Scale-up Study of Benzoic Acid Alkylation in Flow: From Microflow Capillary Reactor to a Milliflow Reactor

A strategy for the controllable generation of organic superbases from benchtop-stable salts

Organic superbases are a distinct class of strong base that enable numerous modern reaction applications. Despite their great synthetic potential, widespread use and study of superbases are limited by their air sensitivity and difficult preparation. To address this, we report air-stable carboxylate salts of BTPP and P2-t-Bu phosphazene superbases that, when added to solution with an epoxide, spontaneously generate freebase. These systems function as effective precatalysts and stoichiometric prereagents for superbase-promoted addition, substitution and polymerization reactions. In addition to improving the synthesis, shelf stability, handling and recycling of phosphazenes, this approach enables precise regulation of the rate of base generation in situ. The activation strategy effectively mimics manual slow addition techniques, allowing for control over a reaction's rate or induction period and improvement of reactions that require strong base but are also sensitive to its presence, such as Pd-catalyzed coupling reactions.

Design, Heat Transfer, and Visualization of the Milli-Reactor by CFD and ANN

This paper proposes a milli-reactor design method incorporating reactor runaway criteria. Based on Computational Fluid Dynamic (CFD) simulation, neural networks are applied to obtain the optimal reactor structure according to the target reaction requirements. Varma’s theory, the critical Nusselt number for stable operation of the flow reactor, is derived. Inserts of the multi-blade structure are designed and investigated to enhance mixing and heat transfer performance. The flow field and heat transfer capacities are obtained by CFD calculations in the range of Re 50–1800. The internal components increase the heat transfer performance up to 21 times, and the pressure drop up to 16 times. The inclined angle of the blade is recommended to be 45°, which can effectively improve heat transfer without generating excessive pressure drop. By partial least squares regression (PLS) analysis, Re and the number of blades are the most critical factors affecting heat transfer, and the five blades and smaller tilt angles are recommended. The CFD calculation results are in good agreement with the Particle Image Velocimetry (PIV) experimental results.

Recent Progress on Photocatalytic Synthesis of Ester Derivatives and Reaction Mechanisms

Esters and their derivatives are distributed widely in natural products, pharmaceuticals, fine chemicals and other fields. Esters are important building blocks in pharmaceuticals such as clopidogrel, methylphenidate, fenofibrate, travoprost, prasugrel, oseltamivir, eszopiclone and fluticasone. Therefore, esterification reaction becomes more and more popular in the photochemical field. In this review, we highlight three types of reactions to synthesize esters using photochemical strategies. The reaction mechanisms involve mainly single electron transfer, energy transfer or other radical procedures.

Continuous flow chemistry: where are we now? Recent applications, challenges and limitations

A general outlook of the changing face of chemical synthesis is provided in this article through recent applications of continuous flow processing in both industry and academia. The benefits, major challenges and limitations associated with the use of this mode of processing are also given due attention as an attempt to put into perspective the current position of continuous flow processing, either as an alternative or potential combinatory technology for batch processing.