Journal of Flow Chemistry最新文献

The direct conversion of glucose to 5-(hydroxymethyl)furfural (HMF) has been considered a challenging process. In this study, we developed a new method using gadolinium(III) trifluoromethanesulfonate (Gd(OTf)₃) in combination with Brønsted acidic ionic liquids as a catalytic system to search possibly more environmentally benign process. The reaction was carried out under a continuous-flow system. The one-step isomerization/dehydration of glucose to give the highest HMF with Gd(OTf)₃ together with DBU-based Brønsted acidic ionic liquid in a low-cost home-built continuous system. The plausible mechanism was proposed with the Lewis acidic sites of Gd(OTf)₃ for the isomerization step and DBU-based Brønsted acidic ionic liquid sites for the dehydration step. The recycling of catalytic system Gd(OTf)₃/DBU-based Brønsted acidic ionic liquid in DMSO was examined. Our findings provided a safe and environmental process for the continuous conversion of glucose into HMF. The use of continuous flow for HMF synthesis ensures that the current method can be applied to the large-scale process.

Biomass is a renewable, almost infinite reservoir of a large diversity of highly functionalized chemicals. The conversion of biomass toward biobased platform molecules through biorefineries generally still lacks economic viability. Profitability could be enhanced through the development of new market opportunities for these biobased platform chemicals. The fine chemical industry, and more specifically the manufacturing of pharmaceuticals is one of the sectors bearing significant potential for these biobased building blocks to rapidly emerge and make a difference. There are, however, still many challenges to be dealt with before this market can thrive. Continuous flow technology and its integration for the upgrading of biobased platform molecules for the manufacturing of pharmaceuticals is foreseen as a game-changer. This perspective reflects on the main challenges relative to chemical, process, regulatory and supply chain-related burdens still to be addressed. The implementation of integrated continuous flow processes and their automation into modular units will help for tackling with these challenges.

Graphical abstract

We presented a microfluidic device for the preparation of monodisperse microdroplets with a small volume of samples or reagents, which is power-free, user-friendly and based only on a highly portable syringe. Our method requires only hand-operated syringes and sharpened capillaries without any complicated experimental setups, making the entire system portable and user-friendly for non-technical users. Vacuum is generated by pulling the plunger of the syringe on site, and fluid is generated by vacuum. The droplet size can be flexibly controlled by adjusting the size of micropores and capillary or vacuum degree. More potentially, microliter samples or reagents can also be prepared from it into emulsions. Unlike traditional methods, our device is self-activated, avoiding the need for external power supply while ensuring fewer samples or reagents consumption, simplifying operations and saving costs, facilitating immediate diagnostic testing or field trace substance detection.

Benzodiazepines possess a wide spectrum of valuable pharmacological effects and are among the leading drugs, commonly prescribed ones for various pathologies. Herein we describe the continuous flow synthesis of six benzodiazepines from aminobenzophenones: diazepam, fludiazepam, nordazepam, nitrazepam, clonazepam, oxazepam.

N-(3-Amino-4-methylphenyl)benzamide (1) is a crucial building blocks of many drug candidates. In this paper, a continuous flow microreactor system was developed to synthesize 1 and determine intrinsic reaction kinetics parameters. By screening the acylating reagents and reaction conditions, 1 was obtained by the selective acylation of 4-methylbenzene-1,3-diamine (2) with benzoic anhydride (3). Since the two amine groups in 2 are in different chemical environments, parallel by-products and serial by-products coexist, which makes the selective monoacylation process relatively complicated. To reveal the reaction process clearly, reaction rate constants and their 95% confidence intervals, activation energies, pre-exponential factors were acquired by kinetics study in microflow system. The established kinetic model can calculate the selectivity and conversion of the acylation reaction, which are in good agreement with the experimental results. Subsequently, the kinetic model was used to optimize reaction conditions, as a result, 1 was synthesized in the microreactor with a yield of 85.7% within 10 min.

The nitration reaction and purification process of 2-Ethyl-1-hexanol is highly hazardous and characterized by severe thermal instability. Therefore, appropriate safety and kinetics studies are needed to promote safe synthesis in chemical production. However, obtaining accurate kinetic data is challenging due to its fast, highly exothermic, and heterogeneous characteristics. In this study, we obtained reaction kinetic parameters of 2-Ethyl-1-hexanol in a capillary-microreactor at different sulfuric acid concentrations and temperatures and calculated the per-exponential factor and activation energy. The thermal stability of 2-Ethylhexyl nitrate in mixed acids was determined by differential scanning calorimetry. Computational Fluid Dynamics was used to simulated the temperature distribution inside the capillary-microreactor for a T-shaped structure based on the kinetic and thermal stability data. The results show that even small-scale reaction tubes produce hot spots in the reactor inlet region in an isothermal environment. Under adiabatic conditions, the temperature inside the capillary is close to the decomposition temperature of the acid mixture. Therefore, the thermal safety of nitration reactions, even in small-scale microreactor systems, cannot be ignored. The results of this study have important implications for the industrial process design and safety for highly-exothermic reactions.

Graphical abstract

Resveratrol is a natural bioactive non-flavonoid polyphenol that protects from cardiovascular disease, neurodegenerative diseases and various cancers. Unfortunately, the amounts of resveratrol in plants are low and therefore, chemical synthesis is still the main way to obtain this valuable structure. In this work, Wittig reaction was chosen as the synthetic route for the study on technology influence in batch vs. micro- or milliflow reactors during the production of new resveratrol-like compounds. A series of reactions was carried out by batch synthesis, and intensified in a milli- and a microreactor, changing the reaction conditions to increase the efficiency and productivity of the process. Results were compared based on conversion, yield, productivity and trans/cis ratio. Similar yields and conversions were obtained in all reaction systems, but in much shorter time in the milli- and microscale compared to the batch reactor. On the other hand, higher productivities were obtained in the millireactor and microreactor, making them better systems for the proposed reactions of new heterocyclic resveratrol analogues synthesis.

Graphical abstract