Application of reactor engineering concepts in continuous flow chemistry: a review

The adoption of flow technology for the manufacture of chemical entities, and in particular pharmaceuticals, has seen rapid growth over the past two decades with the technology now blurring the lines between chemistry and chemical engineering.

Flow Chemistry for Cycloaddition Reactions

Continuous flow reactors form part of a rapidly growing research area that has changed the way synthetic chemistry is performed not only in academia but also at the industrial level. This Review highlights the most recent advances in cycloaddition reactions performed in flow systems. Cycloadditions are atom-efficient transformations for the synthesis of carbo- and heterocycles, involved in the construction of challenging skeletons of complex molecules. The main advantages of translating these processes into flow include using intensified conditions, safer handling of hazardous reagents and gases, easy tuning of reaction conditions, and straightforward scaling up. These benefits are especially important in cycloadditions such as the copper(I)-catalyzed azide alkyne cycloaddition (CuAAC), Diels-Alder reaction, ozonolysis and [2+2] photocycloadditions. Some of these transformations are key reactions in the industrial synthesis of pharmaceuticals.

Continuous Flow Upgrading of Selected C2-C6 Platform Chemicals Derived from Biomass

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C₂ to C₆ bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

Flow Chemistry in Contemporary Chemical Sciences: A Real Variety of Its Applications

Flow chemistry is an area of contemporary chemistry exploiting the hydrodynamic conditions of flowing liquids to provide particular environments for chemical reactions. These particular conditions of enhanced and strictly regulated transport of reagents, improved interface contacts, intensification of heat transfer, and safe operation with hazardous chemicals can be utilized in chemical synthesis, both for mechanization and automation of analytical procedures, and for the investigation of the kinetics of ultrafast reactions. Such methods are developed for more than half a century. In the field of chemical synthesis, they are used mostly in pharmaceutical chemistry for efficient syntheses of small amounts of active substances. In analytical chemistry, flow measuring systems are designed for environmental applications and industrial monitoring, as well as medical and pharmaceutical analysis, providing essential enhancement of the yield of analyses and precision of analytical determinations. The main concept of this review is to show the overlapping of development trends in the design of instrumentation and various ways of the utilization of specificity of chemical operations under flow conditions, especially for synthetic and analytical purposes, with a simultaneous presentation of the still rather limited correspondence between these two main areas of flow chemistry.

In-Line Purification: A Key Component to Facilitate Drug Synthesis and Process Development in Medicinal Chemistry

In-line purification is an important tool for flow chemistry. It enables effective handling of unstable intermediates and integration of multiple synthetic steps. The integrated flow synthesis is useful for drug synthesis and process development in medicinal chemistry. In this article, we overview current states of in-line purification methods. In particular, we focus on four common methods: scavenger column, distillation, nanofiltration, and extraction. Examples of their applications are provided.