Editorial – Flow Chemistry and Catalysis

While continuous chemical processing, often using immobilised catalysts, has long been conducted on scale, a revolution is underway to bring some of the concepts and technology to the research environment. Indeed, there is a need for synthesis chemists to respond effectively to the Green Agenda as they become increasingly aware of environmental issues and impacts of their work. In particular, how machinery can help alleviate the labour intensive practices of reaction and catalyst optimisation, downstream processing and scale up of routine and repetitive tasks, thereby helping to maximise the human resource by creating time to better plan and discover new chemical reactivity.

Flow chemistry techniques have a proven track record of success especially when handling hazardous or obnoxious material safely. Greater process windows providing access to high temperatures and pressures are available to the new generation devices. Given that improved monitoring feedback and control is possible, we are witnessing great improvements in the robustness of chemical processing in many different environments from pharmaceuticals, agro chemicals, fragrances and materials of all kinds.

Synthesis on demand and even multi-step complex reaction telescoping is becoming common place and is helping to incentivise the new workforce. The collection of papers in this themed issue amply demonstrates the growing interest in catalytic processes that benefit from continuous flow methods. The papers encompass insights into photoredox chemistry, use of reactive gases, solid phase reactions and a magnitude of metal-based catalysis. The diversity of scale and versatility of the systems is truly impressive, as is the wide range of applications described.

As we become more familiar with the power that comes from the use of cheap microprocessors and the ability to control a multitude of devices remotely through the Internet, we can become more innovative and creative with our experiments and approach to chemistry. The amount of digital information that can be collected leads us naturally towards the use of the cloud and machine learning techniques, such as neural networking, for data interpretation and analysis. Future developments in these areas will greatly assist chemists with their work, pointing out data points of interest for further investigation that could provide new leads for target molecules or even reactivity.

Self-optimisation and novel reaction prediction algorithms, along with virtual and augmented reality are all part of this developing synthesis chemistry community. Computational screening for function and the discovery of new reactivity moves us beyond where we are today. Indeed, these advances help us provide better continuity across our different working environments moving towards a more holistic systems approach to synthesis. Chemists will approach problems using an increasingly diverse mind-set, integrating information gleaned from calculations with traditional synthesis knowledge before conducting machine-assisted experiments. Moving forward we can expect even higher levels of monitoring and reaction autonomy that will lead to improved reaction audit trails and greatly enhanced safety characteristics of processes, such as remotely-operable shutdown sequences.

Both homogeneous and heterogeneous catalytic processes, especially those leading to exotherms or where catalyst recycling is imperative, fit nicely into these new continuous flow chemistry paradigms. Increasingly also we believe the physical form, size and aggregation of catalysts will play a bigger role in their selection for ever more demanding applications. This combined with the dynamics imposed by the flow chemistry equipment opens up new opportunities that are difficult, if not impossible, to reproduce by batch mode processing.

Synthesis into the future needs to embrace all these changes and learn how best to integrate flow and batch techniques particularly using a machine-assisted approach. Our laboratories are evolving rapidly and new discoveries and modern technologies are arising via greater collaboration across traditional boundaries between chemists, chemical engineers, informaticians, computational scientists, statisticians, robotics engineers and software developers. No longer will the research carried out by a scientist be largely limited to a single area; increasingly as fields become more entwined, researchers will draw from other expertise to facilitate advances of their work. The themed articles in this issue nicely complement these concepts and we can look forward to continued vibrant activity in this area of research.

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