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.

This review intends to provide the reader with a clear and concise overview of how preparative continuous flow organic chemistry could potentially impact on current important societal challenges. These societal challenges include health/well‐being and sustainable development. Continuous flow chemistry has enabled significant advances for the manufacturing of pharmaceuticals, as well as for biomass valorization toward a biosourced chemical industry. Examples related to pharmaceutical production are herein focused on (a) the implementation of flow chemistry to reduce the occurrence of drug shortages, (b) continuous flow manufacturing of orphan drugs, (c) continuous flow preparation of active pharmaceuticals listed on the WHO list of essential medicines and (d) perspectives for the manufacturing of peptide‐based pharmaceuticals. Examples related to sustainable development are focused on the valorization of biosourced platform molecules. Besides positive impacts on societal challenges, this review also illustrates some of the potentially most threatening perspectives of continuous flow technology within the actual context of terrorism and drug abuse.

With ever-evolving light-emitting diode (LED) technology, classical photochemical transformations are becoming accessible with more efficient and industrially viable light sources. In combination with a triplet sensitizer, we report the detailed exploration of [2 + 2] cycloadditions, in flow, of various maleic anhydride derivatives with gaseous ethylene. By the use of a flow reactor capable of gas handling and LED wavelength/power screening, an in-depth optimization of these reactions was carried out. In particular, we highlight the importance of matching the substrate and sensitizer triplet energies alongside the light source emission wavelength and power. Initial triplet-sensitized reactions of maleic anhydride were hampered by benzophenone's poor absorbance at 375 nm. However, density functional theory (DFT) calculations predicted that derivatives such as citraconic anhydride have low enough triplet energies to undergo triplet transfer from thioxanthone, whose absorbance matches the LED emission at 375 nm. This observation held true experimentally, allowing optimization and further exemplification in a larger-scale reactor, whereby >100 g of material was processed in 10 h. These straightforward DFT calculations were also applied to a number of other substrates and showed a good correlation with experimental data, implying that their use can be a powerful strategy in targeted reaction optimization for future substrates.

A robust continuous flow procedure for the transformation of bio-based glycerol into high value-added β-amino alcohol active pharmaceutical ingredients.

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A solvent-free organocatalyzed process for the transesterification of dimethyl carbonate (DMC) with 1,2-diols under scalable continuous flow conditions.

Continuous flow preparation of antidepressant ketamine and analogs under sustainable conditions.

Development of a scalable continuous-flow process towards enriched threo-methylphenidate (Ritalin) hydrochloride.