Flow: Chemistry Unatainable by Batch and Dangerous Reactions Made Safe

Two back-to-back articles should be at the top of your list of reading if you are new to continuous flow chemistry or looking into how to generate a method for a selected transformation. These can be found in Specialty Chemicals Magazine May 2014, with Mark Bratt and Ollie Tames of IntensiChem  pp. 42-44– and Gyorgy Dorman and Richard Jones of ThalesNano pp. 45-47.

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The first article is on the fundamental thinking that goes along in flow chemistry and how it is different than the traditional batch model. Mark and Ollie take us through a storyline where chemists tend to use batch process in their strategies in developing flow methods. Their discussion leads into batch reactions that simply aren’t very good and for a number of different reasons….as opportunities were continuous flow methods would have better potential as a process. Examples with fixed bed catalysis and hydrogenations pop out as the examples that one would like to see, but several factors on temperature and pressure expands the capability some batch process simply can’t carry without major equipment by comparison. Read through several of the examples indicating opportunities where batch processes don’t measure up.

The next phase of the article is spent on the mindset — optimized batch processes have been used from optimized chemistry and that had worked very well for things done. For flow, this is a possibility for industries and reactions where the chemistry is not so well worked out — and how the flow process development can be much more streamlined and provide data and feasibility in a more efficient manner. Mark and Ollie walk us through the differences — flow requires different solutions for different schemes — with in-line analytical techniques, these development times could be lowered considerably…..again the comparisons are made with batch processes and industries involved, which gives us a clearer view of where some of the challenges exist. —- Thanks for the perspective Mark and Ollie!

The second article sets the tone by laying out some specs that are present in modern day flow instrumentation to go along with the reproducibility, speed and telescoping capability. But quickly switching gears, Gyorgy and Richard paint a picture of why flow should be used in place of some of our older techniques with dangerous reactions and reagents — just think about all of the news today on safety and explosion examples in our field. If for no other reason than this, the investment pays for itself on the first level in academia and industry. Since Gyorgy and Richard categorized a number of examples: high temperature thermal cyclizations, hydrogenations, diazotizations, low-temperature transformations, gas-liquid reactions, etc., I will leave you with the article to read. The importance of the article is that is helps provide a complete picture of using this technology in fields where small molecule heterocyclic chemistry is used, be it specialty chemicals or bench medicinal chemistry. Each category shows important parameters that can be utilized in flow to keep a clean, safe operation of reactions that have special conditions when used in a batch format. Thanks for the perspective Gyorgy and Richard