Basic Anion-Exchange Resin-Catalyzed Aldol Condensation of Aromatic Ketones with Aldehydes in Continuous Flow

Structure-Directed Quaternary Ammonium Hydroxide Resins: High-Performance Heterogeneous Base Catalysts for Continuous-Flow Carbon-Carbon Bond-Forming Reactions

Quaternary ammonium hydroxide resins are widely recognized for their effectiveness as immobilized bases and are frequently utilized as commodity chemicals for anion-exchange applications. However, despite their accessibility, chemically controlling their properties has proven challenging, hindering research and development efforts toward their use as solid base catalysts. This study investigates the synthetic factors that are crucial for achieving high functional performance in polystyrene resins. Using commercially available resin as a benchmark and the continuous-flow Henry reaction as a model system, we explore and evaluate newly synthesized resin catalysts to maximize their basic catalytic activity.

Migration from Photochemistry to Electrochemistry for [2 + 2] Cycloaddition Reaction

Cyclobutane scaffolds are incorporated in several valuable natural and bioactive products. However, non-photochemical ways to synthesize cyclobutanes have scarcely been investigated. Herein, based on the principles of the electrosynthesis technique, we introduce a novel electrochemical approach for attaining cyclobutanes by a simple [2 + 2] cycloaddition of two electron-deficient olefins in the absence of photocatalysts or metal catalysts. This electrochemical strategy provides a suitable condition for synthesizing tetrasubstituted cyclobutanes with a variety of functional groups in good to excellent efficiency, compatible with gram-scale synthesis. In contrast to previous challenging methods, this approach strongly focuses on the convenient accessibility of the reaction instruments and starting materials for preparing cyclobutanes. Readily accessible and inexpensive electrode materials are firm evidence to prove the simplicity of this reaction. In addition, mechanistic insight into the reaction is obtained by investigation of the CV spectra of the reactants. Also, the structure of a product is identified by X-ray crystallography.

Modeling Temperature and Species Concentration Profiles on a Continuous-Flow Reactor Applied to Aldol Condensation

This paper presents the modeling of a continuous-flow reactor used for the synthesis of organic products. The finite element method software, COMSOL Multiphysics, was used to model transport phenomena and reaction kinetics. The temperature is one of the most important kinetic factors that may modify the reaction. A rise in temperature can generate a positive reaction but also secondary side reactions. The design of our system and of many other continuous systems makes it impossible, however, to measure the temperature throughout the reactor. In this paper, we modeled the temperature profile within the reactors as a function of the flow rate, temperature set point, and type of reactor material. The results demonstrated that although it is not a good thermal conductor, polytetrafluoroethylene can be used like other materials. The desired temperature was not reached for any of the reactor material likely to affect the product yield. The model gave the residence time required to reach the stabilized temperature. The comparison of calculated and experimental values of outlet temperature showed good agreement, with a maximum relative difference of only 5%. Knowledge of the temperature profile made it possible to control the concentration distribution of the chemical species in the reactor. The aldol condensation was chosen to determine the kinetic parameters of this reaction as the products of this reaction are found in many natural molecules and drugs. To integrate the chemical model, the kinetic parameters were determined by using experimental data. An equilibrium concentration of 0.2 mol/L was found with initial reactant concentrations of 0.45 mol/L. The chemical modeling gave the species concentrations throughout the reactor. Calculated concentrations were in good agreement with experimental data, with a maximum relative difference of less than 9%. By modeling this reaction, the reaction yield as a function of reactant concentration, temperature, and residence times was estimated.

Aerobic oxidation of alcohols enabled by nitrogen-doped copper nanoparticle catalysts

Heterogeneous nitrogen-doped carbon-incarcerated copper nanoparticle catalysts have been developed.

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

Due to their intrinsic physical properties, which includes being able to perform as volatile liquids at room and biological temperatures, fragrance ingredients/intermediates make ideal candidates for continuous-flow manufacturing. This review highlights the potential crossover between a multibillion dollar industry and the flourishing sub-field of flow chemistry evolving within the discipline of organic synthesis. This is illustrated through selected examples of industrially important transformations specific to the fragrances and flavours industry and by highlighting the advantages of conducting these transformations by using a flow approach. This review is designed to be a compendium of techniques and apparatus already published in the chemical and engineering literature which would constitute a known solution or inspiration for commonly encountered procedures in the manufacture of fragrance and flavour chemicals.

Evolution of flow-oriented design strategies in the continuous preparation of pharmaceuticals

This review focuses on the flow-oriented design (FOD) in the multi-step continuous-flow synthesis of active pharmaceutical ingredients.