation strategy to demonstrate the potential for integrating the microfluidic affinity-based purification process for DNA-tagged substrates into an automated DNA-encoded flow chemistry platform.

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Microchemical technology is an advanced chemical production technology and the large-scale production for industrial applications is realized by parallelization of microchannels. In this paper, the emulsification process and numbering-up of droplets in asymmetric parallelized microchannels with T-junction are investigated, and the effects of fluid properties and operating conditions on droplet size are analyzed. The droplet generation process is divided into waiting stage, filling stage, necking stage, and pinch-off stage, according to the variation of the characteristic length scale during droplet generation. The flow patterns of droplet swarm in cavities and their influence on fluid distribution are analyzed. The droplet size prediction equation and fluid distribution model in asymmetric parallelized microchannel are constructed. The phenomenon of droplet asynchronous generation due to the coupling of parallelized microchannels during the numbering-up process is analyzed. The effect of asynchronous generation on droplet monodispersity is investigated and the mothod for the prevention of this effect is proposed.

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Continuous flow technology has been widely adopted in manufacturing active pharmaceutical ingredients (APIs). Herein, we report an expeditious multi-step continuous-flow strategy for an efficient and highly productive flow synthesis of 7-methoxy-1-tetralone, which is an essential intermediate for the opioid analgesic drug (-)-dezocine. Compared with the traditional batch operation, this work presents significant advantages of continuous-flow chemistry with dramatically reduced reaction time, highly improved reaction efficiency, good controls over reaction optimizing conditions, etc. The flow protocol in this work provided the desired product in an overall yield of up to 76.6% with 99% purity, much higher than those from batch process (i.e., 50% yield, 92% purity). Moreover, reaction efficiency is highly improved with a throughput of 0.49 g/h, the total reaction time is markedly reduced from hours in batch to minutes in flow process.

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Hazardous reagents such as sulfur dioxide (SO₂) and chlorine (Cl₂) are powerful and atom-efficient reagents for respectively introducing the ‘SO₂’ moiety and ‘Cl’ atom into organic molecules. However, their use is limited due to a lack of protocols and methods to access them in laboratories readily. This article describes the development of a prototype, method, and process for accessing hazardous gaseous reagents safely on demand continuously for further utilization in organic synthesis. The prototype was validated by producing SO₂ from readily accessible laboratory reagents sodium sulfite (Na₂SO₃) and sulfuric acid (H₂SO₄). The generated SO₂ was successfully utilized for the synthesis of aryl sulfinate salts, which were subsequently converted to sulfonamides and sulfone-containing bicalutamide drugs. The broader applicability of the reactor prototype has also been demonstrated in the generation of chlorine gas from bleach (NaOCl) and hydrochloric acid (HCl), followed by the separation of chlorine gas from an acidic aqueous reaction mixture. The utilization of the separated chlorine gas was demonstrated in the synthesis of silyl chlorides in both batch and continuous manners. The present reactor prototype not only enables safe and convenient access to highly hazardous gaseous reagents for facile organic synthesis in laboratories, but also eliminates the risks in handling, storage, and transportation of hazardous gaseous reagents in cylinders.

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Catalytic enantioselective Strecker reactions on an achiral substrate using sub-stoichiometric amounts of a chiral catalyst represent an evolving key strategy for the effective synthesis of α-amino nitriles. We herein disclosed the set-up of a flow-based methodology for enantioselective Strecker, employing ethyl cyanoformate as a relatively safe cyanide source, a cinchona-based catalyst, and methanol as additive. A thorough exploration of key parameters allowed the identification of the most efficient reagent mixing mode, the optimum solvent for the flow synthesis, minimum catalyst loading, additive, temperature, and residence time. The newly developed method allows straightforward reaction channeling towards the fast and complete formation of the α-amino nitrile products, thus reducing the yield drop due to indolenine degradation during long-lasting batch-wise reactions. Moreover, we herein provide preliminary hints for sustainability, by proposing a simple procedure for catalyst recycling, thus opening the way for further optimization of the proposed methodology.

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A high-temperature continuous flow protocol is reported for the intensified synthesis of an important industrial raw material via aromatic Claisen rearrangement of the corresponding diallyl ether precursor. The process takes advantage of solvent-free conditions, thereby maximizing productivity whilst reducing cost and environmental impact. By precise control over reaction temperature and residence times, a high-yielding and selective synthesis is achieved that ensures improved safety and scalability of the exothermic transformation compared with earlier batch methodologies.

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A low-cost 3D printed standardized flow-photochemistry setup has been designed and developed for use with a pressure-driven flow system using photochemistry lamps available in most laboratories. In this research, photochemical reactors were 3D printed from polypropylene which facilitated rapid optimization of both reactor geometry and experimental setup of the lamp housing system. To exemplify the rapidity of this approach to optimization, a Kessil LED lamp was used in the bromination of a range of toluenes in the 3D printed reactors in good yields with residence times as low as 27 s. The reaction compared favorably with the batch photochemical procedure and was able to be scaled up to a productivity of 75 mmol h⁻¹.

A flow chemistry based continuous morphology-controllable precipitation strategy was successfully developed for synthesis of europium oxalate hydrate microparticles. The effects of flow ratio between raw materials within microchannels on the crystal structure, morphology and particle size distribution of the precipitated products were firstly studied. The results shown that both high yield and controllable morphology were achieved for Eu³⁺ precipitation reactions under its low concentration condition. The effects of supersaturation, mixing intensity, and reaction temperatures were also investigated in detail, which proved the continuous preparation of layered microparticles with concentrated size distribution can be achieved by this strategy. Multiple characterizations and comparison experiment synergistically reveal that the feed flow ratios of nitric acid and oxalic acid determines the morphology and particle size distribution due to affecting the mixing degree and phase composition of the precipitation reaction. In addition, the phase and morphology conversion of precipitates after calcination treatment were also studied, the as-calcined metal oxide powder exhibited a decent photoluminescence characteristic. In summary, this work demonstrates a promising precipitation strategy within micro-channels for mass controllable production of high-quality metal oxide materials.

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